On April 1, 2026, the cruise ship MV Hondius departed Ushuaia, Argentina. By May 7, there were seven cases on board of severe respiratory illness, including two lab-confirmed hantavirus cases, five suspected cases, and three deaths. One of the people who later died was also on a flight. From that same flight, a flight attendant was later hospitalized with hantavirus symptoms.
As of the writing of this article, to the best of my knowledge, all of the known infected passengers have been medically evacuated to various countries. Some exposed people left the ship before the outbreak was identified. And many people, both exposed and unexposed (though, at this point, maybe I should consider them all exposed) are continuing their journey on the ship to the Canary Islands.
So, what is Hantavirus?
Hantaviruses are a family of viruses carried primarily by rodents, especially mice and rats. Humans usually become infected by inhaling tiny particles contaminated with rodent urine, droppings, or saliva, often in enclosed spaces like cabins, sheds, barns, or poorly ventilated buildings. Imagine someone sweeping up a floor in a place where hantavirus is common and inhaling the bits of feces-contaminated dust that are raised by the broom. That’s not an unusual route of infection.
Different hantaviruses circulate in different parts of the world. In Asia and Europe, they more commonly cause a condition called hemorrhagic fever with renal syndrome (HFRS), which affects the kidneys and blood vessels. In the Americas, hantaviruses are better known for causing hantavirus pulmonary syndrome (HPS), a rare but potentially deadly illness that attacks the lungs and can rapidly lead to severe breathing failure.
Most hantaviruses do not spread easily between people. The major exception is the Andes virus strain found in parts of South America, which has shown limited human-to-human transmission in situations involving very close contact, such as among family members or caregivers. And I mean very close contact, like sleeping in the same bed, coughing in each other’s faces, or sharing bodily fluids.
Early symptoms of hantavirus infection resemble many common viral illnesses and include fever, fatigue, muscle aches, headache, nausea, and vomiting. In severe cases, patients can suddenly develop coughing and shortness of breath as fluid accumulates in the lungs. There is no widely available cure, so treatment focuses on supportive hospital care, especially oxygen and intensive respiratory support. Because the disease is uncommon but highly serious, outbreaks often attract intense scientific and media attention. Ahem.
Where Is It Most Common?
Hantavirus is found worldwide, but it is most common in parts of Asia and Europe, where thousands of cases occur every year. China alone accounts for more than 90% of HFRS cases. Europe reports roughly 1,500–5,000 cases annually, especially in countries like Finland, Germany, Sweden, and parts of Eastern Europe.
The Americas see far fewer total cases, but the cases are more serious. North and South America together usually report only a few hundred cases per year. Argentina and Chile are especially important because they harbor the Andes strain, the only hantavirus clearly shown to spread between humans. The United States has recorded about 1000 cases since national surveillance began in 1993.
According to the WHO:
- China: >90% of global reported HFRS cases
- Rest of Asia & Europe: most of the remaining global burden
- North & South America : probably <1% of global cases, mostly HPS types
- Worldwide estimates: roughly 10,000–200,000 infections annually, depending on surveillance methods and definitions used
How About Locally?
I’m in Canada, so when I mean “local”, I mean in Canada. And yes, there have been domestic cases here historically, almost always in Western Canada. Between 1989 and 2015, there have been 109 confirmed cases here. (Roughly a third of them died.) Cases here tend to happen during cleaning of sheds, barns, garages, cabins, or grain-storage areas. People in rural areas can inhale aerosolized mouse droppings or urine. And yes, there have been a handful of imported cases. But the majority are home-grown.
Importantly, Canada has never seen a case of the Andres strain, the one that can transmit human-to-human.
The USA, as noted, has seen about 1000 cases since surveillance began in 1993. (About 40% of those died.) Cases were mostly west of the Mississippi river (New Mexico, Colorado, Arizona, California, Washington, Montana). Just like in Canada, people got it from contact with rodent droppings. And yes, the Andes variety has appeared in the USA before, but to my knowledge only as imported cases, not domestic.
How Fatal Is it?
Ah yes, the question most people care about. And they should care about it. Hantavirus can be scary. The Asian/European variety (HFRS) has a case fatality ratio of 1–15%, depending on severity strain. While the American variety (HPS) is scarier at 30–40%, though some outbreaks have seen a 50% death rate. So, yeah, it’s scary if you get it.
Is There a Vaccine?
Why, yes, there is! I bet you’re surprised. China has several vaccines they have deployed to combat HFRS, and it’s thought that that is a main reason that their disease burden has come down in recent years. South Korea more famously developed Hantavax, made primarily for its military. If multiple doses are given, Hantavax seems to confer an efficacy of 25–75%.
But but but… and this is important… There is no vaccine for the HPS version of hantavirus. This is the version that currently is driving the cruise ship outbreak. Could we use Hantavax to prevent the HPS strain? There’s probably some cross-immunity, but the viruses are so different that most experts think the protection would be very limited.
So Why Is Everybody Freaking Out?
People are freaking out because it’s been confirmed that the cruise ship patients are indeed infected with the Andes strain. This means that not only is there no cure, no vaccine, and a fatality risk that is essentially a coin flip, but that there’s now the possibility of person-to-person transmission, a risk that does not present itself with the other hantavirus types.
So, for a public still recovering from the trauma of the global COVID-19 pandemic, this might seem like a burgeoning nightmare scenario. But this is not COVID or the Measles or the Flu. It’s actually comparatively quite difficult to contract hantavirus from another person. You need intimate contact. It’s not like you’ll get it from an infected person on the bus.
Having said that, I am aware of this 2018 super spreader event. So, as with all things, the science is evolving.
Well, the Flight Attendant Got it Somehow!
Did she, though? There are a lot of unknowns (as of the writing of this article) with respect to that case. Right now, we don’t know for sure that she even has hantavirus. She only has symptoms of something resembling hantavirus. We also don’t know the extent of her contact with the infected person on the plane. Did the passenger cough productively directly into her face? Did the flight attendant handle any of her vomit or saliva in the course of her work? We just don’t know yet.
What’s the Nightmare Scenario
That would be if the Andes strain has somehow mutated and is now very very contagious. This seems highly highly unlikely. A lot more people on that ship would be infected if that were the case.
How Does This Likely Play Out, Then?
Officials need to track down everyone who was on that ship, as well as their intimate contacts, and assess them for symptoms. Then, depending on a variety of circumstances, including whether any mild symptoms are present, they need to ask them to isolate for an extended period of time. This disease has an extended incubation period, lasting up to 8 weeks. And while transmission during incubation is very unlikely, it is possible during the mild symptomatic phase (like fatigue).
How Worried Should the Public Be?
It’s good that the public is aware of this outbreak and are learning about new diseases. It’s good that they’re also learning about those floating petri dishes called cruise ships. (Sorry, cruise ship industry, I lost a lot of money on the stock market when I gambled you guys would recover strongly from COVID. I’m still bitter.)
But, as I said, hantavirus is not COVID or Measles. It is not airborne in the sense of the word that most people understand. It won’t blaze through the population via person-to-person transmission. A high case-fatality ratio is scary…. if you get the disease. But it is very unlikely that you will get the disease, especially if you live in a city.
So, at this moment in history, on a scale of 0–10, I would advise the Canadian public to be 0.5 worried. Be aware that the disease exists, and of its parameters, but go about your life and let public health do its job.
As with all things in science, this is based on what is currently known. So, as I like to add to articles like this… all of this is true until further notice.
Raywat Deonandan is an epidemiologist and full professor at the Faculty of health Sciences at the University of Ottawa, as well as an award-winning author. This article was originally published in its entirety on Medium and on https://blog.deonandan.com on May 7, 2026.