A deadly hantavirus outbreak aboard a cruise ship in the Atlantic Ocean has prompted global concern and an investigation by the World Health Organization.

At least three passengers have died, and five additional cases are suspected, raising questions about how the rodent-borne virus spread in such an environment.

Jake Rosmarin, a travel blogger on board the M/V Hondius, said he is thankful for the crew’s response and efforts to maintain safety as health officials assess the situation.

Hantavirus is generally transmitted through contact with droppings, urine, or saliva from infected rodents.

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Experts say the ship’s confined spaces may have increased the likelihood of exposure, though the disease rarely spreads between humans.

Dr. Carrie Horn, chief medical officer at National Jewish Health in Colorado, explained that the virus can become airborne when a rodent nest is disturbed, leading to inhalation of contaminated particles.

“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,” she said.

While airborne spread through ventilation is “technically possible,” Horn said such transmission is unlikely. She added that passengers may have been exposed while cleaning contaminated areas or potentially even off the ship.

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Eating tainted food, while possible, would be less likely than breathing in the virus, she noted.

Dr. Jacob Glanville, CEO of Centivax, a biotechnology company in San Francisco, said conditions aboard a cruise ship could allow hantavirus transmission under certain circumstances.

“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 said.

Glanville observed that the ship had recently stopped in South America, suggesting the strain’s severity may resemble those found in that region.

He cautioned against disembarking passengers before ruling out a more transmissible variant, warning of “a small but high-consequence risk of creating a lethal international outbreak.”

Despite those concerns, Glanville emphasized that hantavirus is historically “far less transmissible” than COVID-19. Unless a new mutant strain changes this pattern, he said, the broader public risk remains very low.

Dr. Marc Siegel, Fox News senior medical analyst, supported that assessment. He said most hantavirus cases require a rodent vector, though rare infections can arise from contact with contaminated items or bites. He stressed that the general public should “not be very concerned.”

Experts agree the possibility of human-to-human transmission is limited.

“Even if it’s an Andes strain, historically transmission human-to-human is inefficient,” Glanville said. However, he added that mutations could alter that risk and that experts are watching closely for any cases among contacts who were not aboard the ship.

Hantavirus infection can cause serious illness. Early symptoms often include fever, fatigue, muscle pain, and headaches before advancing to cough, difficulty breathing, and in severe cases, lung fluid buildup.

According to Dr. Horn, “From there, it can progress to having trouble breathing, needing oxygen and requiring hospitalization.”

The virus can damage the heart, lungs, and kidneys, sometimes leading to multi-organ failure. Fatality rates have ranged between 30 percent and 50 percent, depending on the strain and the patient’s health. Those who died aboard the cruise were elderly, which experts say may have influenced their outcomes.

Horn recommended avoiding spaces where rodents might be present, especially enclosed or dusty areas showing signs of infestation. She advised not disturbing nests or droppings and using a filtered mask during cleanup.

Travelers should also practice routine hygiene, including handwashing, disinfecting surfaces, and maintaining good health habits.

Calling the incident “a very unusual situation,” Horn repeated that hantavirus poses a very low risk to the public, particularly to those not aboard the affected vessel.

The World Health Organization continues to investigate the outbreak as health experts monitor passengers and potential contacts from the cruise. Officials said findings from the probe will determine whether the infections were confined to the vessel or stemmed from exposures elsewhere.