90-Second Read: Hantavirus outbreak isn't another Covid pandemic – but experts say it's testing U.S. readiness

Unlike Covid, measles or the flu, the specific Andes strain of Hantavirus in the outbreak does not spread easily between people, making the risk of widespread spillover to the public low. While experts say the CDC appears to have the Hantavirus outbreak under control, some warn that the situation exposed cracks in the nation's public health infrastructure that could carry greater consequences in the face of a more contagious pathogen. The risk of this Hantavirus to the general public remains low, according to the WHO public health experts. The World Health Organization reported 11 cases linked to the outbreak as of Tuesday, nine of which it confirmed, including three deaths.

More cases could emerge in the coming weeks because Hantavirus has a long incubation period, experts said. Cases of Hantavirus disease are rare in the U.S.: From 1993 to 2023, 890 cases were reported, most of them in Western states, CDC data shows. The Andes strain of the virus seen in the outbreak, and found in South America, is the only Hantavirus that can spread from human to human. Hantavirus is primarily transmitted to humans through contact with infected wild rodents, especially through inhaling airborne particles from their urine, droppings, or saliva.

Treatments specifically for Hantavirus are still years away: Shares of Moderna rallied around 12% on Friday after it confirmed it was conducting early research on a potential vaccine to protect against Hantavirus. That's largely because Hantavirus does not spread as easily as other viruses like Covid do. Debbink said that's unlike Covid, which "spread pretty efficiently without a very long exposure." Hantavirus is not considered airborne because it does not linger in the air to infect others in the same way that respiratory viruses like Covid, the flu and measles do. Neil Maniar, a public health professor at Northeastern University, said the response to Hantavirus stands in stark contrast to 2020, when the CDC worked closely with international partners during Covid.

Hantavirus has an incubation period of one-to-six weeks after exposure, which means that more cases will likely crop up, said Debbink. While the CDC is now working with the WHO, experts say the Trump administration's decision to sever ties with the international health body is detrimental to the U.S.'s ability to respond to future outbreaks. WHO investigators believe the outbreak stemmed from a Dutch couple on board the MV Hondius cruise ship who later died from their infections.