Hantavirus explained: What to know as WHO suspects human-to-human spread
Health officials are scrutinizing the hantavirus after the World Health Organization (WHO) said it is investigating whether limited human‑to‑human transmission may have occurred during a deadly outbreak on a cruise ship, raising new questions about a disease long believed to spread almost exclusively from infected rodents.
Hantavirus is a family of viruses typically transmitted to humans through contact with rodent urine, droppings or saliva, most often by inhaling contaminated particles. Person‑to‑person spread is considered extremely uncommon, though it has been documented in rare cases involving the Andes strain in South America. In the current outbreak, which has been linked to a cruise ship off the coast of Cape Verde, WHO officials said transmission between close contacts cannot be ruled out, though they have emphasized that the overall risk to the broader public remains low and that investigations are ongoing.
The cluster, which has been tied to multiple deaths, has prompted an international investigation into how the infection spread. Hantavirus infections can begin with mild, flu‑like symptoms before rapidly progressing to severe respiratory failure, making early detection and intensive medical care critical. Investigators are working to determine how the virus spread among passengers and whether the strain involved could explain the unusual cluster of cases.
Which Cruise Has Hantavirus?
The current hantavirus outbreak under investigation is linked to the Dutch‑flagged expedition cruise ship MV Hondius, which was carrying 149 passengers and crew during a voyage through the South Atlantic. The ship departed Ushuaia, Argentina, on April 1, and traveled through remote regions including Antarctica, South Georgia, Tristan da Cunha, Saint Helena and Ascension Island, before becoming stranded near Cape Verde after multiple passengers fell seriously ill, a report from the WHO said.
As of Monday, the WHO reported seven confirmed or suspected cases of hantavirus among those onboard, including three deaths, one critically ill patient in intensive care, and several with milder symptoms. Two infections have been laboratory‑confirmed, while the remaining cases are considered probable and remain under investigation.
The outbreak is highly unusual, in part because no active rodent infestation has been identified on the ship, raising questions about whether exposure occurred before boarding or during the voyage. The agency has emphasized that the overall risk to the public remains low but has not ruled out limited human‑to‑human transmission while investigations continue.
Passengers on board should wash their hands frequently and self-isolate in their cabins until more information is available about the virus and how the patients contracted it. Dr. Michelle Harkins, chief of pulmonary, critical care and sleep medicine at University of New Mexico, encouraged passengers to monitor themselves for symptoms and wear a mask should they notice any.
As to who’s most at risk, Harkins said that severe outcomes can be influenced by how well a person’s immune system responds to the virus.
“Underlying medical conditions can increase the likelihood of having worse symptoms,” she told Newsweek. “The patients that have advanced medical problems may be at a higher risk of having severe outcomes, but it can occur in the pediatric population and adults.”
Harkins said she expects “more reliable information” to be available within the next 24 hours.
The names of the three people who have died have not yet been released, although a press release from the South Africa Department of Health identified the victims as a husband and wife, age 70 and 69, respectively, from the Netherlands, and a British man.
Newsweek reached out to the South Africa Department of Health by email for comment regarding the patients’ identities.
What Are the Symptoms of Hantavirus?
Hantavirus infection often begins with nonspecific, flu‑like symptoms, making early diagnosis difficult. According to the WHO and U.S. Centers for Disease Control and Prevention (CDC), patients typically experience fever, fatigue, muscle aches, headaches, nausea, vomiting, diarrhea and abdominal pain during the initial phase of illness.
Newsweek reached out to the CDC by email for comment.
In more severe cases, particularly those involving hantavirus pulmonary syndrome, symptoms can rapidly worsen after several days. Patients may develop shortness of breath, coughing, chest tightness and difficulty breathing as fluid builds up in the lungs, often progressing to acute respiratory distress syndrome and shock.
Health experts warn that the sudden deterioration can be deadly if not treated promptly.
Where Does Hantavirus Come From?
Hantaviruses are zoonotic viruses primarily carried by rodents, including mice and rats. Humans are most commonly infected through inhaling aerosolized particles from rodent urine, droppings or saliva, particularly when contaminated materials are disturbed during cleaning or in enclosed spaces such as cabins, sheds or storage areas.
Different hantavirus species circulate in different parts of the world and are associated with specific rodent hosts. In the United States, most cases are linked to deer mice, while in parts of South America, infections are often associated with the Andes virus, a strain that has been linked in rare circumstances to possible person‑to‑person transmission.
“The Andes virus, which circulates in Chile and Argentina, is the only hantavirus documented to transmit from person to person, and it is rare. The Hondius left from Ushuaia, in Argentine Patagonia, which is squarely within that virus’ range. That geography matters,” Dr. Tyler Evans, founder and CEO of Wellness Equity Alliance, told Newsweek. “It is the most plausible explanation for what we are seeing, and it is also the reason this outbreak should not cause panic among people who have no connection to that part of the world.”
Because hantavirus exposure typically occurs on land, experts have described the cruise ship outbreak as atypical. WHO officials have said it remains unclear whether those affected were exposed before boarding in Argentina, during shore excursions or through close contact with an infected passenger or crew member during the voyage.
Hantavirus Incubation Period: What We Know
The incubation period—the time between exposure and the onset of symptoms—for hantavirus is considered relatively long and variable. According to WHO officials, symptoms typically emerge between one and six weeks after infection, with some cases taking even longer to become apparent.
This extended incubation window has complicated efforts to pinpoint the source of the outbreak aboard the Hondius. WHO epidemiologists have said the timing of symptom onset in several cases suggests at least some patients may have been infected before boarding the ship, though this has not been confirmed.
The long incubation period means additional cases could still emerge, even among passengers who currently feel well. As a precaution, public health authorities have advised close monitoring of all exposed people and continued medical surveillance after disembarkation.
“In terms of severity, hantavirus infections can range from mild to life-threatening,” Alexander Ploss, co-director of the Global Health Program and a molecular biology professor at Princeton University, told Newsweek. “Case fatality rates vary substantially by geographic region and viral species, generally ranging from less than 1-15 percent in Europe and Asia to as high as 30-50 percent in the Americas. The fatalities reported in this outbreak fall within that upper range. This underscores the need for being vigilant.”
Is Hantavirus Curable?
“At present, there are no approved vaccines or specific antiviral treatments,” Ploss said. “Management therefore relies on early recognition and supportive care, ideally in a facility with full intensive care capabilities, which can significantly improve outcomes.”
Care is largely supportive, focusing on early hospitalization, oxygen therapy, careful fluid management and, in severe cases, mechanical ventilation and intensive care.
Outcomes depend heavily on how quickly patients receive treatment. Studies show that early recognition and rapid access to advanced supportive care significantly improve survival, particularly for patients who develop hantavirus pulmonary syndrome.
“For the general public, the overall risk remains low,” Ploss said. “Preventive measures focus on minimizing exposure to rodents and their excretions, as well as adhering to public health guidance, particularly in outbreak settings. Situations like a cruise ship and a plane [one of the cases flew to Johannesburg] require heightened awareness due to the potential for close-contact transmission, but they are not representative of everyday risk.”
