Hantavirus risk remains low, health officials say

Published 1:30 am Tuesday, May 26, 2026

Will hantavirus reach King County?

Recently, Public Health – Seattle & King County announced that four people from King County are being monitored for symptoms following potential exposure to the Andes strain of hantavirus. Read more here: tinyurl.com/PHSKC-hantavirus4.

One of them was a passenger on the MV Hondius cruise ship who is now being monitored at the national quarantine center in Nebraska. The remaining three people had low-risk exposures — they were passengers on a plane that also carried a symptomatic person before the infectious agent was identified as hantavirus. That passenger disembarked the plane before takeoff. According to Public Health, all four remain asymptomatic.

What do we know?

Hantaviruses are a group of viruses, primarily carried by wild rodents, that can cause severe disease in humans.

The Andes strain of hantavirus is found in South America and is the only strain known to spread from person to person. Because people were on a cruise together, this particular outbreak spread among a community of people from all over the world.

Rodents in the United States are not known to carry the Andes strain of hantavirus.

While experts don’t completely understand the Andes strain of hantavirus and its transmission, evidence from the MV Hondius cruise ship and prior outbreaks suggests that human-to-human transmission requires very close and prolonged contact with an infected person, and that the virus has a long incubation period, averaging 45 days.

In the Americas, hantaviruses may cause severe infection in people, with an approximately 30% mortality rate due to respiratory compromise and circulatory collapse.

Hantavirus infections are rare — typically, one to five cases are reported in Washington residents each year.

In Washington state, the deer mouse is the primary animal known to carry the virus. About 10% to 30% of deer mice are infected. Humans usually acquire it by inhaling droplets or dust particles from infected urine, droppings or saliva.

Not surprisingly, some people are wondering whether this is the start of a new pandemic. There are certainly some superficial similarities with the early stages of the COVID-19 pandemic, and they are worth acknowledging — public awareness of a virulent virus in a far-off place, uncertainty about how it is transmitted or what controls its virulence, and no known treatment or vaccine for protection.

But Public Health estimates the current risk to King County residents from the Andes strain to be extremely low: There are no known cases here, it does not appear to be highly infectious, exposed individuals are being closely monitored, and infected individuals do not appear to be able to transmit the virus before symptoms appear. While viruses can and do change, outbreaks of the Andes hantavirus strain in South America have tended to fizzle out before they became epidemic, for the reasons just mentioned.

It is worth noting how quickly and effectively the World Health Organization responded to this crisis. WHO was able to rapidly develop a plan to safely isolate cruise ship passengers and crew with symptoms, observe those with significant exposures, and repatriate for monitoring those with less significant exposures, like those from King County. Information has been shared rapidly across the globe, including with the U.S., which withdrew from WHO in 2025. The rapid response and transparency we’ve seen in the past month is a silver lining of the COVID-19 pandemic.

So what can we do?

Take precautions against the risk of contracting hantavirus infection. Wear an N95 mask or respirator and gloves before cleaning out your attic, basement, garage or any place rodents may have been present. Don’t move dry material with a broom or vacuum. First, air out the space, then wet down rodent-related areas with a 10% bleach solution — be sure the bleach is labeled “disinfecting.” After soaking everything for 10 minutes, remove all droppings and nest materials with a damp towel, and then mop or sponge the area with the 10% bleach solution. If you do vacuum, use a vacuum cleaner with a HEPA filter.

Read more about cleanup here: tinyurl.com/DOH-rodent-cleanup.

Stay informed about hantavirus and the current Andes outbreak at publichealthinsider.com, doh.wa.gov/newsroom and doh.wa.gov/you-and-your-family/illness-and-disease-z/hantavirus. Information in Spanish is available at doh.wa.gov/es/you-and-your-family-illness-and-disease-z/hantavirus.