90-Second Read: Hantavirus can have a long incubation period. Here's what that means

As international health authorities continue to contend with the outbreak that has sickened at least 9, including three deaths, the long incubation period of the virus poses a challenge for quarantine measures. Hantaviruses have relatively long incubation periods, according to the Centers for Disease Control and Prevention (CDC), taking between 1 and 8 weeks for symptoms to appear. That incubation period means that we can see cases again coming up in the next few days, perhaps even next week. Americans aboard the cruise ship at the center of a deadly Hantavirus outbreak were headed to quarantine on Monday, May 11, after they were evacuated back to the United States.

The current Hantavirus cases are a little more complex to track than more common diseases because it's rarer. Olivier Le Polan, unit head of epidemiology and analytics for response at the World Health Organization, told reporters on Monday, May 11, that it is tracking a 3 to 6-week incubation period, with most people expected to show symptoms by three weeks post-exposure. Passengers who go home will still be subject to a monitoring period, which states like New York have identified as 42 days, in line with WHO recommendations. Knowing the incubation period of a disease is important for doctors and scientists because it tells them how long it takes for someone to get sick after they contract an illness.

Hantavirus is typically transmitted to people through contact with rodents' urine, feces or saliva. An "incubation period" refers to the time between a person being exposed to a pathogen, such as a virus, and when they begin exhibiting symptoms. More specifically, the CDC estimates symptoms of Hantavirus pulmonary syndrome (HPS) appear between 1 and 8 weeks after exposure, and symptoms of hemorrhagic fever with renal syndrome (HFRS) appear within 1 to 2 weeks; however, symptoms can rarely take up to 8 weeks. Hantavirus is primarily spread when people come in contact with urine, droppings and saliva from rats, according to the CDC.

Experts know less about Hantaviruses and associated illnesses, especially the Andes virus, and how it may spread in the U.S., than something like the flu, which they see often. It's important to remember that Hantaviruses do not spread like COVID-19 or the common cold and generally require very close, extended contact, such as being confined to a cruise ship. How long will it take for sick or potentially sick people to be "cleared?" When will we know just how many Americans actually caught the virus?