You’ve likely heard about the Andes virus, a type of hantavirus, which has been in the news lately after an outbreak on the MV Hondius cruise ship.

Washington State Department of Health (DOH) announced last week 6 people in Washington are being monitored for possible exposure to this outbreak. None are in Pierce County, and no cases of Andes virus have been reported in Washington.

While we believe the risk to people in Pierce County is minimal, we are keeping a close eye on this. We will continue to coordinate with DOH and other local partners as needed.

We’ve also heard a few questions recently from the community. Here are a few of those and some answers to help keep you up to date.

What are hantaviruses?

Hantaviruses are a group of viruses that can cause a severe and potentially deadly disease that mostly affects the lungs. People typically get infected with hantaviruses through exposure to wild rodents. You can get infected if you’re exposed to rodent urine, droppings, or saliva. You don’t need to have direct physical contact with a rodent to get infected. 

There are many types of hantaviruses. The Andes virus, which is the type found in the cruise ship outbreak, is the only one known to spread person-to-person. And even that strain does not spread as easily as more familiar viruses like seasonal influenza and COVID-19.

A different hantavirus is typically found in Washington. Deer mice can carry a type of hantavirus called Sin Nombre virus that is not known to spread person-to-person.

Typically, somewhere between 1 and 5 people in Washington are found to be infected with Sin Nombre virus each year.

What is the risk to the public?

The risk of Andes virus spreading in Washington is very low. However, it’s important to remember that prompt, coordinated public health action, in partnership with the people impacted, is what keeps the risk low. We need to have a coordinated public health system at all levels—local, state, and federal —as well as strong international partnerships, to respond effectively to threats like this.

Centers for Disease Control and Prevention (CDC) is working with international partners and state and local health departments to ensure public health agencies identify and monitor anyone exposed to Andes virus.

What happened with the cruise ship outbreak?

World Health Organization (WHO), CDC, and other countries are responding to an outbreak of Andes virus that started on the MV Hondius cruise ship. So far, we know of 11 people infected with Andes virus related to the outbreak.  

It can take up to 8 weeks after exposure to some hantaviruses for a person to develop symptoms. CDC recommends 42 days of monitoring after exposure to Andes virus, so the number of cases might grow.

People who might have been exposed are being monitored in multiple states, including Washington, and in other countries. 

How many people from Washington are being monitored?

DOH confirmed on May 15 that 6 people in the state are being monitored for Andes virus as possible exposures related to the cruise ship outbreak.

One King County resident was on the cruise ship and is quarantined at the National Quarantine Unit in Omaha, Nebraska.

Three other King County residents and 2 Eastern Washington residents might have been exposed on airplanes. They are isolating at home and will continue to be monitored.

Chelan-Douglas Health District also announced last week a case of Sim Nombre virus in a resident there. This is a different type of hantavirus and is not related to the cruise ship outbreak. They believe the person contracted it locally from a rodent.

How does the Andes virus spread? Why don’t you think this will lead to a big outbreak?

This is an important and complex question. When we think about different communicable diseases, one piece is the route of transmission. Some diseases spread only through direct contact with bodily fluids. Others can spread through what we call respiratory transmission (breathing and coughing). And some can spread through contaminated objects. To make it more complicated, some diseases can spread through multiple routes.

Then, for a given route of transmission, some diseases are more contagious than others. Based on prior outbreak investigations, we know the Andes virus can spread through respiratory transmission (breathing and coughing). But it doesn’t spread as easily as some other more familiar viruses like seasonal influenza and COVID-19.

This likely explains why we haven’t seen more cases from the cruise ship, despite the close quarters. This, along with prior investigations of Andes virus outbreaks, gives us confidence that the current public health measures should control this outbreak.

Different people with the same infection can also be more or less contagious. So, one person with Andes virus might not infect anyone else. Another might infect multiple people. The same is true for many other communicable diseases. The environments people are in also impact spread. The virus is more likely to spread when lots of people are packed together, like on a cruise ship or at a large party.

What should I do to protect myself?

Again, the risk to the public from the Andes virus is very low. CDC is performing contact tracing to identify people who may have been exposed as part of the cruise ship outbreak. For everyone else, there is minimal risk. I personally am not doing anything differently for myself or my family because of the Andes virus outbreak.

To protect yourself from hantaviruses more generally, you should continue to be careful around wild rodents and their waste. Avoid contact with rodent urine, droppings, saliva, and nesting materials. If mice or rats are in or around your home, it’s important to clean up after them safely. It’s essential to use wet cleaning and disinfection methods, and avoid sweeping or vacuuming so that you do not stir up viruses and then breathe them in.

If you have questions or concerns about hantavirus or other public health issues, you can always contact us directly.