One of the most visible ways that Canada responded to President Donald Trump’s tariffs was by sharply restricting U.S. alcohol sales. AP Photo/Jill Colvin
Almost a year and a half after President Donald Trump began slapping tariffs on nearly all U.S. trading partners, Canada’s pushback has reordered the economic relationship between Ottawa and Washington.
But the example of one sector in particular, U.S. alcohol, shows how quickly access to an important market can disappear – and how difficult it can be to regain.
From 2022 through 2024, Canada accounted for roughly 35% of U.S. wine exports, more than 15% of U.S. beer exports and as much as 13% of U.S. distilled spirits exports. Within just one year of Trump returning to office, Canada’s imports of U.S. alcohol cumulatively have plunged over 70%, thanks to a mix of both tariff and nontariff retaliatory measures.
It’s a sharp reversal from Canada’s traditional role as a top foreign destination for American beer, wine and spirits. That relationship reflected both long‑standing consumer preferences as well as geographic proximity and largely tariff‑free access through agreements like the North American Free Trade Agreement and its successor, the United States-Mexico-Canada Agreement.
As an agricultural economist working on trade issues related to alcohol, I see Canada’s alcohol sector as a textbook example of how market access for politically exposed goods can quickly unravel. And for American beer, wine and spirits producers – and for the farmers who grow the barley, grapes and corn that go into these products – the recent experience highlights how trade disputes often hit food products hardest. If a trade ban becomes entrenched, it opens a way for consumers to develop a taste for domestic as well as other foreign alternatives.
President Donald Trump’s tariffs and talk of Canada as the 51st U.S. state have sparked a sustained backlash by Canadians. These protesters gathered near the Peace Bridge border crossing in Buffalo, N.Y., on April 2, 2025. AP Photo/Adrian Kraus
The Trump tariff shock
Before Trump’s tariffs and talk of Canada as the 51st U.S. state, U.S. alcohol occupied substantial shelf space in major alcohol-consuming provinces such as Ontario, British Columbia and Québec. In 2024, these exports to Canada constituted more than 20% of Canada’s alcohol imports, totaling US$744 million. For most U.S. producers, Canada served not only as a key export destination but as a stable and relatively low‑risk entry point into international markets.
That changed in February 2025, when Trump, citing a national security emergency, imposed 25% tariffs on Canada and Mexico. Those tariffs – which were overturned by the Supreme Court in February 2026 – marked the first time that law was used to authorize broad tariffs.
Canada responded by slapping retaliatory tariffs of 25% on roughly $30 billion of U.S. goods and signaling it would significantly expand countermeasures if tensions persisted. It also enacted nontariff countermeasures, most notably by letting provincial liquor authorities remove U.S. beer, wine and spirits from store shelves. These tools, which fall within Canada’s system of shared federal and provincial powers, sharply restricted market access for American producers.
Immediately after Trump’s announcement, eight of Canada’s 10 provinces imposed partial or full bans on U.S. alcohol imports by instructing their liquor boards to stop importing and selling U.S. alcohol altogether. In many cases, American products were physically removed from store shelves and online platforms – sometimes with instructions to target imports from U.S. “red” states that had supported Trump.
U.S. wine exports were hit hardest, plunging from $460 million to just $103 million, while distilled spirits fell from $238 million to $89 million and beer exports from $47 million to $17 million. Collectively, these declines slashed total U.S. alcohol exports to Canada from $744 million to $208 million, wiping out $536 million in trade.
The spat quickly became testy. The alcohol boycott is one of the reasons Trump and White House officials have called Canada “mean and nasty to deal with,” in the words of U.S. Ambassador to Canada Pete Hoekstra.
The trade war’s latest turn
Those provincial restrictions remained in place even after the two countries reached a partial deal exempting about half of USMCA‑compliant goods from ongoing tariffs in summer 2025, leading Canada to scale back some retaliatory levies. However, the de facto trade bans on U.S. alcohol remain in place.
Alcohol resurfaced again recently as a flash point, when the top U.S. trade official, Jamieson Greer, said in April 2026 that existing U.S. levies on Canadian industrial goods would stay in place and might even be toughened until Canada walked back its alcohol restrictions. That threat a drew sharp retort from Canadian Prime Minister Mark Carney.
Meanwhile, the trade dispute hasn’t prompted Canadians to drink less alcohol overall. Instead, their consumption has largely shifted to other countries, especially for wine. United Nations trade data shows that in 2024, American wine accounted for 21% of all imported wine in Canada before dropping to only 5% in 2025. That year, imports from major wine exporting countries not only increased but roughly offset the decline in imports from the U.S. For distilled spirits, the U.S. slipped from 24% in 2024 to only 10% in 2025, while beer has dropped from 13% to 5%. At the same time, Canadian imports of beer, wine, and spirits from other countries increased by 9%, 15%, and 7%, respectively.
“What’s different this time is that people aren’t just swapping one bottle, they’re rethinking the whole bar,” said Craig Peters, CEO of Canada’s Barnburner Whiskey, in an interview with the online magazine VinePair. “Traditionally, those rail spots were locked up by big U.S. brands for decades. Now, we’re seeing bars, especially independents, completely reset and go Canadian across the board.”
Andrew Muhammad has received funding from the U.S. Department of Agriculture and the Southern U.S. Trade Association to address issues related to U.S. distilled spirits trade.
I have been a dog lover ever since I was a kid and have spent years learning about the temperaments and histories of different dog breeds, as well as famous dogs and their adventures. I have attended a variety of dog shows to meet various breeds and talk with their owners, and I’ve also lived with several dogs – including a dachshund, otterhound, German shepherd, Indian spitz and Labrador retriever – over the course of my life.
Beyond my canine concerns, I’m a professor of management who loves teaching courses and conducting research on leadership. So, it was a no-brainer for me to combine my two interests to write a book, “Learning Leadership from Dogs.” Various dog breeds embody distinct traits and behaviors that we humans can emulate to become better leaders.
Here are five qualities dogs model that any leader, at work or in life, can learn from.
The author’s own otterhound Fiona was always up for a good time. Aditya Simha
Joie de vivre
Happy-go-lucky hounds have an abundance of joie de vivre, a French phrase that refers to a cheerful and exuberant enjoyment of life. My own otterhound, Fiona, amply embodied this trait. A simple walk in the woods or hike on the beach was all she ever wanted.
This kind of optimism and cheerfulness can make leaders more empathetic and pleasant to work with, partly because psychology research finds that positive moods increase helping, generosity and interpersonal understanding. Those are key ingredients of empathy.
While there are many dog breeds that embody courage, I want to single out the Dutch shepherd. Smaller than the German shepherd and the Belgian Malinois, the Dutch shepherd is used in police and military work because of its athleticism, trainability and strong work ethic. Just like how Dutch shepherds run toward danger to protect others, courageous leaders take risks for their values and to support their team.
Intelligence
Leaders must not only know about their domain, they also need to be able to understand which of their followers needs to be treated or led differently. Both emotional and cognitive intelligence are essential for effective leadership and have positive consequences for their followers’ attitudes and performance.
I point to the border collie as a dog that exemplifies both forms of intelligence. The border collie not only knows how to herd sheep, but also which sheep to herd with patience and which sheep need a bit more sharpness.
This intelligence is something that needs to be guided and channeled. Border collies left without enough work or stimulation are famous for finding their own “jobs,” such as herding the human children, chasing shadows or inventing new mischief around the house.
Without proper direction, even brilliance can become counterproductive – another lesson leaders can keep in mind when managing their own flocks.
Kindness
Kindness is one quality that is sadly not given the amount of attention it merits in the world of management, even though it can shape whether followers feel respected, trusted and willing to contribute.
Displaying kindness is a canine specialty. The dog breed that comes to mind for me here is the Newfoundland. First bred in Canada and known as a fine water rescue dog, these gentle giants are supremely kind to everyone and display a benevolent, protective nature.
Leaders similarly need to be kind to their followers, even if a team member has failed at a task. A kind response does not mean ignoring mistakes; it means correcting them in a way that preserves dignity, making followers more likely to learn, speak up and try again. Together those patterns facilitate work environments that promote what researchers call psychological safety: a shared belief that people can ask questions, admit mistakes and raise concerns without fear of embarrassment, rejection or punishment.
Resilience
Resilience is not just toughness; it is the ability to recover from setbacks, adapt under pressure and keep moving forward when things don’t go as planned. Leaders rely on it during crises, failed projects, public criticism or periods of organizational change, all moments when uncertainty is high and confidence can falter.
Any leader can look to the Rhodesian ridgeback as a resilience role model. This breed hails from South Africa and was originally used to assist in lion hunting – an activity fraught with peril and with high prospects of failure. Rhodesian ridgebacks are dauntless dogs, always ready to try another dangerous hunt even in the wake of repeated failures.
Like these dogs, leaders often must confront perilous tasks with a high likelihood of failure, and they must be ready to bounce forward so they can eventually seize success. Without resilience, leaders may panic, withdraw or become overly reactive, especially during a crisis. When that happens, uncertainty spreads, confidence erodes and teams are less likely to stay focused or move forward effectively.
Dogs are the most popular choice of pet in the United States and worldwide. You probably don’t need to look far to find some furry friends who can inspire you with their admirable characteristics. Dogs may never author a leadership book, but they live out leadership lessons in courage, kindness and joy every day.
Aditya Simha 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.
So why are so few people physically active when the benefits are widely known?
As a physical therapist and rehabilitation scientist who studies how to boost movement for people living with chronic conditions and physical disabilities, I spend a lot of time thinking about that question.
The short answer is that understanding the importance of exercise usually doesn’t translate into exercising. Making it a part of your lifestyle requires believing you can do it and knowing you can do it.
Exercise is a lifestyle choice that helps reduce the likelihood of developing a chronic illness. But the good news is that if you’re one of the 194 million Americans already living with one or more chronic illnesses, beginning or maintaining an exercise routine can slow the progression, reduce symptoms and improve health outcomes.
An array of health benefits
The list of benefits from movement is long. Here are just a few examples:
While some movement is better than none, the Centers for Disease Control and Prevention offer research-based guidelines for the type and frequency of activities to engage in weekly for long-term health benefits.
The CDC encourages all adults, including those with chronic health conditions or disabilities, to aim for at least 150 minutes of moderate intensity aerobic activity, such as walking, jogging or swimming. Adults should also do muscle-strengthening activities two or more days per week, which could include weightlifting and body weight exercises.
Older adults should add balance activities, such as tai chi or yoga, to help prevent falls by challenging the body’s balance systems.
If you’re not achieving these recommended weekly physical activity guidelines, you’re not alone. Only half of Americans hit the aerobic target, and just 1 in 4 meet the full CDC guidelines.
This gap represents a health crisis that, if addressed, could save lives. A 2024 large-scale review showed that people who engage in regular physical activity in adulthood may reduce the risk of early death by 30% to 40% from all causes, most specifically from cardiovascular disease and cancer.
The study also showed that beginning exercise at any time in adulthood can improve survival benefits.
Instead, shifting your beliefs about the barriers preventing you from exercise might actually be the key to get you moving more.
In 1977, a psychologist named Albert Bandura proposed that the ability to perform a task even when it’s difficult – a concept called self-efficacy – is the most important personal characteristic that drives healthy changes in behavior.
Half a century later, self-efficacy is still considered one of the most crucial personal factors for behavioral change when it comes to long-term physical activity. Researchers who develop and test exercise interventions, including me, evaluate novel tools and programs that are built to boost self-efficacy.
Someone with high self-efficacy might say that they can get back to their exercise routine even if they miss a day. Or they might find a way to still exercise when they’re busy or tired. Someone with lower self-efficacy might be thrown off their routine if presented with the same obstacles.
But how do you build this crucial trait and get moving more? A meta-analysis found that despite its importance, there is not one magic way to boost self-efficacy.
That’s because people’s behavior is more complicated than individual factors alone. People and groups have varying needs and contexts that require tailored approaches.
Self-efficacy may be affected by multiple factors, but people can still apply techniques to boost their ability to start and stay with an exercise routine.
Make it manageable. It may seem intuitive to set personal goals, but many of us aim too high and end up discouraged. Goals focused on weight loss, heart health or muscle strength are fine, but they can take a long time to achieve. Long-range goals don’t tend to be motivating in the difficult moments – like when you want to hit snooze but promised yourself that you were going to take a long walk before work.
Instead, try short-term goal-setting – such as aiming to get a set number of lunchtime walks in during the workweek. This will move you toward your long-term goals, while making it easier to see and feel progress.
In 2026, the American College of Sports Medicine refreshed its guidance on strength training, which represents synthesized findings from 137 systematic reviews and the first update since 2009. The biggest recommendation difference? Consistency matters more than specificity of strength programs. What that means is that doing any strength training has health benefits as long as it is the kind you will keep doing.
Make it add up. The CDC’s recommended 150 minutes of aerobic activity is meant to be spread throughout the week – not done all at once. Research shows that small bursts of activity still have significant impacts on your overall health, and you’re much more likely to stick with them.
Only have 15 minutes while your kid is asleep? Have a short exercise video or app cued up for nap time. Waiting for your next Zoom meeting to start? Climb your stairs once or twice. Microwaving your lunch? Hold on to the counter and lift and lower your heels until the timer goes off. Every little bit matters to your mind and body.
Make it meaningful. Prioritize doing things you enjoy. The gym is not for everyone, and luckily this style of structured exercise is just one of many options for physical activity. Go bird-watching, join a gardening group, binge watch your favorite show on the treadmill. Any activity you do that uses energy is like dropping a coin into your weekly physical activity bank.
Make it more fun. Choose to be around people who are already exercising – and who encourage you to do it, too. Research shows that people who are sedentary will increase their physical activity by socializing with someone who is active.
But the thing to remember is that even small improvements can have big impacts. It is consistent practice – not perfection – that is key to reaping all the benefits physical activity has to offer.
Laura Baehr receives funding from the Department of Defense, the Arthritis Foundation, and the Clinician-Scientists Transdisciplinary Aging Research Coordinating Center (a National Institutes of Health National Institute on Aging funded center).
If you follow the Trump administration’s social media posts, you might spot its new mascot: a cartoon lump of coal with big eyes and babylike features. “Coalie” sparked a backlash almost as soon as Interior Secretary Doug Burgum debuted it for the Office of Surface Mining and Reclamation Enforcement in early 2026.
As a scholar of American literature and culture, I write about media portrayals of coal, beginning in the 19th century with its rise to become the leading fuel in the United States. Coal use grew until the early 2000s, when other sources became cheaper and its health and environmental damage became unacceptable to more of the public.
While “Coalie” might be new, the logic behind it is not. For centuries, coal’s promoters have worked hard to show coal as harmless – as well as “clean” and “beautiful,” to use President Donald Trump’s words.
‘An agreeable heat’
Humans living with the effects of burning coal have disliked it for as long as they have burned it.
In 1578, Queen Elizabeth complained that she was “greatly grieved and annoyed with [its] taste and smoke” in the air. In 1661, John Evelyne’s treatise Fumifugium outlined negative health effects of breathing coal smoke.
English settlers were drawn to North America in part because of the continent’s abundant supply of timber, a substitute for coal that deforestation had made prohibitively expensive in England.
In addition to its lower price, anthracite coal grew desirable because of its high carbon, low-sulfur content, which produced less visible smoke when it was burned. An enthusiastic 1815 letter to the editor of the American Daily Advertiser captured increasingly common attitudes toward anthracite as “affor[ding] a very regular and agreeable heat.”
‘A healthful home’
The spread of anthracite also shored up tolerance for smokier but cheaper bituminous coal.
To help people, housekeeping manuals aimed at the fossil fuel’s mostly female users tried to invent workarounds for its smoke. In 1869, Harriet Beecher Stowe, best known as the author of “Uncle Tom’s Cabin,” and her sister Catharine Beecher wrote one of many 19th-century articles to acknowledge the “evils” of coal smoke, while outlining “modes of making a healthful home,” in the housekeeping manual American Woman’s Home.
Consumers provided temporary solutions for maintaining indoor air quality while burning coal by sending in suggestions that were published in housekeeping manuals, magazines and newspapers.
An 1892 advertisement in the Rocky Mountain News promoted a brand of coal stoves as ‘the best, handsomest and most economical.’ Nineteenth Century Newspapers
At the same time, as the century progressed, coal and coal-stove companies began to suggest that burning coal was healthy, that it could improve indoor air as well as domestic aesthetics. One 1892 newspaper advertisement claimed that stoves were “necessary to heat, cheer, and beautify the home and preserve its health.”
To keep the children clean and bright …
In the 20th century, marketers churned out more colorful claims about the benefits of coal: One magazine advertisement showed a mother and child pointing at the crackling stove aflame with the company’s coal, saying it “cannot be excelled in purity, cleanliness, and free-burning qualities.”
Similarly, the Lackawanna Railroad Company came up with the classy, often rhyming, character of Phoebe Snow. In one ad, she points to the importance of comfort, suggesting that not only could anthracite fuel faster travel, but it could also make your travel – and your life – more comfortable.
Coal marketing often used children to suggest safety and reach parents. Another iteration of the Phoebe Snow series promised that anthracite-powered railway travel could keep children “clean and bright.”
A 1930s advertisement went so far as to position a piece of anthracite coal next to a child in a bathtub, a visual proximity implying that coal was as good as soap.
In fact, soap made of “coal tar” – a liquid byproduct of producing coke, a fuel made from bituminous coal used in industrial blast furnaces – did (and does) exist. The British company Wright’s, also popular in the U.S., generated a slew of advertisements praising its soap as having antiseptic properties for children.
Wright’s Coal Tar Soap used a sleeping child dressed in white and sleeping on white sheets to advertise its ‘nursery soap,’ which it claimed protected children from infection, in 1922. Wikimedia Commons
Each of these advertisements tried to capitalize on a mother’s desire for healthy children. And they pushed back against the image of the tyrannical “King Coal” that had come about amid strikes by miners protesting dangerous, degraded working and living conditions as well as the rise of black lung disease.
In response, coal companies doubled down on the fantasy of “clean” coal.
An American Electric Power ad in The Wall Street Journal in 1976 talked about cleaning coal. Wall Street Journal archive
A 1979 advertisement for American Electric Power, for example, flew in the face of Clean Air Act mandates that coal corporations employ “scrubbing” technology to remove sulfur dioxide from smoke – the ad depicted someone cleaning coal by hand.
In addition to ordering some coal plants to continue operating, the Trump administration has pulled out old coal promotion tactics from the past, including repeatedly referring to coal as “clean and beautiful.” One image inserts Coalie next to a coal-mining family that otherwise looks like an ad that could have appeared a century ago.
A 2026 promotion for the Office of Surface Mining Reclamation and Enforcement includes a cartoon family with ‘Coalie’ added to the picture, looking like a child’s toy. OSMRE
The myth of coal as healthy and family friendly has been around for centuries – but coal has never been clean, or cute.
Annie Persons 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.
It’s tough to avoid the current hype about the health benefits of injecting peptides. Although these substances – essentially, synthetic bits of protein in solution – have long made the rounds in the fitness world, their popularity has exploded. Social media influencers, podcasters, wellness clinics and online sellers promote peptides as a quick and easy way to build muscle faster, heal injuries more quickly, reduce inflammation, lose fat, sleep better and more.
But do these products actually work, and can people who use them be sure they are safe?
Two of the most-hyped peptides widely promoted for injury recovery are BPC-157 and TB-500, sometimes marketed together under the comic book-sounding nickname the “Wolverine stack.”
That stack is part of a much larger longevity and fitness boom in which vendors sell or promote many different peptide products, often for uses that have not been studied rigorously in people. Online, people swap dosing protocols, compare “stacks” and describe these compounds as shortcuts for everything from tendon recovery to fat loss and muscle gain.
Some peptide drugs are important, legitimate medicines. Insulin is one example. GLP-1 drugs are another.
The issue is not whether something is a peptide but whether it has gone through the long process that makes medicines credible: reproducible manufacturing, careful dose testing, clinical trials for a specific condition and ongoing safety monitoring.
BPC-157, TB-500 and other internet-hyped peptides have not gone through that process. Such peptides are often sold online as supplements, or as research-grade products made for laboratory use but not FDA-approved as a treatment for people.
That distinction matters, because it means that producers might prepare such peptides at different concentrations, using different solvents, stabilizers and other ingredients. In other words, one vial of what’s supposedly the same substance would not necessarily be the same as the next, even if it were made by the same producer. And there’s no requirement that manufacturers ensure that products are free of contaminants.
Different vials could thus potentially behave differently in the body and may carry different risks, such as infection. That is a big problem if people are injecting something sold online as a shortcut to recovery.
The evidence for BPC-157
BPC-157 was discovered in the early 1990s as an isolated version of a peptide fragment linked to compounds found in stomach acid.
Early research focused on benefits for the gut, but because some animal studies suggested the compound could help promote blood vessel growth, calm inflammation and support tissue repair, researchers years later began testing it in cell and animal models of tendon, ligament, muscle, bone and cartilage injury.
Some hints from those studies are promising, which is why influencers and scientists got excited about BPC-157.
But in humans, the evidence is extremely thin. In fact, for common sports and orthopedic injuries, it’s close to nonexistent, as my colleagues and I found when we reviewed the published literature on BPC-157 for musculoskeletal healing in 2025.
The one published study we found in people included only 16 participants with knee pain. It relied on their self-assessment to gauge improvement and didn’t compare the group that received the peptide to one that did not. Those flaws made it impossible to tell whether the improvement was due to placebo effects, because many injuries get better over time anyway, or from the peptides.
Other reviews uncovered similar limitations: For musculoskeletal injuries, the studies in people are too sparse and low quality to pin down whether the peptide works or what risks it poses.
Basic, practical questions remain, too – such as what dose people should use, how long the compound lasts in different tissues and whether the product in a purchased vial actually matches its label.
TB-500 claims are even harder to evaluate
TB-500 has a slightly different story. It is usually marketed as a synthetic product related to a naturally occurring peptide called thymosin beta 4, which is found in many tissues.
Thymosin beta 4 has attracted scientific interest because it appears to be involved in processes relating to tissue repair, including cell movement, how new blood vessels form and how tissues respond to injury. Animal studies suggest it may support bone healing after fractures as well as muscle repair.
Here’s the issue, though: TB-500 is a smaller piece of thymosin beta 4. This means that research on thymosin beta 4 does not necessarily show that TB-500, the version most commonly sold online, helps a person recover faster from a tendon, muscle or joint injury.
Another complication is that the biological processes thymosin beta 4 seems to promote, such as new blood vessel growth and cell migration, don’t just occur in bone or muscle healing. They also play a role in other contexts, such as scarring, abnormal tissue growth and cancer biology.
This does not prove harm, but it does mean these are not simple, risk-free recovery supplements. Human studies don’t just have to show that thymosin beta 4, TB-500 or products sold under that name help people recover from common sports injuries, but also that these products are safe for long-term use.
So far, data on safety is scant. A recent analysis of more than 12,000 Reddit posts about using BPC-157 and other peptides after musculoskeletal injuries or surgery found that users frequently raised concerns about side effects, product purity and long-term safety. For example, some users reported injection-site reactions, diarrhea and emotional numbness. Studies like this one rest on low-quality, anecdotal evidence, but it’s the only evidence available for most of these peptides.
How to think about bold peptide claims
What makes the current peptide craze so confusing is that BPC-157 and TB-500 are not miracle cures, but they are not pure nonsense either. They sit in a more uncomfortable middle ground: interesting biology, intriguing findings in animal studies and, realistically, no convincing proof that they promote musculoskeletal healing in people.
In other words, peptides on the whole can be real medicines. But that does not mean the vial being marketed online is a safe, tested treatment for an injured shoulder, Achilles tendon or knee.
When you encounter wellness influencers or online sellers promising the glamour of faster healing, better recovery or a more aesthetic body, a few mundane questions can help cut through the marketing:
Has this exact product been tested in people with my injury?
Was it studied at the same dose and by the same route being marketed online?
Do I know exactly what is actually in the vial?
Is the promised benefit strong enough to justify the risk of using a product that has not cleared the usual standards for drug quality and evidence?
For now, none of those questions yield a clear, positive answer.
Flynn McGuire 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.
Source: The Conversation – (in Spanish) – By Josep M. Trigo Rodríguez, Investigador Principal del Grupo de Meteoritos, Cuerpos Menores y Ciencias Planetarias, Instituto de Ciencias del Espacio (ICE – CSIC)
Ilustración del cuerpo transneptuniano 2002 XV93 ocultando una estrella. / NAOJ / Ko Arimatsu, CC BY
Un pequeño objeto helado, situado más allá de Plutón y de la órbita del planeta Neptuno, ha sorprendido a los astrónomos al revelar, durante la ocultación de una estrella, que posee una tenue atmósfera. El hallazgo, logrado gracias a una campaña internacional liderada desde Japón y apoyada por astrónomos aficionados, desafía las teorías actuales sobre cómo los cuerpos pequeños del sistema solar, mucho más pequeños que Plutón, pueden mantener una envoltura gaseosa.
Cómo se ha encontrado
Profundizar en el conocimiento científico de objetos lejanos requiere estrategias muy originales y quizá inesperadas para el gran público.
Por ejemplo, a veces, los astrónomos observamos cómo una estrella o parte de ella “se oculta” brevemente cuando un planeta, un asteroide u otro objeto lejano del sistema solar pasa por delante de ella. Estos fenómenos reciben el nombre de “ocultaciones”, y los estudiamos mediante campañas internacionales de observación que nos permiten detectar detalles. Por ejemplo, si tienen anillos, satélites o incluso atmósferas, como acaba de ocurrir.
Utilizamos esta técnica desde hace unas décadas para aprender más sobre la forma, tamaño y propiedades de algunos de los cuerpos más alejados de nuestro sistema planetario: los objetos transneptunianos (TNO), aquellos que están más allá de la órbita de Neptuno.
Un nuevo Plutón
Hasta ahora, el único TNO con una atmósfera detectada era Plutón, con un tenue envoltorio cuya presión media se sitúa en torno a 10 microbares (μbar). Es decir, 100 000 veces menor que la de la Tierra. En las investigaciones de otros objetos situados más allá de Neptuno, con más de 500 km de diámetro, no se habían encontrado coberturas de gases, pero había podido calcularse un “límite máximo” para una posible atmósfera. Es decir: si existía, debía de ser extremadamente tenue, con presiones entre 1 y unos cientos de nanobares (nbar).
Se habían encontrado otros casos sin explicación. Por ejemplo, en Makemake, objeto transneptuniano catalogado como (136472). Con un diámetro de 1 430 km, es uno de los TNO de mayor tamaño y parece estar a día de hoy emitiendo metano, aunque el origen de ese envoltorio gaseoso de hidrocarburos sigue siendo incierto. ¿Quizás se debe al criovulcanismo? Sobre todo, brinda un buen ejemplo de los misterios que aún esconden cientos de cuerpos helados almacenados en la distante región transneptuniana, aunque no el último.
Un descubrimiento inesperado
En 2002 se descubrió un objeto transneptuniano con una órbita ligeramente excéntrica, que lo sitúa a distancias del Sol variables entre 34 y 44 unidades astronómicas; es decir, unas 40 veces más lejos del Sol que la Tierra, en promedio. Este lejano cuerpo helado, identificado provisionalmente como (612533) 2002 XV93, tiene un diámetro aproximado de 500 km.
La comunidad científica ha seguido a este objeto desde su descubrimiento, y nunca había revelado un comportamiento anómalo. Sin embargo, el 10 de enero de 2024 se realizó desde Japón una campaña para su seguimiento en un momento en el que se iba a producir una ocultación estelar, y los resultados no pudieron ser más sorprendentes: demostró que se encuentra envuelto en una atmósfera fina.
Es un hallazgo relevante porque demuestra que un TNO con un tamaño inferior al que se considera técnicamente un cuerpo planetario (en torno a 1 000 km) puede albergar, al menos de manera transitoria, una atmósfera.
El descubrimiento desafía los escenarios estándar de retención de gases volátiles y plantea muchas preguntas sobre la naturaleza de la atmósfera. ¿Cómo es posible que este pequeño objeto la tenga? Tal vez mantiene una actividad criovolcánica continua. O, quizá, podría ser consecuencia de un impacto reciente con otro objeto helado, similar a un cometa, que habría liberado una nube de material volátil que rodea al cuerpo de forma temporal. Sea cual sea el caso, el descubrimiento incrementa el interés en el estudio de esos objetos distantes.
Hilar fino
La técnica de las ocultaciones de estrellas por TNO no es trivial. Primero hay que predecir con gran precisión astrométrica cuando van a producirse las ocultaciones; después, comprobar si la sombra del objeto sobre la estrella puede observarse desde alguna región del globo terráqueo.
Los astrónomos recurrimos muy a menudo a la colaboración de aficionados, dado que para tener éxito en el seguimiento de estos fenómenos es necesario seguir cada ocultación desde un gran número de observatorios o lugares improvisados para la ocasión, distribuidos lo más homogéneamente posible sobre la superficie terrestre. La clave radica en que puedan trazarse muchas “cuerdas observacionales” que den cuenta si la distancia a ese pequeño astro en concreto enmascara una atmósfera, anillos o, incluso, algún satélite.
Otro aspecto interesante de este descubrimiento es que se ha realizado gracias a una colaboración profesional-amateur. Con excepción de un telescopio profesional, el resto de las observaciones se han obtenido con telescopios portátiles del tamaño más común entre los aficionados, obviamente dotados con cámaras digitales adecuadas para el seguimiento de estos fenómenos súbitos que requieren una gran precisión temporal.
A pesar de que la ocultación estelar fue positiva sólo desde tres lugares diferentes, ejemplifica el papel fundamental que pueden tener los astrónomos aficionados, particularmente en el campo del estudio de los cuerpos menores del sistema solar.
Josep M. Trigo Rodríguez recibe fondos del proyecto del Plan Nacional de Astronomía y Astrofísica PID2021-128062NB-I00 financiado por el MICINN y la Agencia Estatal de Investigación.
Au fond de la lagune de Thau, en Occitanie, la source de la Vise est régulièrement sujette à un phénomène dit d’inversac, où la source d’eau douce se met soudainement à absorber l’eau saumâtre. Ce mécanisme, jusque-là peu connu, expose les ressources en eau douce des côtes à un risque de salinisation. Grâce à un dispositif expérimental unique, des chercheurs français ont pu l’observer en direct. De quoi expliquer au passage pourquoi certaines villes des alentours souffrent, lors de ces épisodes, d’inondations en l’absence de pluies.
Un phénomène exceptionnel, appelé « inversac », menace les ressources d’eau souterraine autour de l’étang de Thau (une vaste lagune d’eau saumâtre) en Occitanie. En fonction des conditions météorologiques, la source sous-marine de la Vise (surnommée localement « le Volcan » ou « le Gouffre ») peut s’interrompre – et cesse alors momentanément d’apporter de l’eau douce dans la lagune.
Elle devient dès lors un point d’infiltration majeur d’eau salée de la lagune vers l’aquifère, provoquant une salinisation chronique des eaux souterraines si précieuses, et des épisodes d’inondation sans pluie dans la station thermale de Balaruc.
Avec des collègues, nous avons pu suivre le phénomène en direct grâce à des instruments spécifiques, une première mondiale, qui a notamment fait l’objet d’une publication scientifique en 2025. De quoi mieux comprendre les causes de ce phénomène jusque-là mystérieux, qui peut durer des mois : six mois pour les épisodes survenus en 2010 et en 2014, et même dix-huit mois pour celui survenu entre 2020 et 2022.
En zone côtière, les exutoires des eaux souterraines peuvent être sous-marins
Les eaux de pluie qui s’infiltrent à la surface de la terre rejoignent les nappes aquifères. Elles circulent ensuite dans le sous-sol jusqu’à des exutoires en surface : sources, zones humides et lits des rivières constituent autant de points bas du paysage vers lesquels convergent les eaux souterraines.
Dans la calanque de Port-Miou, seul un léger courant à peine visible en observant l’écume formée par les vagues contre les rochers indique la présence d’un débit de plusieurs mètres cubes par seconde, quelques mètres sous la surface de la mer. L’eau presque douce (plus légère que l’eau très salée de la Méditerranée) forme une nappe froide sur la mer, plus chaude en été. Xerti, CC BY-SA
En zone côtière, les exutoires des eaux souterraines peuvent être sous-marins, situés dans la mer ou dans des lagunes côtières. Jouant un rôle important pour les écosystèmes marins côtiers, ils sont diffus ou ponctuels selon le type d’aquifère. Dans ce dernier cas, le plus souvent en contexte karstique, il s’agit de sources sous-marines. Elles sont particulièrement nombreuses en Méditerranée grâce à la forte présence de roches calcaires propices aux phénomènes karstiques.
Plus à l’Ouest, dans l’Hérault, il existe plusieurs autres sources sous-marines qui émergent dans la lagune de Thau. Parmi elles, la source sous-marine de la Vise, située au large de Balaruc, draine un aquifère côtier primordial pour les habitants de cette région au climat chaud et sec de type méditerranéen.
Géographie de la source sous-marine de la Vise. En (a), la localisation de la source dans la lagune de Thau, en (b) une vue en plan du cône (anomalie bathymétrique liée au débit d’eau de la source) autour de la source au large de Balaruc et enfin en (c) vue en coupe du cône et du point d’émergence (griffon) de la source. Fourni par l’auteur
En effet, les eaux souterraines y sont prélevées pour l’alimentation en eau potable des villages voisins, pour l’irrigation aussi, mais surtout elles alimentent les thermes de Balaruc-les-Bains, première station thermale de France en nombre de curistes. Malheureusement, cette ressource d’eau douce précieuse est menacée par un phénomène exceptionnel : l’inversac.
L’inversac, ou quand les flux d’eau s’inversent et une source absorbe l’eau saumâtre
Bien connue des pêcheurs et des ostréiculteurs, la source de la Vise est située dans la lagune de Thau, à une profondeur de 30 mètres au large de Balaruc. Cette profondeur est exceptionnelle pour l’étang de Thau, dont la profondeur moyenne excède rarement 4 m à 5 m : les flux d’eau souterraine ont creusé et érodé la roche pour créer un grand cône sous-marin situé autour de l’émergence. Cette profondeur attire les amateurs de plongée sous-marine qui peuvent ainsi pratiquer leur sport au cœur d’un site remarquable.
La source est localisée au sommet d’un conduit karstique subvertical qui relie la lagune de Thau à une nappe aquifère captive (c’est-à-dire sous pression) située en profondeur dans les calcaires du Jurassique. Le débit de la source est généralement de l’ordre de 100-150 litres par seconde (l/s), et augmente avec le niveau d’eau dans la nappe après des pluies intenses. C’est une eau douce et chaude (20 °C), car réchauffée par les flux d’eau d’origine profonde qui alimentent également la station thermale de Balaruc.
Or, depuis la fin des années 1950, on observe des épisodes temporaires d’inversion des flux d’eau au niveau de la source. Le résultat ? Une interruption brutale de l’arrivée d’eau douce d’origine souterraine, suivie d’une absorption des eaux de la lagune par la source. En hydrologie karstique, ce phénomène est connu sous le nom d’inversac, nom qui désigne une cavité karstique alternativement absorbante ou émissive, selon les conditions hydrologiques.
Depuis la fin des années 1950, la source de la Vise a commencé, à plusieurs reprises, à absorber l’eau saumâtre de la lagune.
La plupart du temps, les inversacs sont des pertes-émergences situées le long d’une rivière : selon les niveaux d’eau, la rivière s’infiltre dans la cavité karstique (fonctionnement en perte) ou alors cette dernière déverse de l’eau dans la rivière (fonctionnement en émergence).
Dans le cas de la Vise, l’inversac se produit en lien avec l’étang de Thau. Selon les conditions hydroclimatiques, la source va tantôt déverser l’eau douce, tantôt absorber l’eau salée de l’étang.
Explication du mécanisme d’inversac (a) en régime normal, la pression au sein de l’aquifère captif est supérieure à la pression exercée par le niveau d’eau dans la lagune, les flux d’eau sont ascendants au sein du conduit karstique (b) lorsque la pression au sein de l’aquifère devient inférieure à la pression de l’étang, les flux deviennent descendants et la source absorbe l’eau de l’étang (régime d’inversac). Fourni par l’auteur
Un dispositif de mesure unique au monde
Pour mieux comprendre ce phénomène, les hydrogéologues du BRGM, en collaboration avec la société ANTEA, ont conçu un dispositif inédit spécialement consacré à la mesure des débits de la source sous-marine. Il s’agit d’un tube d’une longueur d’environ cinq mètres et d’un diamètre d’un mètre, posé sur l’émergence, composé de trois compartiments.
(a) Position du dispositif sur le griffon de la source sous-marine de la Vise, (b) vue descriptive du dispositif. Fourni par l’auteur
Le tube inférieur récolte l’eau douce sortant des principaux griffons (points d’émergence) présents au fond de la lagune. Au-dessus, un débitmètre électromagnétique permet de mesurer le débit vertical au sein du tube intermédiaire. Il est surmonté d’un tube de tranquillisation destiné à réguler les flux d’eau et à réduire les turbulences pour assurer une bonne qualité de la mesure du débit. Des capteurs de température, de salinité et de pression sont installés dans le dispositif pour compléter les mesures.
Un inversac observé en direct en novembre 2020
Installé en juin 2019 par des scaphandriers professionnels, il a permis d’observer en direct un inversac qui s’est produit le matin du 27 novembre 2020. En effet, à 9 h 40 exactement, le débit de la source s’est brutalement inversé : d’un débit ascendant d’environ 120 l/s, il est passé à un débit descendant de 350 l/s.
Simultanément, les capteurs ont mis en évidence la présence d’une eau complètement différente : une eau salée et froide (comme la lagune) s’est substituée, au sein du tube de mesures, à l’eau douce et chaude qui provenait précédemment de la nappe aquifère. À cet instant, la source a commencé à absorber l’eau de la lagune, qui a envahi progressivement la nappe aquifère.
Cet inversac a duré seize mois, durant lesquels environ 7 millions de mètres cubes d’eau salée se sont infiltrés, provoquant l’intrusion de 200 000 tonnes de sel dans l’aquifère. En 2014, la salinisation progressive de la nappe provoquée par la succession des inversacs a nécessité la fermeture du captage d’eau souterraine de Cauvy, qui alimentait en eau potable Balaruc-les-Bains.
La répétition successive des inversacs menace également la ressource en eau thermale, dont l’usage est important pour l’activité économique du secteur. Plusieurs maraîchers exploitants ont également arrêté leur activité à cause de la salinisation de leur puits, tandis que de nombreux forages domestiques ont été touchés. Le sel est aussi remonté dans les sols, menaçant les espaces verts en affaiblissant un grand nombre d’arbres de la commune.
En complément des mesures à la source de la Vise, un réseau d’observation a été installé pour surveiller les niveaux d’eau de la lagune et de la nappe aquifère.
L’analyse détaillée de toutes ces données a permis de montrer que l’inversac s’est enclenché à un moment bien particulier, où une tempête marine accompagnée d’un coup de vent marin avait induit une hausse du niveau de l’étang. Et cela, au moment même où, au contraire, le niveau de la nappe aquifère était au plus bas, par manque de précipitation et de recharge. Résultat : la pression exercée par la masse d’eau salée de l’étang est devenue plus élevée que la pression de la nappe : les écoulements d’eau se sont alors brusquement inversés. C’est ce mécanisme que nous avons décrit dans notre article publié dans la revue Nature Communications Earth and Environment.
« Bouchon de sel » et inondations sans pluie
Restait à expliquer une bizarrerie locale : alors que les inversacs se déroulent en période de sécheresse, lorsque le niveau de la nappe aquifère est au plus bas, ils sont systématiquement accompagnés d’inondations dans la ville de Balaruc-les-Bains. Ceci est d’autant plus étonnant qu’aucun épisode de pluie ne précède ces inondations qui frappent les sous-sols, les caves et les parkings souterrains de la commune, causant de nombreux dégâts.
Cette curiosité hydrologique est à rapprocher des mesures observées dans les piézomètres des environs : chaque inversac est suivi d’une augmentation rapide des niveaux d’eau de la nappe d’environ 2,3 m. Cette hausse est expliquée par le contraste de densité entre les eaux : l’eau salée de la lagune est environ 3 % plus lourde que l’eau douce.
Ainsi, au moment de l’inversac, le conduit karstique vertical se remplit en quelques minutes d’eau salée sur sa hauteur totale, estimée à environ 70 m. Il en résulte une augmentation brutale de 2,3 m de la pression exercée par la lagune sur la nappe aquifère. Cette onde de pression se propage ensuite rapidement dans la nappe aquifère captive jusqu’à plusieurs kilomètres en quelques heures, provoquant une hausse des niveaux d’eau, et donc des inondations, même en l’absence de pluie.
Cette hausse inattendue des niveaux d’eau explique l’apparente contradiction entre la soudaineté du déclenchement d’un inversac et sa très longue durée. Si un coup de vent sur l’étang provoquant une hausse de son niveau de quelques centimètres peut déclencher un inversac, il ne suffit pas d’une accalmie météorologique pour que le système revienne à son état normal initial. Pour retrouver des flux ascendants dans le conduit karstique, la pression de la nappe aquifère doit vaincre cette surpression de 2,3 m provoquée par l’intrusion de sel, qui agit alors comme une sorte de « bouchon » sur la source sous-marine.
De ce fait, seule une très forte pluie sur le causse d’Aumelas, sur les hauteurs du bassin de Thau, peut recharger suffisamment la nappe aquifère pour provoquer une augmentation de niveau supérieure à 2,3 m, capable de vaincre le bouchon de sel. C’est ce qui s’est déroulé le 14 mars 2022 lorsqu’un épisode pluvieux de plusieurs jours, supérieur à 100 millimètres, a mis fin à cet inversac.
Depuis les années 1950, les inversacs se répètent et s’accélèrent. En cause, les pompages d’eau souterraine, mais surtout la succession des sécheresses, qui provoquent une baisse du niveau de la nappe. Jusqu’à présent, le système revient toujours à son état normal après quelques mois, mais qu’en sera-t-il dans le futur lorsque la recharge naturelle déclinera et que le niveau de la mer montera ?
Il n’est pas exclu que le système bascule définitivement en inversac, provoquant ainsi une salinisation complète et définitive de l’aquifère du Jurassique. C’est pour cette raison qu’un projet d’expérimentation est en cours avec le Syndicat mixte du bassin de Thau pour explorer les moyens possibles de réduire les effets d’un inversac et de préserver la nappe aquifère.
Cette étude a pu être menée dans le cadre du projet de recherche DEM’Eaux Thau (2017-2022).
D’un montant de 5,3 millions d’euros, le financement du projet DEM’Eaux Thau a été assuré à 42% par le ministère de l’Enseignement supérieur et de la Recherche et la Région Occitanie (dans le cadre du Contrat de Plan Etat-Région 2015-2020), à 11% par le fonds européen FEDER, à 17% par l’Agence de l’eau Rhône-Méditerranée-Corse, à 4% par Montpellier Méditerranée Métropole, à 2% par Balaruc-les-Bains et à 1% par le Syndicat Mixte du Bassin de Thau. Le reste du financement du projet (23%) a été apporté grâce à la participation financière de la plupart des partenaires
Bernard Ladouche et Claudine Lamotte ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’ont déclaré aucune autre affiliation que leur poste universitaire.
La photosynthèse fixe le carbone atmosphérique sous forme de molécules organiques essentielles à la vie et produit l’oxygène présent dans l’atmosphère et dans les mers. Elle a été acquise par le monde vivant grâce à des intégrations cellulaires successives en « poupées russes », les photosymbioses. En mimant les étapes précoces des photosymbioses, nous suggérons, dans notre article publié dans Current Biology, que l’oxygène serait un facteur déterminant pour les amorcer en milieu hypoxique (c’est-à-dire à faible teneur en oxygène) – la fourniture de carbone pouvant être un évènement secondaire.
En convertissant le rayonnement solaire en énergie utilisable par le monde vivant, la réaction de photosynthèse a profondément modifié l’ensemble de la planète Terre. La photosynthèse permet la conversion du carbone provenant du dioxyde de carbone (CO₂) atmosphérique en matière organique complexe, principalement sous forme de sucres qui alimentent une grande partie des formes de vie, dont les sociétés humaines. Une autre conséquence de la photosynthèse, qui a eu des conséquences majeures à l’échelle planétaire, est la production d’oxygène. Celle-ci est causée par la cassure de molécules d’eau qui initie le flux énergétique d’électrons qui permet la fixation du carbone en sucres.
La photosynthèse oxygénique est apparue chez un groupe particulier de bactéries, les cyanobactéries, dont des traces fossiles remontent à 3,8 milliards d’années et dont des descendants existent encore aujourd’hui. L’oxygène produit a permis le métabolisme aérobie, plus énergétique, qui a conduit à l’émergence d’organismes unicellulaires prédateurs. Certains ont intégré des cyanobactéries, bénéficiant à leur tour de la photosynthèse, c’est ce que l’on appelle la photosymbiose. Les lointains descendants de ces organismes sont devenus les algues et les plantes actuelles.
Des emboîtements en « poupées russes » secondaires et tertiaires
L’histoire ne s’arrête pas là puisque, à plusieurs reprises, d’autres organismes prédateurs ont intégré ceux déjà issus de la première photosymbiose, créant des emboîtements en « poupées russes » secondaires et tertiaires. Par exemple, les coraux, apparus il y a environ 500 millions d’années, sont des animaux hébergeant des organismes photosynthétiques unicellulaires issus d’une photosymbiose secondaire, les dinoflagellés.
Nous avons développé un système expérimental permettant l’évolution en laboratoire d’étapes précoces de la transition entre une relation prédateur-proies vers une relation hôte-photosymbionte. Il comprend un organisme unicellulaire prédateur du groupe des ciliés, Tetrahymena thermophila et des proies photosynthétiques. Les ciliés sont des unicellulaires, très abondants dans les écosystèmes aquatiques, dont font partie les paramécies. la cyanobactérie Synechoccoccus elongatus permet de mimer les événements de photosymbiose primaire et la microalgue verte eucaryote Chlorella variabilis permet de mimer les événements de photosymbiose secondaire.
Des cellules de Tetrahymena thermophila ont phagocyté des algues unicellulaires (Chlorella variabilis), celles-ci ne sont pas digérées et peuvent fournir de l’oxygène issu de la photosynthèse. Fourni par l’auteur
Grâce à la fluorescence naturelle des organismes photosynthétiques, nous avons combiné la microscopie et la cytométrie de flux, qui permet de quantifier et de trier des cellules suivant leur taille ou leur fluorescence pour observer le trajet des proies à l’intérieur des cellules prédatrices.
Une gloutonnerie extraordinaire
Nous avons ainsi caractérisé cette dynamique de la phagocytose jusqu’à l’élimination sous forme de boulettes fécales. Ceci a montré la gloutonnerie du prédateur unicellulaire qui peut ingérer jusqu’à 160 cyanobactéries ou 40 microalgues en moins d’une heure et les éliminer progressivement pendant plusieurs heures. Curieusement, de nombreuses proies sont rejetées sans être digérées totalement, voire pas du tout, suggérant qu’une transition simple entre l’état de proie et celui de symbionte intracellulaire ne nécessiterait que l’interruption de la rejection.
Afin d’évaluer les conditions environnementales permettant l’initiation d’une symbiose, nous avons placé le prédateur et ses proies dans des milieux pauvres en carbone assimilable ou en absence oxygène, et mesuré la survie du prédateur. Nous avons ainsi montré que les proies photosynthétiques favorisent considérablement la survie en milieu hypoxique alors qu’elles procurent un avantage faible, voire inexistant, dans un milieu pauvre en carbone. L’hypoxie induit aussi une condition physiologique atténuant sa propre cause, puisque le transit intracellulaire des proies est considérablement ralenti, favorisant ainsi l’utilisation de l’oxygène produit par la photosynthèse des proies.
Ce résultat n’était pas vraiment attendu, car il est généralement admis que le moteur principal des photosymbioses est la fourniture de carbone sous forme de sucres. Nous montrons donc que la production d’oxygène en conditions hypoxiques peut être une cause primaire de l’amorce d’une symbiose photosynthétique.
Les milieux hypoxiques ont été prépondérants pendant une grande partie de l’histoire de notre planète et sont toujours fréquents, en particulier dans les environnements aquatiques et marins. Leur incidence augmente même sous l’influence de perturbations anthropiques et de l’augmentation des températures. L’exploration de ces milieux pourrait donc révéler de nouvelles associations photosymbiotiques. Nous anticipons maintenant que le système expérimental que nous avons développé nous permettra d’étudier les mécanismes moléculaires et cellulaires stabilisant une proie en symbionte, qui restent largement inconnus. Au-delà de la compréhension d’un mécanisme fondamental d’association entre organismes ces travaux pourraient avoir des applications de biologie synthétique, pour construire, par exemple, de nouvelles associations productrices de biocarburants.
Christophe Robaglia a reçu des financements de l’ANR, Projet-ANR-21-CE20-0035 PHOCEE
Gaël Brasseur et Loïc Quevarec ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’ont déclaré aucune autre affiliation que leur poste universitaire.
The cruise ship cluster of hantavirus cases continues to grow. The World Health Organization reports that as of May 6 there were eight cases, three of whom are confirmed by laboratory testing as hantavirus. In recent days, we heard three passengers had died.
Now some passengers are being medically evacuated from the cruise ship MV Hondius. Other passengers have disembarked and are returning home. Swiss authorities have confirmed a passenger on the ship is now a confirmed case and is receiving care in a Zurich hospital.
I’m a public health physician with a special interest in respiratory diseases. I’ve also investigated a hantavirus outbreak.
Here’s what investigators want to know about the current cluster of cases. This includes gathering evidence to see if the virus is transmitting from person to person.
Back in 1993, there was an unknown pathogen
In 1993, I was a young epidemic intelligence service officer working at the United States Centers for Disease Control. I was deployed to the deserts of the south-western US to help investigate a frightening outbreak, mainly among Navajo people.
Adults in their 20s and 30s were becoming suddenly unwell. They would develop a fever and cough, then rapidly progress to severe respiratory failure as fluid leaked into their lungs. Some appeared well enough to be dancing in the evening and were dead within hours.
The investigation team was nervous. We did not yet know the pathogen, how it was spreading, or whether we were at risk.
One of the first recognised cases was a well-known runner, so we initially wondered whether infection might be linked to inhaling something stirred up in desert dust. A leak from a remote military biowarfare laboratory was also considered, as was plague that was endemic to the area.
After laboratory testing, the cause was identified as a new hantavirus, later known as Sin Nombre virus. The virus attacked the small blood vessels of the lungs and was linked to exposure to the urine, faeces and saliva of infected deer mice. Mice numbers had increased dramatically and were entering homes and workplaces across affected communities.
A crucial finding was that, like most hantaviruses, Sin Nombre virus did not appear to spread from person to person. Family clusters were explained by shared exposure to rodents or rodent-contaminated environments, especially during cleaning or other close contact with contaminated objects or dust.
That is why many of us were surprised years later when Andes virus, a South American hantavirus, was shown to spread occasionally from person to person.
This remains uncommon, but it has been documented, including in outbreaks in Argentina – the country from which the MV Hondius departed before the current suspected outbreak.
What would a disease detective do now?
The first step in any outbreak investigation is to confirm the diagnosis. At this stage, the difference between a “suspected” and “confirmed” case still matters.
Investigators need to know whether all severe respiratory illnesses in the cluster are due to hantavirus, or whether confirmed cases are occurring against a background of another infection, such as influenza or COVID.
The next step is to build a timeline. The timing of when symptoms started is often the first clue to where and how people were exposed.
According to WHO, the ship departed Ushuaia, Argentina, on April 1 2026. The first known case developed symptoms on April 6. Other cases developed symptoms later in April.
Hantavirus pulmonary syndrome describes the respiratory symptoms that follow after the type of hantavirus infection that mainly attacks the lungs. These typically develop two to four weeks after exposure. However, illness can appear as early as one week and as late as eight weeks after infection.
That makes the first case difficult to explain as an exposure acquired on the ship after departure. Symptoms started on April 6, only five days after leaving Argentina. That’s shorter than the usual incubation period (the period from infection to showing symptoms) and even shorter than the lower end commonly cited.
So for that case, it’s more plausible for that person to have been exposed in Argentina before boarding. There are emerging reports of a bird-watching activity that might have led to rodent exposure.
The later cases are more ambiguous. They could have been exposed before departure, or during shore activities in Argentina, or elsewhere. But their timing also raises another possibility: transmission from the first case to close contacts on board.
This is where the epidemiology becomes interesting.
Did the virus spread from person to person?
The second case was a close contact of the first. This creates two plausible explanations. They may have both been exposed to the same infected rodent (or its urine or droppings, for example). Alternatively, it’s very likely the second case contracted the infection from the first case.
The third case was not part of that same close family unit. If investigators find this person shared the same excursions in Argentina as the first two, the outbreak may still be explained by a common source. But if there was no shared rodent exposure, suspicion of person-to-person transmission increases.
This does not mean person-to-person transmission is proven. It means it becomes one of the leading hypotheses to test.
If human-to-human transmission is not the explanation, investigators would need to consider a less tidy chain of events.
The first case would have had a pre-boarding exposure with a short incubation period. The second case would need either the same exposure with a longer incubation period, or infection from the first case.
The third case would need either an independent exposure to infected rodents before boarding, or another exposure during the voyage. None of these is impossible. But as more cases appear, and if they cluster in time around contact with earlier cases, the human-to-human hypothesis becomes harder to dismiss.
The approximate gap between the first case’s illness and the later cases is also important. If person-to-person transmission is occurring, severe hantavirus illness is likely to coincide with a higher risk of being infectious and infecting others. So we would expect symptoms that start two to three weeks after close contact with an earlier severe case, and this is what we’re seeing from the cruise ship.
What are the public health implications?
The practical public health response must therefore cover both possibilities: a common environmental source and limited person-to-person spread.
That means detailed interviews about pre-boarding travel, shore excursions, wildlife exposure, rodent sightings, cabin locations, cleaning activities, shared dining, shared transport, and close contact with ill passengers.
It also means laboratory confirmation in multiple cases, sequencing of viral samples where possible, and careful reconstruction of who had contact with whom, and when.
Genetic fingerprinting can explore if the virus has the same historical mutation that allowed human-to-human transmission to emerge in previous outbreaks (which were easily controlled with basic isolation and infection control). If a new mutation was found, this would raise concerns of greater transmission risks.
For the public and health authorities considering receiving the passengers from the quarantined ship, the key message is not to panic.
Most hantaviruses are not spread between people. Even with Andes virus, person-to-person transmission is uncommon and usually requires close or prolonged contact. WHO currently assesses the risk to the global population as low. This virus does not spread like influenza or COVID.
But for outbreak investigators, this is exactly the sort of cluster that demands disciplined shoe-leather epidemiology: confirm the diagnosis, build the timeline, test the competing hypotheses, and let the pattern of exposure, illness and laboratory evidence tell the story.
Craig Dalton receives funding from the Commonwealth Department of Health, Disability and Ageing.
La primavera y el verano es época de avispas, eso seguro. Molestas, irritantes, muchas veces construyen sus nidos en zonas urbanas, bajo tejados, en jardines y en diversas estructuras. Una situación que genera mucha interacción con los humanos, con riesgo de picaduras y problemas derivados si no tenemos cuidado.
Existen poco más de un centenar de especies de véspidos en toda España. La mayoría son especies solitarias, como las avispas alfareras, que a menudo pasan desapercibidas. Más conocidas son, sin embargo, las avispas sociales, como las papeleras, con sus nidos de celdas hexagonales, que construyen con material vegetal y agua.
A menudo no las aceptamos, pero hay que decir que desempeñan un papel importante en muchas interacciones de la naturaleza, ya sea como depredadoras o como polinizadoras; unos roles estratégicos para la estructura y el equilibrio de las redes de interacción en la naturaleza.
La avispa asiática sale de su refugio en primavera
La mayoría de estas avispas son autóctonas, pero en los últimos años se han añadido especies exóticas que llegan por acción voluntaria o involuntaria de los humanos, como es el caso de la avispa asiática (Vespa velutina).
No ha sido una aparición natural, sino provocada por el movimiento de mercancías desde China, con la primera detección en Francia en 2004. Desde entonces se ha extendido rápidamente por toda Europa, a una media de 50–60 km anuales. Se considera una especie invasora, especialmente por sus impactos demostrados sobre el sector primario de la apicultura.
Las claves de su éxito son que tienen pocos competidores, depredadores y parásitos, y que encuentran los recursos necesarios para aumentar su abundancia y ampliar su distribución.
La avispa asiática presenta un ciclo de vida de un año. Las reinas fecundadas del año anterior, que salen de sus refugios invernales hacia febrero-marzo, construyen por sí solas los nidos embrionarios en lugares protegidos, a poca altura.
¿Cuáles son sus escondites?
En ellos ponen los primeros huevos fecundados, de los que nacen las avispas obreras. A partir de ese momento, la reina ya no sale del nido. Serán las obreras quienes trabajarán e iniciarán la búsqueda de los recursos necesarios (azúcares, proteína, celulosa y agua) para hacer crecer el nido hacia un nido primario.
Más adelante, generalmente construirán un segundo nido más grande, llamado secundario. Lo harán en una zona más elevada, como copas de árboles, cornisas de edificios, salientes de paredes o cuevas en acantilados. Es aquí, ya hacia el otoño, cuando aparecen los machos (de huevos no fecundados) y las reinas vírgenes. Los machos fecundarán a estas reinas, que se prepararán para pasar el invierno en algún lugar resguardado y protegido. El resto de la colonia va muriendo (reina vieja, obreras y machos) al entrar el invierno. Y así se inicia un nuevo ciclo.
Además del efecto social, con casos graves sobre la salud de las personas, el principal impacto demostrado de esta especie es sobre el sector de la apicultura, especialmente cuando los nidos son medianos o grandes en verano y otoño.
Las avispas visitan las granjas de colmenas para encontrar el “bufé libre” de proteína (la abeja de la miel,Apis mellifera) que necesitan para alimentar a sus larvas. Los visitan de forma periódica y recurrente.
La gran capacidad de dispersión de las nuevas reinas, que pueden volar varios kilómetros en un solo día, contribuye a la rápida expansión y a la presión constante sobre las granjas de colmenas.
Por todos estos motivos que se hace imposible su erradicación en las zonas donde ya ha llegado. Todo juega a su favor.
Mejores opciones para combatirlas
No hay estudios que demuestren que determinadas acciones sean efectivas para minimizar su impacto, como por ejemplo trampear reinas en primavera.
Ahora bien, sí se puede mejorar el manejo y la gestión de las granjas de colmenas in situ desde el sector de la apicultura, en función de la presencia de esta especie.
Los apicultores realizan trashumancia para evitar su presencia y ajustan temporalmente el movimiento de las colonias, o utilizan distintas herramientas para proteger las colmenas de la abeja de la miel, aunque presentan limitaciones, especialmente en periodos de alta presión.
Esta trampa está diseñada para capturar obreras y reinas de manera selectiva delante de las colmenas sin afectar a las abejas, permitiendo un control más sostenible y aplicable en granjas de distintos tamaños.
Toda la información científica disponible y la que se pueda generar en el futuro sobre la gestión de la avispa asiática es clave como estrategia para establecer protocolos que permitan su control, ya sea para reducir los riesgos para las personas, para otros polinizadores o para la protección de las colonias de abejas de la miel. En este último caso, no se compromete la producción de miel y otros productos apícolas, y se establece un control selectivo y sostenible.
La avispa asiática ha llegado para quedarse.
Josep Maria Bas Lay no recibe salario, ni ejerce labores de consultoría, ni posee acciones, ni recibe financiación de ninguna compañía u organización que pueda obtener beneficio de este artículo, y ha declarado carecer de vínculos relevantes más allá del cargo académico citado.
