A deadly hantavirus outbreak aboard a cruise ship in the Atlantic has raised new questions about how the rare, rodent-borne disease may have spread.
The outbreak has left at least three people dead with five additional suspected cases, as the World Health Organization investigates.
Although hantavirus is usually transmitted through contact with infected rodent droppings, experts say the close quarters of the vessel could have amplified the risk.
The virus is typically found in rodent saliva, urine and feces, becoming airborne near contaminated surfaces, according to Dr. Carrie Horn, chief medical officer at National Jewish Health in Colorado.
While other viruses like COVID-19 also enter through inhalation, they originate from another person’s respiratory tract, she noted. In contrast, person-to-person hantavirus transmission is very unlikely.
“It most often gets into the air when the rodent nest is disturbed, such as when being cleaned up. It is then inhaled into the lungs,” Horn told Fox News Digital.
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It is “technically possible” that the virus could be aerosolized (spread into the air) through a ventilation system, the doctor said.
“It is also possible that if a rodent infestation occurred and passengers tried to clean something up, they could have become infected,” Horn added. “This is very low risk, but possible. It is also possible that they were exposed off of the ship.”
Another possibility, she said, is eating contaminated food could cause disease, although that would be less likely than breathing it in.
Dr. Jacob Glanville, CEO of Centivax, a San Francisco biotechnology company, reiterated that hantavirus could potentially spread on a cruise ship under certain conditions.
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“It’s possible, either because there are infected mice on the ship and people are being infected from those mice, or because of human-to-human contact transmission, which the Andes strain has been previously demonstrated to be capable of,” he told Fox News Digital.
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He also pointed out that the ship had stopped in South America and that the lethality appeared more consistent with strains from the Americas.
Glanville cautioned that until it can be ruled out that a more transmissible strain is involved, removing passengers from the ship could pose risks.
“Otherwise, there is a small but high-consequence risk of creating a lethal international outbreak,” he warned.
Historically, hantavirus has been “far less transmissible” than COVID-19, the doctor said. “Unless that changes with a new mutant strain, the risk remains very low to the public.”
Dr. Marc Siegel, Fox News senior medical analyst, confirmed that hantavirus almost always requires a rodent vector to spread, though rare cases can occur through contact with contaminated materials or bites.
The experts agreed that the risk to the wider public is low. Siegel reiterated that people should “not be very concerned.”
Glanville noted that it’s still unclear whether the cluster came from human-to-human transmission – “although given a potential Andes strain origin, that is a risk.”
“Even if it’s an Andes strain, historically transmission human-to-human is inefficient,” he told Fox News Digital. “However, it is always possible that a novel mutant can arise that is able to propagate more easily between humans.”
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If any new transmission cases are found from contacts who were not on the ship, the situation would become much more concerning, according to Glanville.
“Hantavirus can be 30% to 50% lethal, has a long silent incubation period of one to six weeks, and has the potential for droplet transmission,” he warned.
Experts say symptoms typically begin with fever, muscle aches, fatigue and headaches, followed by cough, shortness of breath and, in severe cases, fluid buildup in the lungs.
These symptoms can mimic flu-like illness, according to Horn.
“From there, it can progress to having trouble breathing, needing oxygen and requiring hospitalization,” she told Fox News Digital. “Some people can have gastrointestinal issues as well, such as vomiting and diarrhea.”
In extreme cases, the virus can cause severe lung and cardiovascular disease, with a fatality rate of 30% to 50%.
“It can affect the heart, lungs and kidneys, causing all of them not to work appropriately,” Horn told Fox News Digital. “Infected people can have trouble maintaining their oxygen levels to the point of needing to be on a ventilator or to get external oxygenation support.”
Because the virus is rare, specific risk factors are not well-known, but overall health can influence outcomes, the expert added. Age may also be a factor, as those who died on the cruise ship were elderly.
Experts advise avoiding areas where rodents may be present — particularly dusty or enclosed spaces with signs of infestation — and not disturbing nests or droppings. If cleaning such areas, wearing a filtered mask can help reduce risk.
Travelers should also avoid contact with rodents and contaminated materials, while taking basic precautions like handwashing, disinfecting surfaces and maintaining good overall health.
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“This is a very unusual situation,” Horn added, emphasizing that hantavirus poses a very low risk to the public — especially for those not on the affected ship.
