Hantavirus, a rare but deadly virus carried by rodents, has killed three people and infected at least eight amid an ongoing outbreak on a cruise ship, prompting concerns about a possible pandemic and comparisons to COVID-19. While hantavirus is dangerous, all of the experts TODAY.com spoke with s tress that this outbreak situation is not similar to COVID-19, both due to the type of virus involved and ongoing containment efforts. “While this is a serious incident, (the World Health Organization) assesses the public health risk as low,” WHO chief Dr. Tedros Adhanom Ghebreyesus said in a press briefing on May 7. The MV Hondius had been stuck off the coast of Cabo Verde while officials scrambled to find a port to accept the hantavirus-stricken ship. The vessel is now heading to the Canary Islands, where it will dock in three to four days. In the meantime, officials are investigating how the ultra-rare virus made its way onto the luxury cruise ship and spread among passengers. Hantaviruses are a group viruses that can cause severe disease and death in humans. They’re not new, but outbreaks of hantavirus are very uncommon, Dr. Carla McWilliams, chair of the division of infectious diseases at the Cleveland Clinic in Florida, tells TODAY.com. Additionally, the strain of the virus involved in the cruise ship outbreak is even more uncommon, according to experts. Here’s what to know about the outbreak: 2026 hantavirus cruise ship outbreak On May 4, the WHO confirmed a cluster of hantavirus cases among passengers on the MV Hondius. Among the nearly 150 people aboard, eight suspected or confirmed cases of hantavirus have been identified so far, including three deaths. Three of the sick passengers have been medically evacuated to the Netherlands. One patient is critically ill and being treated in an intensive care unit in South Africa, where laboratory testing first confirmed the cruise ship outbreak was hantavirus. The newest case was identified in Switzerland in a man who left the Hondius voyage early and flew home, before the outbreak was identified. The cruise originally departed from Ushuaia, Argentina, on April 1 and made stops in Antarctica and several remote islands in the South Atlantic. It was in the waters of St. Helena island when passengers began falling ill and the first person died. On April 24, some 30 passengers disembarked in St. Helena after the death onboard, about a week before hantavirus was detected, cruise operator Oceanwide Expeditions said in a statement. These include several passengers from the United States. Health May 7 Cruise ship hantavirus outbreak sparks international effort to track passengers Health May 7 What is the Andes virus? Hantavirus linked to outbreak is most deadly strain Health May 6 3 sick passengers evacuated from hantavirus-hit cruise ship as new case confirmed Authorities in Georgia, Arizona, California, Texas and Virginia have confirmed they are monitoring residents who where on the ship and have since returned home. So far, none are showing symptoms, NBC News reported. As officials race to investigate the deadly outbreak, the WHO announced that the virus may have spread from person-to-person through a rare strain called the Andes virus. What is the Andes strain of hantavirus? At least 20 strains of hantavirus are known to cause disease in humans, Kari Moore Debbink, Ph.D, a professor of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health, tells TODAY.com. Most hantaviruses spread to people through contact with infected mice and rats or their feces, urine or saliva, often by inhaling aerosolized droppings, per the U.S. Centers for Disease Control and Prevention. “That’s the normal route in almost all cases,” says Debbink. Andes hantavirus, which is found in South America, mainly in Argentina and Chile, is unique in that it’s the only species known to cause human-to-human transmission, Dr. Mara Jana Broadhurst, pathologist and member of College of American Pathologists’ Microbiology Committee, tells TODAY.com. It spreads primarily to humans from the pygmy rice rat, but can also transmit between people through close, prolonged contact. “The precise mechanism of transmission between people has not been definitively established,” says Broadhurst, adding that Andes virus has been detected in blood, saliva, urine and semen. Only a small number of cases of the Andes strain involving clear human-to-human transmission have been documented. “These are mostly cases in people who were either living together or health care workers treating sick people,” Debbink adds. The cruise ship departed from Southern Argentina, where the Andes strain is endemic. Sequencing of samples from at least one patient confirmed the Andes strain, the WHO said. “Our assumption is (people) were infected off the boat and then joined the cruise,” Maria Van Kerkhove, epidemiologist and WHO technical advisor, said at a press briefing on May 5. “We do believe that there may be some human-to-human transmission that’s happening among the really close contacts,” Van Kerkhove added. However, it’s unclear how exactly each passenger was exposed. “I think part of the reason why this is novel is because it looks like there’s possibly human-to-human transmission beyond an isolated case or a small family outbreak,” Debbink says. The WHO’s investigation is ongoing. What is the risk to the public? While hantavirus is dangerous, experts say the general public doesn’t need to worry. Based on available information, the WHO said it currently assesses the risk to the global population from this hantavirus outbreak to be low. In a May 7 statement, the CDC also said that “at this time, the risk to the American public is extremely low. We urge all Americans aboard the ship to follow the guidance of health officials as we work to bring you home safely.” Debbink agrees: “Historically with the Andes virus, it’s spread between people in close proximity, so the risk of this transmitting more widely is pretty low.” In the past, the Andes strain hasn’t caused widespread outbreaks involving human-to-human transmission. One of the largest documented Andes virus outbreaks occurred in 2018 in Patagonia, Argentina and resulted in 34 cases and 11 deaths. There’s no reason to believe that the Andes virus has mutated into a more transmissible variant, Dr. Ashish Jha, a senior fellow at Harvard University’s Kennedy School, said on TODAY on May 7. The current cluster could result in additional cases among cruise passengers, Broadhurst notes, and secondary transmission among their close contacts is possible, but the risk of widespread transmission remains low. The WHO is working closely with the cruise staff, health authorities from countries involved and airlines to conduct contact tracing for passengers who left the ship early. No additional passengers, beyond the eight cases already identified, have reported feeling sick with hantavirus symptoms, Tedros said in the May 7 briefing. Due to the long incubation period, officials will continue to closely monitor everyone who was exposed on the ship. “Personally, I’m not worried. There’s been a very swift and prompt response to all of this, so hopefully the public feels reassured that there’s a plan in place,” says McWilliams. After the cruise ship docks in the Canary Islands, there will be a full outbreak investigation and disinfection process, NBC News reported. All passengers will be screened before going home and anyone who shows symptoms will be isolated, the WHO said. While the situation aboard seems terrifying, some passengers are painting a calmer picture. “People are taking the situation seriously but without any panic, trying to keep social distancing and wearing masks to be safe,” travel blogger Kasem Hato, said in a statement sent to NBC News. Will the hantavirus cause a pandemic, like COVID? If you’re wondering if hantavirus will become the next COVID, the answer from experts is no. “I don’t think people need to be terrified that this is all of a sudden going to start a pandemic. I would be absolutely shocked if that happened,” says Debbink. “This is not a COVID situation. I think they’re going to be able to contain the cases,” she adds. SARS-CoV-2, the virus that causes COVID, spreads very efficiently between people through respiratory droplets, Broadhurst notes. The Andes hantavirus behaves very differently. “It does not spread easily between people,” Broadhurst adds. In a press briefing on May 7, WHO officials reassured the public that they expect the current outbreak to be contained. Andes strain hantavirus symptoms Hantavirus can cause two distinct types of disease, depending on the strain, says Debbink. The Andes strain, along with other hantaviruses in the Americas, cause hantavirus pulmonary syndrome (HPS), a severe and often fatal respiratory illness, says Broadhurst. The incubation period is long, says Debbink. Symptoms of HCPS can take one to eight weeks to appear after exposure. Early symptoms of HPS include: Fever Chills Fatigue Muscle aches Headache Diarrhea, vomiting or abdominal pain After four to 10 days, these flu-like HPS symptoms progress to: Coughing fits Breathing difficulties Fluid in the lungs Respiratory failure “The fatality rate of HPS is 30-40%,” says Debbink. There is no specific treatment or cure for HPS, other than supportive care. The sick passengers aboard the Hondius mostly reported flu-like illness and gastrointestinal symptoms, per the WHO. Some remained mild, and others progressed rapidly to respiratory distress or pneumonia. Hantaviruses found in Europe, Asia and Africa cause a different disease, hemorrhagic fever with renal syndrome (HFRS). HFRS often starts with similar flu-like symptoms but progresses to internal bleeding and kidney failure — it’s more common than HPS, but the mortality rate is lower (less than 15%), says Debbink. How to reduce the risk of hantavirus There aren’t any special precautions the general public needs to take to protect against the Andes strain, the experts note. “This isn’t something people need to be worried about being exposed to. I wouldn’t cancel a cruise,” says Debbink. Most people will never be exposed to this virus, the experts note. However, you can reduce your risk of contracting all hantaviruses by minimizing your exposure to wild rodents, especially species known to carry hantavirus. In the U.S., the main culprit is the deer mouse, per the CDC. People usually get hantavirus from inhaling aerosolized particles from feces, urine or saliva, Debbink points out. Always seal holes and gaps in the home where rodents can enter or nest. When cleaning up droppings, avoid vacuuming or sweeping. Instead, wipe them up with a wet paper towel and a bleach solution. This story first appeared on TODAY.com. 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