What Is Andes Hantavirus? Everything to Know About the Deadly Virus
At least 11 passengers aboard the MV Hondius cruise ship are reported to have contracted the Andes strain of hantavirus, while U.S. health officials continue monitoring additional passengers who may have been exposed.
Cruise ship Andes hantavirus outbreak leaves three dead as experts study possible human-to-human spread.
Among the 18 Americans who were on the ship and are currently in quarantine facilities in the United States, at least three are being closely observed for possible infection. Three passengers from the cruise have already died from the virus.
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Health experts say all recently confirmed cases involve people who had direct contact with infected individuals on board. However, growing concerns remain about whether the Andes strain may spread more easily than previously believed. The Andes strain is the only known hantavirus capable of person-to-person transmission.
For years, experts believed transmission occurred mainly through close contact with symptomatic individuals. Some researchers now believe the virus could spread under less prolonged exposure than earlier assumptions suggested.
“What we’re hearing now, including from the doctors who were on the ship, is that at least a few people contracted it without that long, prolonged exposure that we’ve always assumed,” Dr. Ashish Jha, a senior fellow at Harvard University’s Kennedy School, told NBC’s “TODAY” show on Monday.
According to Dr. Brendan Jackson, acting director of the high-consequence pathogens and pathology division at the Centers for Disease Control and Prevention, the crowded environment aboard the cruise ship appears central to the outbreak.
Cruise ships are often linked to infectious disease outbreaks because passengers spend extended periods together in confined spaces while frequently sharing high-touch areas, including buffets and other communal facilities.
“That is definitely different than how we live most of the time,” Jackson said.
Before the Hondius outbreak, hantavirus transmission on cruise ships had not been documented. The outbreak became widely known after three passengers were confirmed to have died from the Andes strain earlier this month.
Despite growing concern, Jackson emphasized there is currently no evidence that the virus itself has mutated to become more infectious.
Experts continue to stress that the overall risk of widespread transmission remains extremely low, though many unanswered questions about the virus still exist.
How Andes Hantavirus Spreads Between People
Of the dozens of hantavirus strains identified worldwide, only the Andes strain is known to spread from person to person. Officials say this strain infected at least nine passengers from the Hondius, while additional suspected cases are under investigation.
Jackson explained that the virus generally does not spread easily between humans.
“When it does, it typically involves household members that are doing things like sharing beds or sharing eating utensils or having contact with body fluids,” he said.
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Dr. David Fitter, head of the CDC’s Division of Global Migration Health, also emphasized the difficulty of transmission during a media briefing at Emory University Hospital in Atlanta, where two passengers remain under observation.
“This is very different than a respiratory virus. It’s very difficult to spread,” Fitter said.
Experts also noted that prolonged physical closeness could potentially increase the likelihood of transmission. Earlier Monday, Jackson explained at a briefing in Omaha that the CDC generally defines close exposure as remaining within six feet of another person for more than 15 minutes.
“There’s nothing magical about 6 feet. It’s not a force field, but it’s a rough number that gives us a sense of how close somebody has been,” he said. “It’s a fairly conservative approach given the evidence we have so far about how this virus has spread in the past.”
Most hantavirus infections occur after individuals inhale or ingest particles from rodent urine or droppings containing the virus. Experts estimate that only 2% to 5% of Andes strain cases result from person-to-person transmission.
Large-scale outbreaks involving the virus remain extremely uncommon.
One notable outbreak occurred in Epuyén, Argentina, where three infected individuals attended crowded social gatherings, including a birthday party. The incident eventually resulted in 34 cases and 11 deaths.
Researchers investigating the outbreak found that one infected individual likely transmitted the virus to another person seated roughly one to two meters away at a table. Another infection may have occurred during a brief greeting while crossing paths.
Can Hantavirus Spread Before Symptoms Appear?
Jackson stated that there is currently no documented evidence showing asymptomatic individuals spreading the virus before developing symptoms such as coughing or sneezing.
Still, experts caution that the possibility cannot be completely ruled out.
Dr. Rachael Lee, chief health care epidemiologist at the University of Alabama at Birmingham, said researchers still lack sufficient data about mild or undetected cases.
“What we don’t have good data on is how many people are potentially exposed and then just develop antibodies,” Lee said. “We don’t really know too much about transmission from one person to the next.”
Specialists say hantavirus behaves differently from highly contagious respiratory viruses like flu or Covid because it settles deeper within the lungs rather than concentrating in the upper airways.
“That’s one of the things that would limit the spread of the Andes virus,” said Dr. Nicole Iovine, chief epidemiologist and infectious disease expert at the University of Florida Health’s Shands Hospital, “because it’s not in your throat or your nose.”
The virus remains particularly dangerous because it can inflame blood vessels and severely limit oxygen flow in the body. Experts estimate hantavirus fatality rates can reach up to 50%.
Jackson said researchers are continuing to learn more as the outbreak develops.
“It’s important to remember that we’re very early in this outbreak,” he told NBC News. “The risk to the public is very, very low at this time, but that doesn’t mean we’re letting our guard down.”
