Hantavirus At Sea: Will It Plunge Us into a New Pandemic?

“An outbreak of hantavirus onboard the cruise ship MV Hondius has thrown a spotlight on the rare but deadly infection and the lack of options for treatment and prevention.”

Mohana Basu, Nature News, May 8, 2026

“This is not the next COVID, but it is a serious infectious disease.”

Maria Van Kerkhove, PhD, the World Health Organization’s director of epidemic and pandemic preparedness and prevention

In April 2025, the rare hantavirus made headlines when actor Gene Hackman’s wife died of hantavirus pulmonary syndrome—a severe and life-threatening respiratory infection. Now hantavirus is in the news again as a deadly outbreak that unfolded on the luxury polar cruise ship MV Hondius. This outbreak of hantavirus infection has captured an enormous amount of attention worldwide and is the basis of this week’s Germ Gems post.

What are hantaviruses (a recap)? Orthohantavirus is a genus of viruses that includes all hantaviruses. Hantaviruses form a family of RNA viruses. There are over 50 recognized species within the Hantaviridae family, 24 of which are known to cause disease in humans. (Dr. Ho-Wang Lee, a Korean virologist is credited with the discovery of Hantavirus in 1976.)

There are two main groups of hantaviruses: Old World hantaviruses and New World hantaviruses. Old World hantaviruses, found in Africa, Asia, and Europe, typically cause hemorrhagic fever with renal syndrome (HFRS). HFRS has a mortality rate that ranges from 1-15% depending on the specific hantavirus strain and region.

The New World hantaviruses, mainly the Andes virus (South America) and the Sin Nombre virus (North America), cause hantavirus pulmonary syndrome (HPS), a severe and potentially deadly disease that affects the lungs. It has a mortality rate ranging from 30% to 50%.

Hantaviruses are carried by rodents, particularly rats, mice and voles. In North America, the western deer mouse is responsible for transmitting the Sin Nombre virus. In South America where Andes virus is the most common cause of HPS, the long-tailed pygmy mouse is the most common animal reservoir.

Transmission of the virus to humans occurs mainly through inhalation of aerosols that contain saliva, urine, or feces of infected rodents. Transmission can also occur, however, through contaminated food, or bites and scratches from infected rodents. The Andes virus is the only strain of hantavirus shown conclusively to be transmitted by person-to-person contact.

Symptoms of HPS and treatment. The incubation period for HPS is usually about 1–8 weeks after exposure, with most cases occurring roughly 2–4 weeks after inhaling aerosolized virus particles from infected rodent urine, droppings, or saliva. The illness typically progresses through two phases: the Early Phase and the Cardiopulmonary Phase.

The Early Phase lasts about 3–6 days and often resembles a bad viral flu. Some people develop dizziness and a cough early on.  Other common symptoms include:

• Fever and chills

• Severe muscle aches, especially in the thighs, hips, and back

• Fatigue

• Headache

• Nausea, vomiting, abdominal pain, or diarrhea

  
  

The Cardiopulmonary Phase is the dangerous stage and can develop rapidly — sometimes within hours after the initial flu-like illness begins improving. Symptoms include:

• Cough

• Shortness of breath

• Rapid breathing

• Low blood pressure

• Fluid leaking into the lungs (pulmonary edema)

  
  

There is no specific treatment for hantavirus infections. Patients can deteriorate very quickly and may require intensive care or mechanical ventilation.

Hantavirus outbreak on a cruise ship. Cruise ships have experienced outbreaks from a surprisingly wide range of pathogens, most commonly norovirus and other viruses, including SARS-CoV-2, the cause of COVID-19. Most notably, the Diamond Princess was quarantined off the coast of Japan in February 2020 at the beginning of the pandemic.

Hantavirus infections are, however, rare. According to the World Health Organization (WHO), “ In 2025 … , in the Region of the Americas, eight countries reported 229 cases and 59 deaths…” (https://wwww.who.int/emergencies/disease-outbreak-new/item/2026-DON599). Outbreaks of hantavirus infections on a cruise ship are even rarer; this is the first time that there has been an outbreak of hantavirus on a cruise ship.

Hantavirus typically spreads when humans come into contact with the saliva, urine, or feces of infected rodents. The Andes virus is the only type of hantavirus known to be capable of limited human-to-human transmission , resulting in HPS. Cases have been reported, however, in community settings involving close personal contact. According to the WHO, it now appears that the Andes virus is the cause of this outbreak. (As yet, no evidence has shown that the ship had a rodent infestation.)

The first cases of hantavirus infection on the MV Hondias were two married Dutch nationals. The husband, a 70-year-old ornithologist, died on board, while his wife, a 69-year-old, was evacuated to South Africa, where she died in a Johannesburg hospital. It was reported that this couple had been bird-watching in South America and even visited a landfill four miles outside the city of Ushuaia, Argentina, prior to boarding the ship. (This landfill is a pilgrimage point for birdwatchers from all over the world in search of the white-throated caracara, aka Darwin’s caracara.)  It is hypothesized that the couple could have become infected with the Andes virus while bird watching, boarded the ship where they spread the virus to other passengers.

To date, three passengers have died and five others have become ill.  At least five cases were confirmed by lab testing to be caused by a hantavirus—most likely the rare Andes version. On Sunday, May 10, 2026, the ship docked in Tenerife’s Port of Granadilla in the Canary Islands where passengers disembarked for medical screening and repatriation. According to reports, the disembarking passengers had no immediate symptoms among them upon arrival.

But one of the five French passengers evacuated from the ship developed symptoms on the flight to Paris and was hospitalized. She tested positive for hantavirus and her condition worsened overnight. Of the 17 American passengers evacuated from the ship, health officials reported that one tested positive for the virus but was not showing any symptoms.

Nonetheless, health authorities, including the WHO and the Centers for Disease Control and Prevention (CDC) emphasized that the risk to the public of acquiring HPS is low. They noted that hantavirus does not easily spread from person-to-person and their focus will be on monitoring those who were exposed to the virus on the ship.

Is the Andes virus outbreak the start of the next pandemic. The WHO has stated this outbreak of hantavirus infection is a serious infectious disease, but it is not the beginning of a pandemic (that is, it’s not a worldwide infection). (Woodward, J., “Hantavirus outbreak will not cause a covid-style pandemic, says WHO,” New Scientist, May 7, 2026). While it is reassuring that the WHO is confident there is no reason to worry about the Andes virus igniting the next pandemic, other scientific and public health authorities aren’t quite so sure. ( Kovac, A., “A dangerous experiment is playing out on a cruise ship with hantavirus,” Scientific American, May 6, 2026).

Alison Kell, a virologist at the University of New Mexico,  said, “Biology can always surprise.” While Kell doesn’t think that the passengers on this cruise ship are likely to cause a global incident “because there are so limited cases, there are more limited opportunities for mutation and subsequent spread,” she is “not going to discount the possibility that that could happen.”

Off center. The CDC and other U.S. health public health and medical research organizations, like the National Institutes of Health (NIH), were center stage with the WHO throughout the COVID-19 pandemic. A striking difference between the response to the unfolding of the COVID-19 pandemic and this current outbreak is the relative absence of the CDC.

The apparent lack of engagement of these U.S. institutions in the current Andes virus outbreak isn’t surprising, given the drastic cuts in funding and turmoil at the CDC and NIH. Rather than reports of their constructive involvement, there has been a slew of articles highlighting the problems these institutions are facing. (Kovac, A., “Trump administration cut funding to study hantavirus, the virus behind the deadly cruise ship outbreak,” Scientific American, May 7, 2026; Mandavilli, A., “Hantavirus Response Shows How Trump Cuts Compromised U.S. Preparedness,” New York Times, May 7, 2026).

While this administration appears to have lost interest in the study of hantaviruses, it hasn’t lost its interest in military engagement.  And, the U.S. military has long wanted a hantavirus vaccine.

Hantaviruses are rodent-borne and pose a threat to our troops on the ground. Jay Hooper, a virologist at the U.S. Army Medical Research Institute of Infectious Diseases in Fredrick Maryland, has been working for more than three decades to develop a vaccine against several strains of hantavirus, including the Andes virus. But, as Dr. Hooper recently said: “Right now, we are pushing from the research side, but there is no strong external pull, so progress is slower than it could be. It’s frustrating—like pushing a rock up a hill for years.” (Basu, M ., “There is no vaccine for deadly hantavirus, but this scientist is working on one,” Nature News, May 8, 2026).

It would be ironic if scientists with the U.S. military lead the way to employment of the first hantavirus vaccine. I, for one, am cheering them on in their war on hantaviruses.