Now that more than 100 passengers aboard a hantavirus-stricken luxury cruise ship have been evacuated, with 18 Americans in biocontainment units in Nebraska and Georgia, health officials around the world are working to monitor more than two dozen individuals who left the cruise and anyone with whom they might have come in close contact.

So far, all of the 11 reported hantavirus cases are among passengers or crew on the ship, the World Health Organization’s director-general Tedros Adhanom Ghebreyesus said at a press conference in Madrid on Tuesday. That includes three deaths resulting from the virus.

Typically, hantaviruses are spread when contaminated rodent droppings and urine are stirred up in the air and breathed in. The strain identified on board the cruise ship, the MV Hondius, is known as the Andes virus, and is the only type known to transmit from person to person. While the virus can cause serious disease and carries a high fertility rate, health officials say the hantavirus outbreak is unlikely to become a global crisis like the Covid-19 pandemic.

“At the moment, there is no sign that we are seeing the start of a larger outbreak,” Ghebreyesus said, “but of course the situation could change and, given the long incubation period of the virus, it’s possible we might see more cases in the coming weeks.”

WIRED spoke with Nicole Iovine, chief epidemiologist and an infectious disease expert at the University of Florida Health, about how the Andes virus spreads and whether it's likely to spark another pandemic.

This interview has been edited for brevity and clarity.

WIRED: One of the things that is probably top of mind for most people is how similar is the Andes virus to SARS-Cov-2, and how infectious is it?

Nicole Iovine: It is not similar at all to SARS-Cov-2. This outbreak on the cruise ship is not going to translate into a worldwide pandemic like Covid for a number of reasons. One of the reasons is that it is just not as infectious as Covid was. Covid infected our upper airways and also deep in our lungs. But the fact that it infected our upper airways meant that when we talked or sneezed or coughed, it was easily put out into the air and so it was easy to transmit. With the Andes virus, this virus actually infects very deep in the lungs. It doesn't typically infect the upper airways, so it's a lot harder for it to transmit from one person to another.

How would you know if you had the Andes virus? It seems like the symptoms are pretty nonspecific at first but progress quickly to serious disease.

People can start to get symptoms anywhere from about five days or so after exposure to as long as six weeks, which is again very different from Covid and another reason why hantavirus is of some concern but is not likely to cause a pandemic. It starts out with very generalized symptoms. You can develop a fever, headache, fatigue, muscle aches and pains. Those sorts of symptoms are what you would get if you had the flu or many other sorts of infections.

Is the Andes virus airborne?

Not exactly, because the way that it transmits into your lungs is if you have really close contact with someone for an appreciable amount of time. It's not something like measles, where if you're in a room and you have measles, somebody could come into that room two hours later and still contract measles. That's airborne, but hantavirus is not like that.

The most common way it's spread is through exposure to rodent droppings or urine. Let's say you're in a house, and you decide to do some spring cleaning in your basement, you'll stir up dust and microscopic particles that will contain the virus from the droppings and urine. But that doesn't mean it's airborne. It just means that you stirred up the dust that was containing the virus.

What does close, prolonged contact mean? Are we talking 60 minutes, several hours, or more?

To some extent, it depends on what you're doing. For example, the ship's doctor is positive for the hantavirus, but that's not a normal interaction. The doctor is going to be looking down the throat and listening to breathing, being really close up with that first patient. So it's not entirely surprising that he has developed the infection. Now if you're sitting down at the captain's table and having dinner on the cruise ship, is the person right directly next to you at risk? Possibly.

The other thing is, with any infectious disease, there are periods of greater and lesser infectiousness. We do know that for the hantavirus, the infectious period starts with symptoms, increases over a few days, and then will start to decline. If you're in a highly infectious period, then you need a shorter exposure to pass on the virus. Early on, when there's not as much virus, then you would need a much more prolonged exposure.

Can the virus spread without close contact with someone who has it? Are there other possible routes of transmission?

It's possible that you could contract it by touching a contaminated surface. That would also be if you're outside and you're gardening and there are rodent droppings and your hands get contaminated and you don't wash your hands effectively.

One of the elements here that makes this unique is that the initial spread of the virus happened on a cruise ship, which is a very confined space. What role does ventilation, or the lack of ventilation, play in this case?

A room with poor ventilation is going to allow greater transmission than, say, a standard hospital room, which has many air exchanges per hour. Being outside is definitely a much lower risk situation than being inside. There’s a lot of nuance here.

Does the average person have to worry about getting this virus?

No, definitely not. If you refer back to the New England Journal of Medicine paper from 2020 [that described an outbreak of Andes virus from late 2018 to early 2019], once they instituted containment measures, that's when the virus was no longer able to transmit and sustain the outbreak. Since we already know now what we're dealing with, and containment measures are in place, this is not going to have pandemic potential.

I worry about a lot of things but I'm not worried about this. I'm worried about measles outbreaks.