Health officials are responding to a rare rodent-borne illness after a cruise ship outbreak of hantavirus left three passengers dead and sickened others, and global health experts stressed that the chance of spread beyond the affected cluster remains very low. The World Health Organization said most people will never be exposed to hantavirus, because it does not easily spread between people. Even so, officials are taking additional precautions for travelers as investigators work to determine how the cluster formed.
“This is not the next COVID, but it is a serious infectious disease,” Maria Van Kerkhove, the World Health Organization’s director of epidemic and pandemic preparedness, said. She added, “Most people will never be exposed to this.”
The AP reported that the outbreak involves a hantavirus type called the Andes virus, which health officials have continued to monitor for possible person-to-person transmission in rare circumstances. Paul Hunter, a professor of medicine at the University of East Anglia and an expert in the epidemiology of infectious disease, said hantavirus can be spread from contaminated aerosol vapor. Health officials typically describe the outbreak as a “cluster,” and they have used the term “outbreak” for a higher-than-expected number of cases in a population.
Health officials and experts said hantaviruses exist worldwide and spread mainly through contact with rodents. People are typically exposed when they inhale contaminated residue from rodent droppings that becomes airborne, particularly when enclosed spaces are disturbed or cleaned with poor ventilation, such as cabins or sheds. Scientists are still working to understand the mechanisms behind the Andes virus’s potential rare ability to spread between people, and Jeanne Marrazzo, chief executive officer of the Infectious Diseases Society of America, said experts suspect people could be infectious when they have symptoms and that transmission could occur through small liquid particles when infected people talk, cough or sneeze.
In the Americas, hantavirus infections have been relatively uncommon, and the World Health Organization reported that in 2025, eight countries in the Americas had documented 229 cases and 59 deaths. The AP reported that Argentina’s health ministry said hantavirus led to 28 deaths nationwide last year and, on Tuesday, reported 101 hantavirus infections since June 2025—roughly double the caseload recorded over the same period the previous year. In the United States, federal health officials began tracking the virus after a 1993 outbreak in the Four Corners region, which is where Arizona, Colorado, New Mexico and Utah meet.
Experts said the illness can become life-threatening and can present differently depending on which type causes infection. Symptoms can begin with flu-like complaints, including fever, chills, muscle aches and sometimes a headache. Symptoms of hantavirus pulmonary syndrome typically appear between one and eight weeks after exposure, and as the infection progresses patients might experience chest tightness as the lungs fill with fluid. The other hantavirus-related syndrome—hemorrhagic fever with renal syndrome—usually develops within a week or two and can cause bleeding, high fever and kidney failure. The AP reported that hantavirus pulmonary syndrome is fatal in about 35% of infected people, while hemorrhagic fever with renal syndrome’s death rate ranges from 1% to 15% of patients, according to the CDC.
Investigators are continuing detailed work to determine how the cruise ship outbreak began, including potential exposure locations outside the ship. The AP reported that investigators in Argentina suspect the cases were initially contracted during a birdwatching trip in Ushuaia, at the country’s southern tip, two officials told AP, while local officials said the virus had not previously been detected in the province.
On treatment and prevention, experts said there is no specific cure or targeted therapy, but early medical attention can improve survival odds. Steven Bradfute, an associate professor and associate director of the Center for Global Health at the University of New Mexico Health Sciences Center, which specializes in hantavirus research, said the virus can be very serious in the Americas but is also quite rare, and that less research has historically been driven by funding priorities. He said, “In the Americas, hantavirus infection is very serious, but it’s also quite rare,” adding that it meant “less research” for a time, though he said interest in funding has increased.
Public health guidance focused on avoiding rodents and their droppings. Experts said the best way to reduce risk is to minimize contact with rodents and their droppings, use protective gloves and a bleach solution for cleanup, and avoid sweeping or vacuuming that can kick particles into the air.
Correction note: None.
Associated Press journalists Mike Stobbe and Randy Herschaft in New York and Isabel Debre in Buenos Aires, Argentina, contributed.