By Brenda Goodman, CNN
(CNN) — In 2018, health authorities in southern Argentina were racing, trying to understand what had caused nearly three dozen people in the tiny village of Epuyen to fall gravely ill. By the end of the outbreak, 11 of them had died.
Their illness, which caused many to be admitted to intensive care for pneumonia and severe breathing problems, was caused by the Andes virus, a strain of rodent-carried hantavirus capable of being transmitted from person to person. It is the same virus that’s believed to have sickened eight passengers traveling on the MV Hondius cruise ship, which is sailing to a port in the Canary Islands.
Before the Epuyen outbreak, very little was known about the Andes strain, said Dr. Gustavo Palacios, a microbiologist at the Icahn School of Medicine at Mount Sinai in New York.
“There is very limited experience handling this virus,” said Palacios, who was the director of the Center for Genome Sciences at the US Army Medical Research Institute of Infectious Diseases when he helped piece together how the virus moved from person to person. The study of the outbreak was published in 2020 in the New England Journal of Medicine.
“Probably we are having less than – I don’t know, I’m giving you a number, just for a ballpark number – 300 cases in history,” Palacios said, adding that he is also part of a group of experts advising on the ongoing cruise ship outbreak.
Based on their investigation of the Epuyen outbreak, which involved three separate superspreader events – where a single person passed the infection to several others – Palacios said the window for transmission of the Andes virus appears to be short, about a day. People are at their peak of infectiousness on the day they develop a fever.
But the study also found that the virus could be passed relatively easily during this window, after periods of only brief proximity to someone else.
The researchers were able to show that the first patient, a 68-year-old man who attended a birthday party with about 100 other people, infected someone else after being in contact with them for only a few moments, on the way to the restroom.
Tracing the path of a killer
The index case — the first documented case — in the Epuyen outbreak is believed to have been infected near his home. In Argentina, the Andes virus is carried by long-tailed pygmy rice rats, which are common in agricultural areas and can live around houses.
Around the world, including in the US Southwest, rodents are known to harbor hantaviruses. Humans are typically infected through contact with their urine, feces or saliva, sometimes when the virus becomes aerosolized during cleaning.
Most recently, hantavirus made news in the US in 2025 after an autopsy determined that Betsy Arakawa, the wife of actor Gene Hackman, had died of the virus.
In most cases, hantaviruses result in what’s called a dead-end infection: A human gets infected after contact with animal droppings but doesn’t pass it on to anyone else.
Andes virus is an exception, however. It can spread between people, giving it the potential to spark outbreaks.
While the World Health Organization says the threat posed from the current outbreak on the cruise ship Hondius is low, WHO has classified hantaviruses as emerging priority pathogens with high potential to spark international public health emergencies because of how serious these infections can be. Hantavirus infection can be lethal in Read more