Research institutions tout the value of scholarship that crosses disciplines – but academia pushes interdisciplinary researchers out

Source: The Conversation – USA – By Bruce Weinberg, Professor of Economics, The Ohio State University

Interdisciplinary researchers are trained to conduct work that crosses between fields. PixelsEffect/E+ via Getty Images

The most exciting landmark scientific achievements don’t happen without researchers sharing and collaborating with others outside their field. When people first landed on the Moon in 1969, Neil Armstrong’s first footsteps marked the realization of a century-long vision that integrated a variety of scientific fields. Landing on the Moon required expertise in electrical, mechanical, chemical and computer engineering, as well as astronomy and physics.

Similarly, the advances in genetics that have made the biotechnology revolution possible involved contributions from disciplines as far ranging as biology, mathematics and statistics, chemistry and computer science.

Today, some of the biggest challenges that scientists face are interdisciplinary in nature – from studying the effects of climate change to managing generative artificial intelligence.

Climate change isn’t only an environmental problem, just like the impact of AI isn’t solely technological. Scientists in a variety of disciplines can independently come up with ways to examine these issues, but as research has shown, the most effective approaches often integrate multiple fields.

Our own interdisciplinary team of researchers in economics and informatics – itself an interdisciplinary field focused on technology, information and people – explored the career hurdles that many interdisciplinary researchers face in a study published in July 2024. We studied how these challenges affect their careers and the production of interdisciplinary research.

Infrastructure and interdisciplinary work

Government and private funders alike have introduced programs to support interdisciplinary work. Universities foster interdisciplinary research through joint appointments, hiring multiple faculty at once, centers that span disciplines, and graduate programs that join different fields.

With these efforts, you might expect a high demand and exceptional career outcomes for interdisciplinary researchers. However, this does not appear to be the case. The American academic system is still very much dominated by disciplines and academic departments. A researcher whose work doesn’t fit neatly into a category can easily fall through the cracks.

The structure of distinct disciplines and departments is deeply embedded in universities. Many researchers have trouble finding a journal willing to publish interdisciplinary papers or a department willing to offer interdisciplinary classes. Students interested in this work have difficulty finding mentors.

Interdisciplinary researchers may have a harder time publishing their work.
Maggie Villiger, CC BY-ND

When interdisciplinary researchers apply for jobs, promotion and tenure, hiring committees made up of members of a single discipline may have difficulty evaluating their work. That issue can put these researchers at a disadvantage, compared to candidates with more traditional backgrounds.

Interdisciplinary centers, institutes and programs are often less permanent structures than departments. Sometimes they’re devised as solutions to fill in the cracks between the work done in different departments or to address real-world problems. These centers are a kind of borderlands – they can attract scientists, especially established ones, who want to identify and pivot toward new research problems. But they’re not generally designed to support scientists’ careers long term.

Career challenges

Our 2024 study focused on biomedical research, which can benefit from an interdisciplinary approach because of the complexity of biological processes and human behavior.

A venn diagram of three circles
Interdisciplinary researchers work at the nexus of multiple academic subfields.
MirageC/Moment via Getty Images

To start, we wanted to understand whether researchers with interdisciplinary training had longer careers publishing their research than those without. The results were stark.

Interdisciplinary researchers stopped publishing much earlier than researchers who stuck to a single discipline. The most interdisciplinary researchers – those whose work draws the most on other disciplines beyond their primary field – had the shortest careers. Half of the most interdisciplinary researchers – the top 1% in terms of the interdisciplinarity of their work as graduate students – stopped publishing within eight years of graduation. Moderately interdisciplinary and single-discipline researchers kept publishing for more than 20 years.

Many interdisciplinary researchers left academia early in their career, by the point when most scholars transition into faculty positions and start to get promoted or receive tenure.

Many researchers who leave do important work in industry and other sectors. However, the high attrition rate of these researchers in biomedicine means that few senior scientists remain in academia to conduct interdisciplinary research or train future interdisciplinary researchers.

Researchers who started out as interdisciplinary tended to become more focused on one discipline early in their careers, as if recognizing that disciplinary work is the smoothest route to success.

However, we also found that over the 40-year period our study examined, biomedical research became more interdisciplinary overall. Ironically, single-discipline researchers, whose interdisciplinary work tends to be lower quality, drove that growth, becoming more interdisciplinary as their careers progressed.

But our study found that these researchers usually didn’t have specialized training in interdisciplinary research. They may have become more interdisciplinary through collaborations with researchers in other fields.

So, even though the overall level of interdisciplinarity in the field increased, trained interdisciplinary researchers left academia, and the single-discipline researchers without the same training were the ones conducting much of the interdisciplinary work.

Consequences for research

Our findings indicate another striking trend: Researchers entering the research community tended to be less interdisciplinary than the ones already in it.

Studies have shown that early career researchers often do the most innovative work. But at this formative career stage, they do not lend their talents to interdisciplinary work as frequently.

While many people in the academic community say they want to see more interdisciplinary research, the new, more discipline-focused scholars joining the system aren’t conducting this work.

Our analysis suggests that finding ways for universities, departments and funders to support early career interdisciplinary researchers could keep these scholars from leaving and increase the output of interdisciplinary work.

Many difficult societal problems will require research that cuts across the lines of established disciplines to solve. Right now, academia rewards scholars who work within disciplinary boundaries and climb the departmental career ladder.

To remedy this issue, universities and funding agencies could create better incentives for collaboration and research that addresses critical problems regardless of the discipline. These changes could create space for interdisciplinary researchers to thrive and become mentors for future generations of scientists.

The Conversation

Bruce Weinberg receives funding from the National Science Foundation, the National Institutes of Health, the Ewing Marion Kauffman and Alfred P. Sloan Foundations, as well as the National Bureau of Economic Research.

Enrico Berkes received funding from the National Science Foundation and the National Institutes of Health while a postdoctoral researcher at The Ohio State University.

Monica Marion has received funding from the National Science Foundation.

Staša Milojević received funding from the National Science Foundation and the Air Force Office of Scientific Research.

ref. Research institutions tout the value of scholarship that crosses disciplines – but academia pushes interdisciplinary researchers out – https://theconversation.com/research-institutions-tout-the-value-of-scholarship-that-crosses-disciplines-but-academia-pushes-interdisciplinary-researchers-out-254034

Nearly half of Detroit seniors spend at least 30% of their income on housing costs − even as real estate values fall

Source: The Conversation – USA – By Amanda Nothaft, Director of Data and Analysis, Poverty Solutions at the University of Michigan, University of Michigan

The high costs of maintaining a home can put Detroit seniors at risk. Nick Hagen/The Washington Post via Getty Images

For Detroit homeowners over 65 who overwhelmingly live on fixed incomes, unexpected costs – increases in grocery prices, rising health care premiums or an emergency repair – heighten their risk of financial instability and can even lead to them falling into poverty.

I am a policy researcher at Poverty Solutions at the University of Michigan. Our initiative uses action-based research, an approach that seeks to understand real-world problems and inform policy changes that could make life work better for people with low incomes. The center recently examined data from the 2023 American Community Survey to explore how low-income seniors in Detroit are affected by declining housing values and high housing costs compared to seniors across Michigan.

Federal, state and local programs to help seniors with these costs are already strained. As the population of older adults in metro Detroit continues to grow, demand for support services, such as caregiving and healthy meal programs, will likely increase.

Housing cost burdens are more acute for Detroit seniors

The poverty rate of senior-headed households in Detroit is nearly twice as high as the rate statewide.

Detroit seniors, both owners and renters, are more likely to be housing cost-burdened than Michigan seniors overall, with 45% paying more than 30% of their income on housing costs compared to 31% of seniors statewide. This is partially driven by lower median incomes in the city compared to the state.

Even when we focus on the seniors who would be considered the most financially stable, those who own their homes free and clear, the proportion burdened by housing costs is twice as high as the state: 32% versus 16%.

Detroit seniors pay more for property taxes and utilities

Lower incomes aren’t the only thing driving the higher housing cost burden. Detroit seniors pay more for all homeownership costs, including utilities – not only as a proportion of home values and income, but also in terms of real costs.

Detroiters face higher rates for auto insurance, and they pay more for utilities, compared to others in the state, adding to a situation where many residents, especially seniors on fixed incomes, struggle to make ends meet.

While the cost of living in urban areas is often higher compared to suburban and rural places, my analysis found that comparative costs for insurance, water, electricity and gas are lower in cities such as Milwaukee and Pittsburgh, which points to systemic issues that might be unique to Detroit.

Insurance and property taxes are also higher for seniors in Detroit compared to seniors across the state, especially relative to median home values. Detroit seniors pay the same or slightly more for these essentials despite living in homes that are worth less, based on the analysis.

The median house value for senior property owners in Detroit is $65,000, compared to $170,000 for seniors in Michigan.

High property taxes and insurance rates drive costs

Detroit lost over half a million residents between 1980 and 2020, causing an oversupply of single-family housing stock and a steady drop in home prices.

As residents left and businesses followed, the property tax base eroded. To generate the same revenue as cities with a richer tax base, Detroit levies property taxes at relatively high rates. Detroiters face a property tax rate close to 3%, significantly higher than the national average of 1.38%.

The housing market in Detroit has seen such large declines in property values that a disconnect has emerged. The replacement cost of a home, which is the actual expense required to reconstruct the dwelling, is often substantially higher than its current market value. This makes the cost of homeowner’s insurance disproportionately expensive relative to the market value of a home in Detroit.

A property’s condition and the condition of neighboring properties also raises the cost of homeowner’s insurance because insurance premiums are primarily influenced by the risk associated with insuring a property. Poor property and neighborhood conditions limit the availability of homeowner’s insurance, driving those who want homeowner’s insurance to purchase costly policies from insurers of last resort, or companies that provide coverage to people who cannot obtain it through other means due to high insurance risks.

The high cost drives many Detroit residents to forgo homeowner’s insurance. According to my analysis, almost 35% of Detroit seniors do not insure their homes, putting their main financial asset at risk.

Big utility bills

Utility bills in Detroit are higher compared to those statewide for two reasons: higher use and higher rates. The housing stock in Detroit is significantly older, with 88% of Detroit seniors living in houses built before 1960, compared to 34% of seniors in the rest of the state. These older homes use more energy because they often lack modern insulation and have single-paned windows, outdated appliances, older plumbing fixtures and poor seals around windows and doors.

Detroiters and others in Michigan served by DTE Energy, a utility provider, pay gas and electricity rates that are higher than others in the state. Detroiters also pay more for utilities due to a 5% “utility users tax” added to their gas and electricity bills. This surcharge isn’t new. It stems from legislation originally passed in the 1970s, and the funds collected flow to the Public Lighting Authority, which is responsible for improving and maintaining street lights in the city, and to the Detroit Police Department.

In the wake of Detroit’s bankruptcy filing in 2013, the Detroit Water and Sewerage Department carried out widespread shut-offs. From 2014 to 2020, the shut-offs affected as many as 141,000 Detroit residents, mostly those with low incomes. The crisis garnered national and international attention.

The initial crisis has passed, yet the cost of water continues to increase across the entire state, with those in the metro Detroit area served by the Great Lakes Water Authority seeing substantially higher rate increases than the state overall to cover deferred maintenance and infrastructure costs.

Costs are compounded by social isolation

Costs stemming from isolation and disability exacerbate the financial strain Detroit seniors already face.

Several factors contribute to older adults living alone, including increased life expectancy for women as well as children and family members moving farther away from each other. Older adults living alone are also more likely to be poorer than older adults who are a part of a larger household.

This issue is more pronounced in Detroit, where 54.7% of seniors live alone compared to the 43.2% statewide average. Living alone increases the risk of social isolation, which is linked to poorer health outcomes. Detroit seniors also have higher rates of disability than other seniors in the state of Michigan, which can lead to higher health care costs, decreased mobility and increased social isolation.

Less funding could create more hardship

Historically the demand for support outstrips the available resources, with only a small proportion of eligible households receiving energy assistance. And now, programs that help vulnerable seniors with the costs of utilities are at risk of funding cuts.

Detroit Water and Sewerage Department’s Lifeline Plan, launched in 2022, ran out of state and federal money in October 2025.

Meanwhile, the entire staff that administers the federal Low Income Home Energy Assistance Program, known as LIHEAP, was cut in April 2025. While the program is funded in the continuing resolution passed on Nov. 12, 2025, it is zeroed out in the president’s fiscal year 2026 proposed budget.

Even before funding uncertainties emerged, Detroit seniors who own their homes faced institutional barriers accessing property tax relief, putting many at risk of tax foreclosure. Additionally, Detroiters struggle to keep up with home repair costs, heightened by the needs of older homes and because the home repair assistance system is fragmented and difficult to access.

Without these programs, Detroit seniors will be left without an essential lifeline.

The Conversation

Amanda Nothaft does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. Nearly half of Detroit seniors spend at least 30% of their income on housing costs − even as real estate values fall – https://theconversation.com/nearly-half-of-detroit-seniors-spend-at-least-30-of-their-income-on-housing-costs-even-as-real-estate-values-fall-268075

Wars without clear purpose erode presidential legacies, and Trump risks political consequences with further military action in Venezuela

Source: The Conversation – USA – By Charles Walldorf, Professor of Politics and International Affairs, Wake Forest University

The body of U.S. Army Spc. Israel Candelaria Mejias is carried in a transfer case at Dover Air Force Base in Delaware after he was killed on April 5, 2009, near Baghdad. AFP Photo/Paul J. Richards via Getty Images

Despite public support in the U.S. for deposing Venezuelan leader Nicolás Maduro, President Donald Trump is unlikely to find that level of support for fighting an actual war in that country.

Even as Trump tries to work through Delcy Rodríguez, Maduro’s vice president and now the acting leader of the country, to manage Venezuela, there are echoes of President George W. Bush in Iraq with Trump saying that the United States will “run” Venezuela and “nurse it back to health” with Venezuelan oil wealth. None of that – which requires a lot of control by Washington and a major presence on the ground – can or will happen without a significant commitment of U.S. military forces, however, which Trump hasn’t ruled out.

“We’re not afraid of boots on the ground,” Trump said.

Yet U.S. citizens have been and remain deeply skeptical of military action in Venezuela. From Lyndon Johnson to George W. Bush, history shows that leaders often pay a high political price – and costs to their legacy, too – when wars they start or expand become unpopular.

As an expert on U.S. foreign policy and regime change wars, my research shows that every major U.S. war since 1900 – especially those that involved regime change – was buoyed at its outset by a big story with a grand purpose or objective. This helped galvanize national support to bear the costs of these wars.

During the Cold War, a story about the dangers of Soviet power to American democracy and the need to combat the spread of communism brought strong public support, at least initially, for wars in Korea and Vietnam, along with smaller operations in the Caribbean and Latin America.

In the 2000s and 2010s, the dominant narrative about preventing another Sept. 11 and quelling global terrorism generated strong initial public support for wars in Iraq – 70% in 2003 – and Afghanistan, 88% in 2001.

A big problem Trump now faces is that no similar story exists for Venezuela.

President Donald Trump said on Jan. 3, 2026, that the US is “not afraid of boots on the ground” in Venezuela.

What national interest?

The administration’s justifications for war cover a hodgepodge of reasons, such as stopping drugs that flow almost exclusively to Europe, not the U.S.; seizing oil fields that benefit U.S. corporations but not the wider public; and somehow curtailing China’s efforts to build roads and bridges in Latin America.

All these are unrelated to any story-driven sense of collective mission or purpose. Unlike Korea or Afghanistan at the start, Americans don’t know what war in Venezuela will bring them and whether it is worth the costs.

This lack of a holistic story or broad rationale shows up in the polls. In November, only 15% of Americans saw Venezuela as a national emergency. A plurality, 45%, opposed an overthrow of Maduro. After Maduro was removed in early January 2026, Americans’ opposition to force in Venezuela grew to 52%. No rally around the flag here.

Americans also worry about where things are heading in Venezuela, with 72% saying Trump has not clearly explained plans going forward. Few want the mantle of regime change, either. Nine in 10 say Venezuelans, not the United States, should choose their next government. And more than 60% oppose additional force against Venezuela or other Latin American countries.

Only 43% of Republicans want the United States to dominate the Western Hemisphere, indicating Trump’s foreign policy vision isn’t even popular in his own party.

Overall, these numbers stand in sharp contrast to past U.S. wars bolstered by big stories, where there was generally a deep, bipartisan consensus behind using force.

For the moment, 89% of Republicans support removing Maduro. But 87% of Democrats and 58% of independents are opposed.

Reflecting the national skepticism – and in a rebuke of Trump – the U.S. Senate advanced a measure to final vote requiring Trump to get congressional approval before taking further military action in Venezuela. Five Senate Republicans joined all Democratic senators in voting for the measure.

All told, the U.S. political system is flashing red when it comes to war in Venezuela.

Hubris can turn deadly

Research shows that U.S. regime change wars almost never go as planned. Yet, the hubris of U.S. leaders sometimes causes them to ignore this fact, which can result in deadly trouble. In Iraq, influential Vice President Dick Cheney told one interviewer, “We’ll be greeted as liberators.” We weren’t, and U.S. forces got bogged down in a bloody insurgency war.

Experts say the same trouble could come in Venezuela.

US soldiers sitting at a table with a tv behind them showing an image of Barack Obama.
U.S. Army soldiers watch a TV airing election coverage of Democratic presidential candidate Barack Obama at a base located along the Afghanistan-Pakistan border on Nov. 4, 2008.
David Furst/AFP via Getty Images

What might stop the United States from rolling into a deeper war that’s not in line with how the public views U.S. interests? My research shows that the answer lies with U.S. leaders taking steps to back away from owning what comes next in Venezuela.

This turns a lot on presidential rhetoric. When leaders make robust commitments to action, it often boxes them in politically later on to follow through, even if they don’t want to do so. Their words create what political scientists call “audience costs,” which are domestic political setbacks, or punishment, that leaders will face if they fail to follow through on what they promised to do.

Audience costs can even form in a case like Venezuela, because despite limited public support for force, the media along with proponents of war inside and outside government often pick up on a president’s words and produce a churning conversation. That conversation is visible now in the news cycle, with leading Republicans and other prominent voices calling for more robust action. It’s the “you broke it, you fix it” discussion.

This churn raises questions about the president’s credibility that sometimes makes leaders feel boxed in to act, even when public support is questionable.

As a presidential candidate in 2008, Barack Obama promised to devote greater attention and resources to the war in Afghanistan. When he got in office, Obama’s words came back to bite him. Political pressure generated by his campaign pledge made it almost impossible for Obama to avoid surging troops into Afghanistan at a much higher level than what he intended.

While presidents should always strive to keep the public informed of the direction policy is headed, research shows that leaders can avoid the trap of audience costs by remaining relatively vague and noncommittal, which the public now prefers, about future military actions.

On Venezuela, Trump has done some of this vague language work already by sidestepping specifics about when and if force will be used again, and by also downplaying talk of U.S.-led democracy promotion. If he stops talking about “running” Venezuela and adopts the more measured language used by advisers such as Secretary of State Marco Rubio, who says the goal is to “move (Venezuela) in a certain direction” but not run the country, Trump could take another step away from being boxed in to do more militarily.

Events on the ground in Venezuela might also factor into future U.S. policy. Obama would not have faced the political pressure for the surge that he did when coming to office if the Afghan war had been going in a more positive direction.

Venezuela is close to economic collapse, according to some experts, due to Caracas’ inability to reap the profits of selling oil abroad. If that happens, political chaos could follow and leave Trump, like Obama in Afghanistan, feeling lots of pressure to act militarily, especially if Trump is still saying he “runs” Venezuela.

Again, Americans don’t want that, which means taking steps, such as loosening the current oil embargo, to alleviate economic pain in Venezuela might make sense for Trump. Otherwise, if American troops are sent in by Trump and deaths mount, even a president deemed virtually untouchable by scandal and failure could find himself finally paying a political price for his decisions.

The Conversation

Charles Walldorf is affiliated with Defense Priorities.

ref. Wars without clear purpose erode presidential legacies, and Trump risks political consequences with further military action in Venezuela – https://theconversation.com/wars-without-clear-purpose-erode-presidential-legacies-and-trump-risks-political-consequences-with-further-military-action-in-venezuela-273199

Viruses aren’t all bad: In the ocean, some help fuel the food web – a new study shows how

Source: The Conversation – USA (2) – By Steven Wilhelm, Professor of Microbiology, University of Tennessee

A research ship sails in the Atlantic Ocean, where scientists are studying the roles of marine viruses. SW Wilhelm

Virus. The word evokes images of illness and fears of outbreaks. Yet, in the oceans, not all viruses are bad news.

Some play a helpful, even critical, role in sustaining marine life.

In a new study, we and an international team scientists examined the behavior of marine viruses in a large band of oxygen-rich water just under the surface of the Atlantic Ocean. What we discovered there – and its role in the food web – shows marine viruses in a new light.

Studying something so tiny

Viruses are incredibly small, typically no more than tens of nanometers in diameter, nearly a hundred times smaller than a bacterium and more than a thousand times smaller than the width of a strand of hair.

In fact, viruses are so small that they cannot be seen using conventional microscopes.

Four highly magnified images show a tiny round object, the virus. In two of the images, the tail is visible.
An electron microscope view shows examples of Prochlorococcus myoviruses. Images A and D show different viruses with their tails. In B and C, the tail is contracted. The black scale bar indicates a length of 100 nanometers.
MB Sullivan, et al., 2005, PLOS One, CC BY

Decades ago, scientists thought that marine viruses were neither abundant nor ecologically relevant, despite the clear relevance of viruses to humans, plants and animals.

Then, advances in the use of transmission electron microscopes in the late 1980s changed everything. Scientists were able to examine sea water at a very high magnification and saw tiny, circular objects containing DNA. These were viruses, and there were tens of millions of them per milliliter of water – tens of thousands of times greater than had been estimated in the past.

A theory for how viruses feed the marine world

Most marine viruses infect the cells of microorganisms – the bacteria and algae that serve as the base of the ocean food web and are responsible for about half the oxygen generated on the planet.

By the late 1990s, scientists realized that virus activity was likely shaping how carbon and nutrients cycled through ocean systems. We hypothesized, in what’s known as the viral shunt model, that the marine viruses break open the cells of microorganisms and release their carbon and nutrients into the water.

This process could increase the amount of nutrients reaching marine phytoplankton. Phytoplankton provide food for krill and fish, which in turn feed larger marine life across the oceans. That would mean viruses are essential to a food web that drives a vast global fisheries and aquaculture industry producing nearly 200 million metric tons of seafood.

Watching viruses in action

In the new study in the journal Nature Communications led by biologists Naomi Gilbert and Daniel Muratore, our international team demonstrated the viral shunt in action.

The team took samples from a meters-thick band of oxygen that spreads for hundreds of miles across the subtropical Atlantic Ocean. In this region, part of the Sargasso Sea, single-celled cyanobacteria known as Prochlorococcus dominate marine photosynthesis with nearly 50,000 to upwards of 100,000 cells in every milliliter of seawater. These Prochlorococcus can be infected by viruses.

What are Prochlorococcus? Science Magazine.

By sequencing community RNA – molecules that carry genetic instructions within cells – our team was able to look at what nearly all viruses and their hosts were trying to do at once.

We found that the rate of virus infection in this oxygen-rich band of the ocean is about four times higher than in other parts of the surrounding ocean, where cyanobacteria don’t reproduce as quickly. And we observed viruses causing massive infections in Prochlorococcus.

The viruses were attacking cells and spilling organic matter, which bacteria were taking up and using to fuel new growth. The bacteria respired away the carbon and released nitrogen as ammonium. And this nitrogen appears to have been stimulating photosynthesis and the growth of more Prochlorococcus cells, resulting in greater production that generated the ribbon of oxygen.

The viral infection was having an ecosystem-scale impact.

Scientists aboard a research vessel prepare a large device with many tubes for collecting samples once lowered into the ocean.
Scientists aboard a National Science Foundation research expedition in the open Atlantic in 2019 prepare equipment to collect water samples at different depths to analyze the activity of marine viruses.
SW Wilhelm

Understanding the microscopic world matters

Viruses can cause acute, chronic and catastrophic effects on human and animal health. But this new research, made possible by an open-ocean expedition supported by the National Science Foundation, adds to a growing range of studies that demonstrate that viruses are central players in how ecosystems function, including by playing a role in storing carbon in the deep oceans.

We are living on a changing planet. Monitoring and responding to changes in the environment require an understanding of the microbes and mechanisms that drive global processes.

This new study is a reminder of how important it is to explore the microscopic world further – including the life of viruses that shape the fate of microbes and how the Earth system works.

The Conversation

Steven Wilhelm’s work on this study was supported by The National Science Foundation, The National Institute of Environmental Health Science, the Simons Foundation and the Allen Family Philanthropies.

Joshua Weitz’s work on this study was supported by The National Science Foundation, the Simons Foundation, and the Blaise Pascal Chair of the Île-de-Paris Region.

ref. Viruses aren’t all bad: In the ocean, some help fuel the food web – a new study shows how – https://theconversation.com/viruses-arent-all-bad-in-the-ocean-some-help-fuel-the-food-web-a-new-study-shows-how-273088

Rural areas have darker skies but fewer resources for students interested in astronomy – telescopes in schools can help

Source: The Conversation – USA (2) – By Emma Marcucci, Executive Director of STARS, Smithsonian Astrophysical Observatory, Smithsonian Institution

Observing the night sky can get kids interested in astronomy and STEM careers. Jeremy Thomas/Unsplash

The night sky has long sparked wonder and curiosity. Early civilizations studied the stars and tracked celestial events, predicted eclipses and used their observations to construct calendars, develop maps and formulate religious rituals.

Scholars widely agree that astronomy is a gateway science – that it inspires a core human interest in science among people of all ages, from senior citizens to schoolchildren. Helping young people tap into their excitement about the night sky helps them build confidence and opens career pathways they may not have considered before.

Yet today the night sky is often hidden from view. Almost all Americans live under light-polluted skies, and only 1 in 5 people in North America can see the Milky Way. When people live in areas where the night sky is clearer, they tend to express a greater wonder about the universe. Altogether, this means communities with less light pollution have great potential to educate the next generation of scientists.

Rural communities have some of the darkest skies in the country, making them perfect for stargazing. Yet while students in rural areas are in the optimal physical environment to be inspired by the night sky, they are the most in need of science, technology, engineering and mathematics, or STEM, education resources to support their interests and build the confidence they need to pursue careers in science.

Stargazing, finding constellations and watching meteor showers as a kid inspired my own sense of awe around the vastness of space and possibilities in our universe. Now, I’m the executive director of the Smithsonian’s Scientists Taking Astronomy to Rural Schools, or STARS, a new program led by the Smithsonian Astrophysical Observatory, part of the Center for Astrophysics | Harvard & Smithsonian, that delivers telescopes and associated lesson plans to rural schools across the United States, free of charge. I’m working to share my excitement and wonder with students in rural areas.

The Sun, partially blocked by the Moon.
A solar eclipse, as viewed through a telescope.
STARS

Why hands-on STEM learning matters

Students need direct exposure to STEM careers and hands-on experiences that help them learn the skills they will need to pursue these careers on their own. Hands-on activities ground new knowledge in ways that lectures and reading often cannot. Experiential opportunities connect what may be distant or abstract concepts to clear, tangible, real-world skills. This experiential learning improves students’ understanding of astronomy content and increases their motivation to learn.

Telescopes are important tools for astronomy that scientists use all the time. When students use telescopes as part of their learning, they are experiencing real techniques that scientists use. Using a telescope brings the viewer closer to fantastic celestial objects – allowing them to see galaxies, nebulas, planets, the Moon and the Sun, with solar filter protection, more closely or in greater detail.

A full Moon, tinged orange from sunlight, during a lunar eclipse.
Telescopes help students view astronomical objects, like the Moon, up close.
STARS

There is nothing quite like seeing the soaring peaks and shadowed valleys of the Moon, or the distinct ring structure of Saturn, or endless other astronomical objects, through a telescope lens. This inspiration can motivate students to use their curiosity to explore the universe and see STEM careers as potential pathways.

Rural STEM education

The National Rural Education Association’s Why Rural Matters 2023 report estimates that there are 9.5 million students attending school in rural areas in the U.S., across more than 32,000 schools. This is more students than the student population of the 100 largest U.S. school districts combined.

While rural communities around the country all look different, they can face similar challenges: limited access to broadband internet, reduced state funding support and restricted geographical access to field trip opportunities, such as museums. Why Rural Matters found, on average, that 13.4% of rural households have a limited internet connection, and for some states this increases to 20%.

Each state distributes their education funding differently. The percentage allocated to rural schools varies from state to state, ranging from 5% to 50% of the total funding, which results in a wide range of money spent per student. Nonrural districts spend an average of US$500 more per student than rural districts. Looking state by state, however, this disparity climbs into the thousands of dollars.

Given their remote locations, rural areas host only 1 in 4 museums in the United States. Only 12% of children’s museums are in rural areas.

Educators may also consider STEM topics daunting. Many teachers do not feel adequately prepared or confident to introduce these topics to students. In other situations, there simply aren’t enough teachers to cover these topics. Shortages of STEM-focused teachers occur at some of the highest rates in rural districts, reducing rural students’ access to these subjects.

These reasons are why, through the STARS program, we give teachers access to a national community of practice that supports peer sharing and participation, alongside the telescope and science-aligned lesson plans. The lesson plans will be available online for anyone to use later this spring, whether or not they are part of the program.

STARS isn’t the only program connecting students with the night sky. Teachers, parents and students can also participate in national activities such as Observe the Moon Night and Globe at Night, and local activities, like their local amateur astronomy clubs.

A starry sky, silhouetted by trees.
Rural areas farther from cities tend to have darker skies, better for stargazing.
Ryan Hutton/Unsplash

Opportunities to observe the sky with telescopes lead to an improvement in learning outcomes and STEM identity, and rural schools are uniquely situated to introduce students to the night sky. With a little extra support, through community events and educational programs, these schools have the opportunity to inspire the next generation of scientists and engineers.

The Conversation

Emma Marcucci works for the Smithsonian Astrophysical Observatory, as Executive Director of the Smithsonian STARS program, which is supported through private gifts and donations.

ref. Rural areas have darker skies but fewer resources for students interested in astronomy – telescopes in schools can help – https://theconversation.com/rural-areas-have-darker-skies-but-fewer-resources-for-students-interested-in-astronomy-telescopes-in-schools-can-help-266848

Small businesses say they aren’t planning to hire many recent graduates for entry-level jobs – here’s why

Source: The Conversation – USA (2) – By Murugan Anandarajan, Professor of Decision Sciences and Management Information Systems, Drexel University

Small businesses often do not have the time or resources to onboard recent graduates with little or no experience. 020 Creative/iStock via Getty Images Plus

Small businesses are planning to hire fewer recent college graduates than they did in 2025, making it likely harder for this cohort to find entry-level jobs.

In our recent national survey, we found that small businesses are 30% more likely than larger employers to say they are not hiring recent college graduates in 2026. About 1 in 5 small-business employers said they do not plan to hire college graduates or expect to hire fewer than they did last year.

This would be the largest anticipated decrease in small businesses hiring new graduates in more than a decade.

Small businesses are generally those with fewer than 500 employees, based on standards from the U.S. Census Bureau and federal labor data.

This slowdown is happening nationwide and is affecting early-career hiring for people graduating from both college and graduate programs – and is more pronounced for people with graduate degrees.

Nearly 40% of small businesses also said they do not plan to hire, or are cutting back on hiring, recent grads who don’t have a master’s of business administration. Almost 60% said the same for people with other professional degrees.

National data shows the same trend. Only 56% of small businesses are hiring or trying to hire anyone at all, according to October 2025 findings by the National Federation of Independent Business, an advocacy organization representing small and independent businesses.

Job openings at small employers are at their lowest since 2020, when hiring dropped sharply during the early months of the COVID-19 pandemic.

Some small businesses may change their hiring plans later in the spring, but our survey reveals that they are approaching hiring cautiously. This gives new graduates or students getting their diplomas in a few months information on what they can expect in the job market for summer and fall 2026.

How small businesses tend to hire new employees

Our survey, which has been conducted annually at the LeBow Center for Career Readiness at Drexel University, collected data from 647 businesses across the country from August 2025 through November.

About two-thirds of them were small businesses, which reflects their distribution and proportion nationally.

Small businesses employ nearly half of private-sector workers. They also offer many of the first professional jobs that new graduates get to start their careers.

Many small employers in our survey said they want to hire early-career workers. But small-business owners and hiring managers often find that training new graduates takes more time and support than they can give, especially in fields like manufacturing and health care.

That’s why many small employers prefer to hire interns they know or cooperative education students who had previously worked for them while they were enrolled as students.

Larger employers are also being more careful about hiring, but they usually face fewer challenges. They often have structured onboarding, dedicated supervisors and formal training, so they can better support new employees. This is one reason why small businesses have seen a bigger slowdown in hiring than larger employers.

Then there are small businesses in cities that are open to hiring recent graduates but are struggling to find workers. In cities, housing costs are often rising faster than starting salaries, so graduates have to live farther from their jobs.

In the suburbs and rural areas, long or unreliable commutes make things worse. Since small businesses usually hire locally and cannot pay higher wages, these challenges make it harder for graduates to accept and keep entry-level jobs.

A cartoon image shows a man walking between two cliffs and heading toward an office chair with briefcase.
Recent graduates often land their first jobs with small businesses.
Alina Naumova/iStock via Getty Images Plus

Industry and regional patterns

Job prospects for recent college graduates depend on the industry. The 2026 survey shows that employers in health care, construction and finance plan to hire more graduates than other fields. In contrast, manufacturing and arts and entertainment expect to hire fewer new graduates.

Most new jobs are in health care and construction, but these fields usually do not hire many recent college graduates. Health care growth is focused on experienced clinical and support roles, while construction jobs are mostly in skilled trades that require prior training or apprenticeships instead of a four-year degree.

So, even in growing industries, there are still limited opportunities for people just starting their careers.

Even though small businesses are hiring less, there are still opportunities for recent graduates. It’s important to be intentional when preparing for the job market. Getting practical experience matters more than ever. Internships, co-ops, project work and short-term jobs help students show they are ready before getting a full-time position.

Employers often say that understanding how the workplace operates is just as important as having technical skills for people starting their careers.

We often remind students in our classes at LeBow College of Business that communication and professional skills matter more than they expect. Writing clear emails, being on time, asking thoughtful questions and responding well to feedback can make candidates stand out. Small employers value these skills because they need every team member to contribute right away.

Students should also prepare for in-person work. Almost 60% of small employers in our survey want full-time hires to work on-site five days a week. In smaller companies, graduates who can take on different tasks and adjust quickly are more likely to set themselves apart from other candidates.

Finally, local networking is still important. Most small employers hire mainly within their region, so building relationships and staying active in the community are key for early-career opportunities.

The Conversation

The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

ref. Small businesses say they aren’t planning to hire many recent graduates for entry-level jobs – here’s why – https://theconversation.com/small-businesses-say-they-arent-planning-to-hire-many-recent-graduates-for-entry-level-jobs-heres-why-272020

Colorado ranks among the highest states in the country for flu – an emergency room physician describes why the 2025-26 flu season is hitting hard

Source: The Conversation – USA (3) – By Jean Hoffman, Associate Professor of Emergency Medicine, University of Colorado Anschutz Medical Campus

Nationally, doctor’s visits for flu-like symptoms are at a 30-year high. Boston Globe/Getty Images

Colorado is in the midst of a record-breaking flu season. In the week ending Dec. 27, 2025, 831 people were hospitalized with influenza – the most since the state started tracking flu cases two decades ago. Hospitalizations eased the following week to 737 but still remain higher than prior years.

Colorado is among the top five states with the most flu activity in the country, with doctor’s visits for flu-like illness at a 30-year record high, according to the Centers for Disease Control and Prevention’s weekly influenza surveillance report.

I’m an emergency medicine and critical care physician at the University of Colorado. In my 18 years of practicing clinical medicine, this year is one of the worst I have seen. Our emergency department hit a record number of single-day total visits over the holidays, and visit volumes have stayed high. Flu is likely contributing to this trend.

While there is always a season where respiratory viruses hit hard, this year influenza is making patients miserable and wreaking havoc on both the state and national health care system.

How does this year’s ‘super flu’ differ from other flu seasons?

This season is especially rough because of the volume of people seeking emergency care. This flu came on fast and seems to be very contagious, and its symptoms are more severe than other recent years’ flu strains.

Flu tends to cause fever, body aches and maybe a cough. But this so-called super flu has also caused vomiting and diarrhea, which has made people feel much worse than isolated respiratory symptoms alone. When people are feeling worse, they seek emergency care, which is part of why our emergency department is seeing so many people.

In past flu seasons, which typically run from October through February, emergency rooms were full because they were facing multiple outbreaks, such as the 2022 “tripledemic” of COVID-19, flu and RSV.

But this 2025-26 flu season, we’re seeing high emergency department visits specifically from the flu. The first group of patients we’re seeing are healthy people who are feeling worse with this flu, which comes with nausea, vomiting and diarrhea, and come to the emergency department looking for symptomatic relief.

The second group are those with severe manifestations of the flu or who have underlying comorbidities such as asthma or heart disease that can be exacerbated by influenza. This is a population that may require oxygen, or they’re a transplant patient and they’re requiring hospitalization.

This double whammy of people feeling really miserable from their symptoms plus people with comorbidities experiencing complications is when you really see a strain on the health care system.

The CDC ranks Colorado’s flu activity among the highest in the U.S., along with Louisiana, New Jersey, New York and South Carolina.

Are any age groups being hit harder than others?

The U.S. is seeing the highest number of visits to emergency departments in children ages 5 to 17.

Kids generally seem to be having milder flu cases than adults, which is typical for some of these viruses. But there have been 17 pediatric deaths associated with influenza across the U.S., with eight in the week ending January 3. That number of deaths in children is not typical at this point in the season.

Young people in their 20s are feeling pretty bad from this year’s flu, but we’re not seeing a lot of complications or hospitalizations in this group across the U.S. and in emergency departments in Colorado.

We’re seeing a lot of people who have underlying conditions, such as asthma, as well as diabetes, obesity, heart disease and those who are immune-compromised. They get the flu, and then it leads to kind of a cascade, or a worsening of their underlying medical problems. This is different from what we saw with COVID-19, where healthy people got very, very sick from COVID-19 itself.

The older you get, the more likely you are to experience complications, such as needing oxygen, which typically requires hospitalization.

Are you still encouraging people to get the flu shot if they haven’t yet?

Yes, you should still consider getting your flu shot, especially if you have medical problems.

Getting an annual, updated flu shot helps with severity of diseases, even if it doesn’t provide total protection. Especially if you have underlying conditions, it’s important to do everything you can to decrease symptom severity, duration and risk of hospitalization.

An older woman in a red sweater is getting a shot in her arm by a man in a doctor's coat with blue gloves on.
Getting the flu shot reduces the risk of severe illness and hospitalization, especially for people who are older or have other medical conditions.
Genaro Molina/Getty Images

When should you consider going to an emergency room?

Anytime breathing becomes difficult, or you experience severe chest pain or headaches that are abnormal, that’s something that we want you to seek medical care for right away. And of course, if somebody’s worried about a symptom, we’re here 365 days a year, and we’re happy to help.

If you are feeling bad – such as a mild headache, body aches, fever, sometimes some cough and congestion, and as I mentioned with this flu, potentially vomiting and diarrhea – that is very normal.

If it’s flu, COVID-19 or RSV in a healthy, mildly symptomatic patient, it doesn’t really matter what they have, because there’s not a specific treatment. There’s not anything that we can do that’s going to make them better, other than “tincture of time,” meaning lots of rest.

If you have underlying medical problems, such as diabetes, lung problems or are immune-compromised, and you are experiencing severe symptoms, you should at the very least see your primary care doctor if not the emergency department.

Is it important to get tested for the sake of knowing what you have?

A lot of patients want to know what virus they have, but if you’re young and healthy, there’s not really a need for testing other than surveillance.

Colorado’s infectious disease trackers say wastewater surveillance is the No. 1 way to figure out what infectious diseases are in the community. We can’t get a comprehensive sample through hospitals and clinics, because there are so many people who are home, don’t get tested and do not seek health care.

A man wearing a mask and gloves shakes a large jug in a room with lab equipment.
In Colorado and other states, wastewater is tested for infectious pathogens, including influenza, COVID-19 and RSV. This testing indicates the prevalence of a virus in a given community.
Portland Press Herald/Getty Images

Right now, wastewater samples in Colorado are testing extraordinarily high for the flu and pretty low for RSV and COVID-19. Wastewater is a very reliable test because everybody produces wastewater.

In addition, it’s important for the overall health care system that laboratory testing be used judiciously. Testing does help us understand what’s in the community. But from a hospital and emergency department lens, the more tests we send to the lab that have to be run, the more testing services for other illnesses get backed up. It also adds a burden to nursing and other clinical staff, as well as costs for the patient and hospital.

But if a patient is sick with manageable symptoms from a virus, it’s the same standard advice: Stay at home, wash your hands and consider a mask if you have to go out in public.

The Conversation

Jean Hoffman does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. Colorado ranks among the highest states in the country for flu – an emergency room physician describes why the 2025-26 flu season is hitting hard – https://theconversation.com/colorado-ranks-among-the-highest-states-in-the-country-for-flu-an-emergency-room-physician-describes-why-the-2025-26-flu-season-is-hitting-hard-273069

From flammable neighborhoods to moral hazards, fire insurance maps capture early US cities and the landscape of discrimination

Source: The Conversation – USA (2) – By Jack Swab, Assistant Professor Department of Geography & Sustainability, University of Tennessee

1909 Sanborn map of Suffolk County in Boston, Mass. Library of Congress

Imagine a map that allows you to see what your neighborhood looked like a century ago in immense detail. What you’re thinking of is probably very much like the fire insurance maps produced from the 1860s to the 1970s for insurance companies to identify potential fire risks.

Often referred to as Sanborn maps, after the Sanborn Map Co. that produced them, fire insurance maps were created for every city in the United States with a population greater than 1,000 people. Over a century, more than 50,000 editions of these maps were produced, comprising over 700,000 map sheets – many of which have been scanned and are publicly accessible through the Library of Congress.

Close-up of a map of various buildings spread-out on white space
1917 Sanborn map of The Hill at the University of Tennessee, Knoxville.
Library of Congress

Genealogists, historic preservationists, historians and urban planners commonly use these maps to understand past urban landscapes. But as a critical cartographer interested in how maps shape how people understand the world, I see these maps differently.

Fire insurance maps supply more than just detailed insights into how neighborhoods looked decades ago. Needing to turn a profit, insurers sought to minimize the amount of risk they underwrote or charged higher premiums to account for risk. These maps provide important clues into how insurance companies understood how risk was distributed across cities, revealing costly biases.

Mapping fire risk

Before zoning and land-use planning, American cities frequently mixed industrial, commercial and residential buildings in the same block. Insurance agents used the immense detail of fire insurance maps to determine whether a property was too risky to underwrite, often weighing the demographics of the neighborhoods with the flammability of the buildings in the neighborhood.

Illustrated legend listing what different colors designate
Key to interpreting the Sanborn maps.
Library of Congress

For example, an Atlanta neighborhood called Lightning was a Black, working-class district composed of a mixture of rail yards, noxious industries and residences in 1911. The neighborhood was also an immense fire hazard. Atlanta’s primary trash incinerator stood less than 150 feet from two massive natural gas storage tanks, while two gas processing plants manufactured specialized fuels just feet from homes.

Underwriters would use information from fire insurance maps to understand the local landscape. In these maps, colors correspond to the building’s construction material: pink indicates brick, while yellow indicates wood. Lightning was primarily made from wood, placing the entire neighborhood at risk if a fire broke out.

Fire insurance maps and discrimination

At the same time, fire insurance maps also highlight the social landscape of the neighborhood.

Many buildings in the Lightning fire insurance map are labeled “F.B.,” which stands for “female boarding,” a euphemism for brothels. While brothels were not a fire risk themselves, this code indicated the alleged moral hazard of a neighborhood, or the likelihood that property owners would allow riskier activities to occur on their property that could cost insurers more.

Close-up of a map of various buildings spread-out on white space
1911 Sanborn map of the Lightning neighborhood of Atlanta, Ga. It’s now Mercedes-Benz Stadium, home to the Atlanta Falcons of the National Football League and the Atlanta United FC of Major League Soccer.
Library of Congress

From this one map, an underwriter could quickly see that Lightning was an extremely risky place to insure. Along with disinvestment from fire insurers, marginalized communities like Lightning also experienced other forms of systemic discrimination. Scholars have documented racial discrimination in car, life and health insurance underwriting.

Indeed, in the 1970s, much of Lightning was purchased under the threat of eminent domain – the legal process through which the government takes ownership of private land for public use – to construct the Georgia Dome, now the site of Mercedes-Benz Stadium.

Although fire insurance maps are no longer used in the insurance industry, they provide researchers one way of seeing how discrimination in fire insurance and urban planning manifested in the United States during the 20th century.

The Conversation

Jack Swab does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. From flammable neighborhoods to moral hazards, fire insurance maps capture early US cities and the landscape of discrimination – https://theconversation.com/from-flammable-neighborhoods-to-moral-hazards-fire-insurance-maps-capture-early-us-cities-and-the-landscape-of-discrimination-271271

Bilharziose en Europe : d’où vient cette maladie parasitaire et comment s’en protéger ?

Source: The Conversation – in French – By Christoph Grunau, Professeur des Universités, expert en épigénetique environnementale, Université de Perpignan Via Domitia

Les schistosomes, de petits vers parasites, sont à l’origine d’une maladie aux conséquences potentiellement graves : la schistosomiase ou bilharziose. Une simple baignade dans des eaux infestées par leurs larves peut suffire à être contaminé. Longtemps cantonnée à certains pays tropicaux, la maladie s’étend. Elle aborde désormais le sud de l’Europe : des cas ont été recensés en Corse, ces dernières années.


Plus de 240 millions de personnes dans le monde vivent avec un parasite dans le corps sans le savoir. Ces personnes sont infectées par des vers plats appartenant au genre Schistosoma, transmis par des escargots d’eau douce. Ils sont responsables d’une maladie appelée schistosomiase ou bilharziose, dont les complications peuvent être graves, allant jusqu’au cancer du foie ou de la vessie.

Si la grande majorité des personnes touchées vivent en Afrique, en Amérique latine ou en Asie, des foyers localisés ont également été récemment signalés en Europe, notamment dans le sud-est de la Corse.

Aujourd’hui, la lutte contre la bilharziose ne constitue donc plus seulement un enjeu de santé publique locale. Il s’agit d’un défi mondial, qui exige une veille épidémiologique accrue, une coopération internationale renforcée et des stratégies adaptées à une réalité environnementale en mutation.

Une même maladie, différentes manifestations.

La bilharziose est transmise par de petits escargots aquatiques vivant dans les eaux douces. Les larves de schistosomes les infectent, puis se multiplient dans leur organisme, avant d’être libérées dans les eaux environnantes.

Le cycle des schistosomes, responsables de la schistosomiase ou bilharziose.
DPDx, Centers for Disease Control and Prevention

Elles vont alors se mettre en quête de leur hôte final, un mammifère (rongeur, bétail, être humain…) immergé à proximité. Une fois à son contact, les larves percent sa peau et pénètrent dans son corps. Après un passage par le foie, elles se transforment en adultes, et s’installent dans les veines proches de l’intestin ou de la vessie.

Si, dans certains cas, les premiers stades de l’infection peuvent se traduire par une irritation de la peau ou de la fièvre, souvent la maladie reste silencieuse pendant des mois.

Les manifestations cliniques qui surviennent ensuite sont principalement liées aux centaines d’œufs produits chaque jour par les femelles. En effet, si une partie est éliminée en même temps que les matières fécales ou les urines (et peuvent donc à nouveau contaminer les eaux), certains restent piégés dans les tissus. Des lésions et des réactions inflammatoires se produisent, qui peuvent avoir de lourdes conséquences.

Cependant, la bilharziose ne se manifeste pas de la même façon partout. En effet, la forme de la maladie varie non seulement selon l’espèce de vers parasites impliquée, mais aussi selon l’espèce d’escargots qui les transmettent, ainsi qu’en fonction des saisons de transmission, propres à chaque région, ou encore des mesures de contrôle, très dépendantes des infrastructures locales.

Type de maladie Symptômes Espèce impliquée Répartition géographique
Schistosomiase intestinale – typiques: douleurs abdominales, diarrhée, et sang dans les selles;

– atteintes avancées: hépatomégalie (augmentation du volume du foie), parfois associée à une ascite (liquide péritonéal) et une hypertension de la veine porte qui augmente le risque d’hémorragie; une splénomégalie (augmentation du volume de la rate) peut aussi être observée. Risque de cancer du foie aux stades tardifs.

Schistosoma mansoni Afrique, Moyen-Orient, Caraïbes, Brésil, Venezuela et Suriname
Schistosoma japonicum Chine, Indonésie, Philippines
Schistosoma mekongi Plusieurs districts du Cambodge et de la République démocratique populaire lao
Schistosoma guineansis et S. intercalatum (espèce voisine) Zones des forêts tropicales humides en Afrique centrale
Schistosomiase urogénitale – typiques: hématurie (sang dans les urines);

– atteintes avancées: lésions rénales, fibrose de la vessie et de l’uretère, et risque de cancer de la vessie aux stades tardifs.

Schistosoma haematobium Afrique, Moyen-Orient, France (Corse)

Dans certains cas d’infection aiguë, des manifestations atypiques (paralysies) ont également été décrites. Chez les enfants, l’infection se traduit par une anémie (car les parasites se nourrissent des cellules sanguines de leur hôte) ainsi que par un retard de croissance.

Pour éviter la transmission de la maladie, outre les gestes individuels (voir encadré « Comment se protéger »), les programmes locaux de lutte contre les escargots et de sensibilisation communautaire sont essentiels, car ils permettent de rompre le cycle de transmission du parasite. Dans les zones endémiques, la participation aux campagnes de traitement collectif au praziquantel permet en outre d’éviter les formes chroniques.

Cette parasitose, bien que connue depuis longtemps, demeure malheureusement d’actualité. Chaque nouveau barrage ou projet d’irrigation, chaque communauté dépourvue d’assainissement créent les conditions pour une transmission renouvelée. Une situation encore aggravée par les modifications liées au changement climatique en cours, ou au développement de certaines pratiques, parmi lesquelles l’écotourisme, qui, en favorisant les voyages dans des zones rurales ou naturelles parfois peu surveillées sur le plan sanitaire, accroît le risque d’exposition à des eaux contaminées par les schistosomes.

Au sein de notre laboratoire, et en collaboration avec des centres de recherche en Europe, Amérique du Nord et Amérique du Sud ainsi qu’en Afrique de l’Ouest, nous travaillons à comprendre la dispersion des parasites et des mollusques vecteurs. Nous étudions aussi la possibilité d’améliorer la résistance des escargots contre le parasite, et nous explorons la possibilité de recourir à des modifications épigénétiques et génétiques pour rendre les parasites vulnérables.

Un parasite qui s’adapte aux activités humaines

Le cycle de la bilharziose repose sur trois éléments : le parasite, l’escargot, et l’eau. Dès que ces trois conditions sont réunies, la transmission est possible. Que ce soit dans les campagnes brésiliennes, le Nil en Égypte, les rizières asiatiques ou les rivières corses, la bilharziose s’adapte aux paysages humains.

En Afrique de l’Ouest, comme au Sénégal et au Bénin, les écosystèmes fluviaux et les températures élevées qui varient peu tout au long de l’année constituent des habitats idéaux pour les escargots appartenant aux espèces Biomphalaria et Bulinus, vecteurs des formes intestinale et urinaire de la maladie. Dans ces régions, la transmission est observée tout au long de l’année. Elle est plus importante au sein des populations ayant un contact intense avec l’eau, comme dans la ville fluviale de Ganvié (Bénin).

Photo de pêcheurs et habitants en pirogue dans la lagune de Ganvié, au Bénin. Ce type d’environnement, où l’eau douce est omniprésente et les contacts humains fréquents, constitue un terrain propice à la transmission de la bilharziose.
Pêcheurs et habitants en pirogue dans la lagune de Ganvié, au Bénin. Ce type d’environnement, où l’eau douce est omniprésente et les contacts humains fréquents, constitue un terrain propice à la transmission de la bilharziose.
Ronaldo Augusto, CC BY

Au Brésil, la forme intestinale prédomine. En général, les escargots vecteurs, principalement Biomphalaria glabrata, prolifèrent dans les réservoirs d’eau, les rivières et les lagunes. Les épidémies surviennent principalement dans les communautés rurales du Nord-Est et du Sud-Est, où l’accès à l’eau potable et à l’assainissement de base est souvent insuffisant.

Cependant, il est surprenant de constater que des épidémies peuvent apparaître dans les zones urbanisées, soit en raison de systèmes d’assainissement défaillants, soit parce que des rongeurs se trouvent à proximité de collections d’eau douce. Malgré le succès des programmes de lutte, cette complexité fait de la bilharziose une maladie dynamique, capable de s’adapter à différents scénarios selon la région du Brésil considérée.

Ces deux images prises dans l’État de Tocantins, au nord du Brésil, présentent deux scénarios contrastés de schistosomiase. Deux environnements endémiques distincts sont représentés : l’un, situé dans un parc naturel, où la transmission est principalement
Ces deux images prises dans l’État de Tocantins, au nord du Brésil, présentent deux scénarios contrastés de schistosomiase. Deux environnements endémiques distincts sont représentés : l’un, situé dans un parc naturel, où la transmission est principalement maintenue par la faune sauvage (photo de gauche). L’autre, en zone urbaine, se caractérise par la présence d’habitations et une dynamique de transmission dominée par les rejets de déjections humaines non traitées (photo de droite).
Ronaldo Augusto, CC BY

En Asie, la situation est encore plus complexe. En effet, l’espèce qui y sévit, Schistosoma japonicum, présente une capacité particulièrement marquée à contaminer de nombreux hôtes mammifères (elle infecte aussi bien les humains que les bovins et les rongeurs). Le risque d’infection est renforcé par les systèmes agricoles traditionnels, notamment la riziculture et l’élevage bovin, qui favorisent des contacts étroits et durables entre humains, animaux et milieux aquatiques (l’escargot vecteur, Oncomelania hupensis, vit dans les rizières et les zones humides). Cette situation complique fortement les efforts de contrôle. Par ailleurs, chaque inondation peut ouvrir de nouvelles zones de transmission.

Même dans les régions hors des zones tropicales, la bilharziose peut surprendre. C’est par exemple le cas en Corse, ou des touristes ont contracté la maladie après avoir nagé dans la rivière Cavu, entre 2013 et 2022.

Des analyses ont confirmé la présence sur l’île d’escargots Bulinus truncatus et du parasite S. haematobium, probablement introduit par des voyageurs en provenance de zones endémiques au Sénégal. Cet épisode a révélé la vulnérabilité de certains écosystèmes européens.

Une menace ancienne dans des paysages qui changent

Bien plus qu’une simple maladie tropicale, la schistosomiase est un indicateur des inégalités socio-économiques et de la manière dont nos environnements conditionnent notre santé. La comprendre, c’est aussi comprendre la façon dont s’entrelacent infrastructures, climat et comportements humains.

Mieux connaître cette maladie, et mettre au point des moyens de lutte efficace devient d’autant plus crucial que le changement climatique en cours favorise sa propagation. La hausse des températures et les modifications des régimes de pluie créent de nouveaux habitats propices aux escargots vecteurs. C’est aussi le cas de la pression sur les ressources en eau, qui conduit souvent à la création de barrages, de retenues artificielles et de systèmes d’irrigation. Autant d’aménagements générant des zones d’eau calme ou faiblement renouvelée, particulièrement favorables au développement desdits escargots.

Conséquence : de nouvelles zones de transmission pourraient apparaître là où le risque était jusqu’à présent considéré comme nul. Des modèles prédictifs suggèrent déjà que certaines régions du sud de l’Europe, notamment autour du Bassin méditerranéen, pourraient présenter les conditions écologiques nécessaires à l’établissement du cycle de transmission du parasite.

Il faut savoir que le parasite ne s’implante durablement dans une région que si l’hôte intermédiaire est présent et si les conditions climatiques sont favorables. Or plusieurs espèces d’escargots vecteurs, dont Planorbarius metidjensis et Bulinus truncatus, sont déjà présentes dans certaines régions d’Europe méridionale, ce qui explique un potentiel d’établissement localisé mais réel.

La réémergence de la bilharziose en Corse illustre comment cette maladie pourrait cesser d’être perçue uniquement comme une maladie tropicale négligée et commencer à être reconnue comme une infection émergente, y compris dans les pays du Nord.

The Conversation

Christoph Grunau a reçu des financements de l’ANR, de Wellcome Trust, de la Région Occitanie, et de l’UPVD.

Ronaldo Augusto a reçu des financements de l’ANR, de la Région Occitanie, et de l’UPVD.

ref. Bilharziose en Europe : d’où vient cette maladie parasitaire et comment s’en protéger ? – https://theconversation.com/bilharziose-en-europe-dou-vient-cette-maladie-parasitaire-et-comment-sen-proteger-260016

Additifs conservateurs : deux grandes études suggèrent des liens avec un risque accru de cancers et de diabète de type 2

Source: The Conversation – in French – By Mathilde Touvier, Directrice de l’Equipe de Recherche en Epidémiologie Nutritionnelle, U1153 Inserm,Inrae, Cnam, Université Sorbonne Paris Nord, Université Paris Cité, Université Paris Cité

Les additifs conservateurs sont présents dans de nombreux types d’aliments. Or, deux nouvelles études épidémiologiques d’ampleur suggèrent l’existence d’un lien entre leur consommation et un risque accru de cancer et de diabète de type 2. Anaïs Hasenböhler, qui conduit ces travaux, et Mathilde Touvier, qui dirige l’équipe de recherche en épidémiologie nutritionnelle (Cress-Eren, Inserm/Inrae/Cnam/Université Sorbonne Paris Nord/Université Paris Cité), ont répondu à nos questions.


The Conversation : En quoi ont consisté vos travaux sur les additifs conservateurs ?

Mathilde Touvier : Les deux études publiées en janvier s’inscrivent dans le cadre de notre projet de recherche sur les conséquences pour la santé résultant de la consommation d’additifs alimentaires. Depuis environ cinq ans, nous explorons cette voie afin de déterminer si elle peut expliquer les effets sur la santé des aliments industriels, notamment transformés ou ultratransformés.

Dans la lignée de nos précédents travaux sur les émulsifiants ou les édulcorants, nous nous sommes penchés sur la question des conservateurs, qui sont des additifs que l’on retrouve dans de nombreux produits : environ un produit sur cinq répertorié dans la base de données Open Food Facts en contient.

Pour cela, nous avons employé les données collectées dans le cadre de la cohorte NutriNet-Santé, dont l’originalité est de permettre, du fait de la finesse des données recueillies (marques des produits industriels consommés, dosages d’additifs dans certains aliments et boissons, questionnaires répétés sur plusieurs années…), de quantifier les expositions des participants à ces additifs, sur le long terme (le suivi depuis plus de quinze ans pour les premiers inclus). Durant les deux premières années du suivi, 99,7 % des participants ont été exposés à au moins un conservateur, d’où l’importance de s’intéresser à leur impact à long terme sur la santé.

Les analyses statistiques poussées que nous avons menées ont permis de mettre en évidence des liens entre le niveau de consommation de certaines de ces substances et le risque de survenue de certaines maladies chroniques.

Combien de conservateurs sont autorisés en France ? Quels sont ceux que vous avez étudiés ?

Anaïs Hasenböhler : Aujourd’hui, sur les quelque 330 additifs alimentaires autorisés en France et dans l’Union européenne, 80 ont des propriétés de conservateurs.

Parmi ces derniers, 58 se sont révélés être consommés par au moins un participant de l’étude NutriNet-Santé. L’ensemble de ces substances a été prise en compte pour calculer la somme totale d’additifs conservateurs consommés. Soulignons que dans ces travaux, 34,6 % des conservateurs consommés provenaient d’aliments ultratransformés. Nous avons également pu étudier davantage en détail 17 des conservateurs les plus consommés (c’est-à-dire consommés par au moins 10 % de la population), pour lesquels nous disposions de suffisamment de puissance statistique pour étudier le lien avec le risque de maladies chroniques.

Nos travaux révèlent que certains conservateurs étaient à la fois associés à une augmentation de l’incidence de cancer et de diabète de type 2. C’est le cas du sorbate de potassium (E202), du métabisulfite de potassium (E224), du nitrite de sodium (E250), de l’acide acétique (E260), de l’érythorbate de sodium (E316). Tandis que d’autres étaient plus spécifiquement associés à l’une ou l’autre de ces pathologies.

Concernant les cancers, qu’ont révélé vos résultats ?

M. T. : L’étude sur les cancers a porté sur les données de 105 260 participants à la cohorte NutriNet-Santé. Nous avons observé que les personnes qui consommaient davantage de certains conservateurs avaient un risque de cancer plus élevé, avec des associations spécifiques observées pour les cancers les plus fréquents dans la cohorte, à savoir ceux du sein et de la prostate.

La plupart des associations positives entre consommation de conservateurs et incidence plus élevée de cancers concernaient principalement les conservateurs non-antioxydants.

On peut citer les sulfites (trouvés surtout dans les boissons alcoolisées, responsables de 85,4 % des apports en sulfites chez les participants, mais aussi dans des sauces industrielles), les nitrites et nitrates (apportés principalement par les viandes transformées telles que les charcuteries), les sorbates (dont les sources sont plus variées : ils proviennent principalement de produits à base de fruits et légumes ou matières grasses et sauces, mais on en trouve aussi dans les desserts lactés, gâteaux et biscuits), et les acétates (largement utilisés dans les matières grasses et les sauces, telles que vinaigrettes ou condiments, ainsi que dans les viandes transformées, les préparations à base de produits laitiers, les plats préparés).

L’érythorbate de sodium, un additif antioxydant fréquemment ajouté aux viandes transformées (qui contribuaient à hauteur de 42,3 % des apports dans la cohorte) était également associé à une incidence plus élevée de cancer.

Lorsque nous comparions les plus forts consommateurs aux non consommateurs ou aux plus faiblement exposés, les pourcentages d’augmentation d’incidence étaient les suivants :

  • les sorbates, en particulier le sorbate de potassium, étaient associés à une augmentation de 14 % de l’incidence de cancer au global et à une augmentation de 26 % de celle de cancer du sein ;
  • les sulfites étaient associés à une augmentation de 12 % du risque global de cancer. En particulier, le métabisulfite de potassium était associé à une incidence accrue de 11 % de cancer au global et 20 % de cancer du sein ;
  • le nitrite de sodium était associé à une augmentation de 32 % du risque de cancer de la prostate ;
  • le nitrate de potassium était associé à une augmentation du risque de cancer au global de 13 % et de cancer du sein de 22 % ;
  • les acétates étaient associés à une augmentation du risque de cancer au global de 15 % et de cancer du sein de 25 %. Spécifiquement, l’acide acétique était associé à une augmentation de 12 % du risque de cancer en général ;
  • les érythorbates totaux et l’érythorbate de sodium en particulier étaient associés à une incidence plus élevée de cancer au global (12 %) et du cancer du sein (21 %).

La puissance statistique était limitée pour les autres localisations de cancer, qui sont moins fréquemment représentés en population générale et donc également dans la cohorte. Un mode de vie globalement plus sain explique aussi l’incidence plus faible de certains cancers dans l’étude, ce qui a pu empêcher de mettre en évidence pour le moment les associations connues entre nitrites et cancer colorectal, par exemple.

Qu’avez-vous découvert concernant le risque de diabète de type 2 ?

M. T. : L’étude sur le diabète de type 2 a porté sur les données de 108 723 participants de la cohorte NutriNet-Santé. Nos travaux ont permis d’observer une association positive significative entre une exposition plus élevée aux additifs alimentaires conservateurs et une incidence plus forte de diabète de type 2 : les plus gros consommateurs de conservateurs avaient un risque supérieur estimé à 47 % de développer la maladie, comparés aux consommateurs qui en absorbaient le moins.

Sur les 17 conservateurs étudiés individuellement, une consommation plus élevée de 12 d’entre eux était associée à un risque accru de diabète de type 2 : des conservateurs alimentaires non antioxydants largement utilisés – nitrite de sodium (E250, incidence supérieure de 50 % chez les plus forts, comparés à de plus faibles consommateurs), métabisulfite de potassium (E224, 29 %), sorbate de potassium (E202, 115 %), acide acétique (E260, 31 %), acétates de sodium (E262, 23 %) et propionate de calcium (E282, 44 %) – et des additifs antioxydants : ascorbate de sodium (E301, 41 %), alpha-tocophérol (E307, 30 %), érythorbate de sodium (E316, 43 %), acide citrique (E330, 29 %), acide phosphorique (E338, 39 %) et extraits de romarin (E392, 20 %).

Que faut-il retenir de ces résultats ?

M. T. : Ces deux études sont les premières au monde à quantifier les expositions à un large spectre de conservateurs et à étudier leurs liens avec le risque de cancers et de diabète.

S’il est un point qui nous a interpellés, c’est la proportion de conservateurs dont la consommation s’est révélée associée à une incidence plus élevée de ces pathologies : sur les 17 que nous avons testés spécifiquement, 6 étaient associés à une incidence accrue de cancer, et 12 étaient associés au risque de diabète de type 2.

A. H. : Ces résultats épidémiologiques sont cohérents avec de précédents travaux expérimentaux qui consistent à exposer des cultures de cellules ou des modèles animaux à des conservateurs. Dans le cas du diabète de type 2, de telles études avaient par exemple suggéré que certains conservateurs pourraient altérer la signalisation de l’insuline. Parmi les autres pistes d’explication figurent les perturbations du microbiote intestinal, mais aussi des mécanismes d’oxydation, de stress oxydant ou d’inflammation qui pourraient être impliqués dans l’apparition de cancers.

Y a-t-il des limites à cette étude ?

M. T. : Il est important de rester prudent concernant les pourcentages d’augmentation d’incidence observés quand on compare les consommateurs les plus fortement exposés aux moins fortement exposés.

En effet, ces chiffres ne s’appuient que sur une seule étude, basée sur la cohorte NutriNet-Santé. Même si celle-ci est fondée sur une très large population d’étude, avec des données fines d’exposition et un contrôle poussé des principaux facteurs de risque (tabagisme, consommation d’alcool, de sucre, sel, fibres, antécédents familiaux de maladies ou encore activité physique), il va falloir les confirmer par d’autres travaux (études épidémiologiques sur d’autres cohortes, puis méta-analyses…).

Cependant, les associations que nous avons mises en évidence sont statistiquement significatives et concordent, comme on l’a souligné, avec les travaux expérimentaux qui ont déjà été menés.

Quelles mesures prendre pour mieux protéger la santé des consommateurs ?

M. T. : Contrairement aux autres types d’additifs alimentaires (émulsifiants, édulcorants, colorants…), l’intérêt des conservateurs va au-delà du cosmétique et de l’organoleptique.

Ils sont employés pour protéger les aliments contre des altérations potentiellement délétères pour la santé des consommateurs, qu’il s’agisse de modifications chimiques (oxydations) ou de contaminations par des microorganismes.

Le ratio bénéfice-risque de ces substances devra donc être pris en compte dans les futures réévaluations de leur sécurité. Il s’agira de déterminer, au cas par cas, si les conservateurs sont réellement indispensables ou s’ils sont utilisés pour des intérêts, notamment économiques, qui dépassent la seule sécurité alimentaire (garder plus longtemps les produits dans les rayons pour faire des économies, par exemple), s’il existe des alternatives, etc.

Au final, nous espérons que nos travaux permettront de nourrir ces futures ré-évaluations (par l’EFSA, la FDA, etc.), et de faire évoluer la réglementation pour mieux protéger les consommateurs, en abaissant si besoin les doses limites autorisées ou en interdisant certaines substances.

Dans nos perspectives de recherche à court terme, nous poursuivons également des travaux sur les liens entre les additifs conservateurs et le risque de maladies cardiovasculaires et d’hypertension. Nous explorons aussi l’impact des mélanges d’additifs sur le risque de maladies chroniques ainsi que celui de contaminants issus des procédés de transformation et des emballages.

Nous recherchons les mécanismes sous-jacents en dosant des biomarqueurs sanguins d’inflammation, de stress oxydant, de perturbation du métabolisme et en étudiant les microbiotes des participants, en lien avec leurs profils d’expositions aux additifs et aux aliments ultratransformés et leurs contaminants.

Nos partenaires toxicologues et physiologistes complètent ces travaux par des approches expérimentales. Enfin, nous travaillons également sur l’évolution du logo Nutri-Score pour permettre d’intégrer ces nouvelles dimensions en plus du profil nutritionnel, avec par exemple un cadre noir pour signaler si l’aliment est « ultratransformé ».

D’une façon plus générale, ces résultats plaident pour l’application des recommandations du Programme national nutrition santé : privilégier les aliments pas ou peu transformés et limiter les additifs superflus…

The Conversation

Mathilde Touvier a reçu des financements d’organismes publics ou associatifs à but non lucratif (ERC, ANR, INCa, etc.).

Anaïs Hasenböhler a reçu des financements (PhD grant) de Université Sorbonne Paris Nord.
Ces travaux ont été financés par des fonds publics ou associatifs à but non lucratif (ERC, INCa, Ministère de la Santé, …)

ref. Additifs conservateurs : deux grandes études suggèrent des liens avec un risque accru de cancers et de diabète de type 2 – https://theconversation.com/additifs-conservateurs-deux-grandes-etudes-suggerent-des-liens-avec-un-risque-accru-de-cancers-et-de-diabete-de-type-2-273297