A hantavirus outbreak aboard an expedition ship in the South Atlantic has killed at least three people and sickened several others, prompting health officials to monitor disembarked passengers across multiple countries.
The Dutch-flagged vessel MV Hondius departed southern Argentina on April 1 carrying nearly 150 passengers and crew from 23 countries, including 18 Americans. The outbreak is now confirmed as hantavirus, a pathogen that some rodents carry that can infect humans in rare, but often deadly, instances.
We spoke with Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health, about what makes this outbreak unusual and what the public should understand about the virus.
Normally, hantavirus doesn't spread from person to person. What makes this strain different?
Nuzzo: The Andes virus [ANDV] strain is a species of hantavirus that mostly circulates in Latin America —Argentina and Chile in particular. It is different from the hantavirus strain that, for instance, occurs in the southwest of the United States.
The Andes strain also tends to be a little bit more severe.
What also makes this strain different is that we have seen limited person-to-person transmission. Usually, it's among people with very close, prolonged contact.
How do health experts think it spread on the MV Hondius?
It seems like the first case may have been someone who was traveling in Argentina before getting on the boat, and then a person they were traveling with subsequently became ill and died. Then it possibly spread to others on the boat.
The thinking is that the other infections on the boat happened person-to-person. These people are in a small space together and have probably had a lot of opportunity to interact with each other and touch common surfaces, so that's the working hypothesis for how it likely spread, but I don't think we know for sure at this point. That’s because we don't know the connection between the people to be able to say exactly how it happened, like if they actually had extended contact with each other or not.
At the same time, I don't think we expect to see much more onward transmission outside of people who’ve already been exposed on the ship if the returned travelers go into quarantine or isolation.
What makes cruise ships vulnerable to outbreaks?
Well, an important thing to realize when it comes to this specific event is that this isn’t the big traditional cruise ship people think of: it's really an expedition vessel. It's carrying people who are exploring and going on adventures, which makes a big difference because it’s full of a lot of healthy, active people rather than the full range of people that might be on a cruise ship.
It’s also a smaller number of people than the bigger ships that carry thousands of people and are very notorious for outbreaks because you have tons of people, tons of common surfaces, tons of opportunity to breathe on each other.
I would say there's some of that opportunity on this vessel, but I'm a little bit worried that people have been too quick to dismiss this as just another ‘cruise ship outbreak’ and not consider what might be somewhat unusual about what we're seeing with this strain of hantavirus.
How dangerous is hantavirus?
This is a pretty deadly virus. It can kill about a third or more of people infected. That said, it's a rare infection—not a lot of people get it. As far as symptoms go, so far patients have had fevers, gastrointestinal symptoms and some respiratory symptoms. They can also get pneumonia, breathing difficulties and shock. Treatment is not clear since there are no standard treatments. I think doctors are trying to figure out on the fly how to manage these patients.
What happens next for passengers who have left the ship?
Procedures are different for each country, but basically passengers are being tested and then sent to quarantine or isolation facilities, depending on their condition. Quarantine if they've been exposed, but it’s not known that they're sick. Isolation is for those who’ve been infected.
In the U.S., some symptomatic passengers are being treated at specialized biocontainment units, including at Emory University Hospital in Atlanta, while many exposed passengers are quarantined at the National Quarantine Unit at the University of Nebraska Medical Center.
Because this virus has such a long incubation period—roughly one to eight weeks before they show symptoms—we could be talking about keeping them for an extended period.
Could there be undetected cases?
Given the fact that this happened on a ship and we know most of the people on the ship, I'm reasonably confident they know most people who have been exposed. Some of the challenges, of course, are the people who traveled on the vessel, disembarked and then may have traveled from there. They’re trying to contact people who may have been on the flights with them or in close proximity with them. It's possible there are undetected cases, but I'm not quite as worried as I would be if this just showed up in a city or a community because we generally have an accounting of who was on the ship and where they went.
Why are people criticizing the U.S. Centers for Disease Control and Prevention’s response?
I know the CDC has been working behind the scenes, particularly in terms of the repatriation of Americans who are on the ship. My understanding is they also have been in contact with local health departments about the outbreak and what they're doing, but none of that has really been made public and that is a deep mistake. When U.S. health officials have spoken on the outbreak, they have tended to speak overconfidently about how this virus is transmitted. They've said that it requires close, sustained contact from a symptomatic person. Though the limited data we have on past cases suggest that transmission is most common that way, these data are too few to support such definitive conclusions. We can't rule out the possibility of transmission before symptoms or from less than close, sustained contact.
A comparison is the European CDC. Around that same time, they published a technical document that described the virus as well as the threat that it poses. We really haven't seen that type of deep dive analysis from the U.S. CDC, despite its very great technical capacities.
We also haven't heard enough from the scientific experts at CDC. We've mainly heard from the political appointees and that's just not best practice. It doesn't engender confidence, doesn't help people understand how much of a threat this poses to Americans—even though it’s very low—or how much the average person should be concerned about it.
What do people misunderstand about this outbreak?
I think people are very understandably concerned that this could be the start of another COVID-like pandemic and, I think, that is unlikely to be the case. I'm not worried about a pandemic happening here.
What I am worried about is that the usual health response that we see out of the U.S. government isn't happening, and that this may be the virus telling us that it's gained some increased ability to infect and spread on a more limited basis. We don't have great medical tools to treat people who are infected. We don't have medical tools to prevent infection. Those are the kinds of research projects that we should be doing to try to stay ahead of not just this virus, but other deadly viruses. It doesn't have to be a pandemic to be a problem.
In this case, the fact that we have this virus that's acting in a way that's a bit confusing or a bit concerning—and we don't yet have all the answers—is the reason why we do research, and why we respond swiftly to try to stay ahead of it.
The Pandemic Center at Brown University School of Public Health is tracking developments in the hantavirus outbreak through the Outbreak Observatory’s outbreak data tracker and its weekly Tracking Report newsletter, which monitors major outbreaks in the United States and globally.