An outbreak of hantavirus aboard a cruise ship has killed three passengers and sickened an undisclosed number of others, a cluster of cases that has drawn heightened global health scrutiny because the specific strain involved — the Andes virus — is the only known member of the hantavirus family capable of rare person-to-person transmission. While the World Health Organization has moved quickly to assure the public that a pandemic scenario is not in the cards, the deaths have spotlighted a pathogen that, though difficult to catch, carries a fatality rate far higher than COVID-19 once infection takes hold.
“This is not the next COVID, but it is a serious infectious disease,” said Maria Van Kerkhove, director of epidemic and pandemic preparedness at the WHO. “Most people will never be exposed to this.”
Hantaviruses exist throughout the world and are spread primarily through contact with rodents — specifically their urine, saliva, and droppings. The virus typically infects people when contaminated material is disturbed and becomes airborne, creating a risk of inhalation. People are most often exposed around homes, cabins, or sheds, particularly when cleaning enclosed spaces with poor ventilation or exploring areas where mice have nested.
Detailed investigations into the cruise ship outbreak remain ongoing. Two officials told the Associated Press that investigators in Argentina suspect the cases were initially contracted during a birdwatching trip in Ushuaia, at the country’s southern tip, though officials in the province note the Andes virus has not previously been detected there. The investigations are working to pinpoint exactly how the virus moved from that remote environment onto the vessel.
Argentina has experienced a surge of hantavirus cases over the past year, with the nation’s health ministry reporting 101 infections since June 2025 — roughly double the number recorded during the same period a year earlier. The ministry said hantavirus led to 28 deaths nationwide last year. Many local public health researchers attribute the rising caseload to climate change, which may be altering rodent habitats and increasing the frequency of human encounters with infected animals.
The person-to-person transmission question sits at the center of the current public health response. Unlike COVID-19, which can spread from symptom-free carriers, hantavirus has never produced large-scale human-to-human outbreaks. “We haven’t had huge person-to-person spreads of hantavirus infection ever before, and there’s no reason to suspect a huge outbreak from this case at this point,” said 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.
Scientists are still working to understand the mechanism by which the Andes virus may transmit between people. Dr. Jeanne Marrazzo, chief executive officer of the Infectious Diseases Society of America, said researchers suspect infected people could be contagious when symptomatic, and that transmission may occur through small liquid particles expelled when a person talks, coughs, or sneezes. Still, the WHO has stated that any human-to-human spread would require “close and prolonged” contact.
Paul Hunter, a professor of medicine at the University of East Anglia and an expert on the epidemiology of infectious disease, told the AP that hantavirus can also be spread from contaminated aerosol vapor — a transmission pathway that underscores why public health experts caution against sweeping or vacuuming areas with rodent droppings.
Because of the Andes virus’s rare capacity for human transmission, health officials are taking extra precautions with passengers returning to their home countries from the affected cruise ship. The WHO reported that in 2025, eight countries within the Americas documented a combined 229 hantavirus cases and 59 deaths, figures that reflect the disease’s low incidence but high lethality.
An infection typically begins with symptoms that resemble the flu: fever, chills, muscle aches, and sometimes a headache. Symptoms of hantavirus pulmonary syndrome usually appear between one and eight weeks after exposure to an infected rodent. As the illness progresses, patients may experience tightness in the chest as the lungs fill with fluid. The other syndrome caused by hantavirus — hemorrhagic fever with renal syndrome — can produce bleeding, high fever, and kidney failure, usually developing within a week or two after exposure.
Death rates vary by which hantavirus causes the illness. Hantavirus pulmonary syndrome is fatal in about 35% of people infected, while the death rate for hemorrhagic fever with renal syndrome ranges from 1% to 15% of patients, according to the CDC. There is no specific treatment or cure, though early medical attention can increase the chance of survival.
In the United States, federal health officials began systematically tracking hantavirus after a 1993 outbreak in the Four Corners region, where Arizona, Colorado, New Mexico, and Utah meet. An astute physician with the Indian Health Service first noticed a pattern of deaths among young patients, leading to the identification of the virus. Most U.S. cases since have occurred in Western states, with New Mexico and Arizona serving as persistent hot spots — likely because the odds of mouse-human encounters are greater in rural areas.
The disease gained renewed public attention last year after Betsy Arakawa, the wife of late actor Gene Hackman, died from a hantavirus infection in New Mexico. The virus family itself is named for the Hantaan River in Korea, where the first member was discovered. That virus, the Hantaan virus, infected 3,000 soldiers during the Korean War in the 1950s, causing a disease called Korean hemorrhagic fever that killed 190 of them. The virus itself was not identified until more than two decades later.
Public health experts say the most effective protection is minimizing contact with rodents and their droppings. They recommend using protective gloves and a bleach solution for cleaning up rodent waste, and caution against sweeping or vacuuming in areas where droppings are present — actions that can launch virus particles into the air.
“In the Americas, hantavirus infection is very serious, but it’s also quite rare,” Bradfute said. “And so for a time that probably led to less research into it because of funding priorities, but I know there’s been a lot of interest in funding hantavirus work of late.” Despite years of study, researchers have yet to answer many questions, including why the illness can be mild for some and severe for others, and how protective antibodies develop.