The hantavirus outbreak grew to 11 cases on Tuesday, after a French woman became infected while aboard a cruise ship and is now being treated with an artificial lung in Paris and a Spanish passenger tested positive after departing the ship.

The World Health Organization (WHO) confirmed nine of the 11 cases. A Dutch couple has been confirmed dead after what health officials believe was exposure to the virus while visiting South America. The death of a German national is suspected to be caused by hantavirus.

“We expect more cases given the dynamics of spread on a ship and the virus’ incubation period,” the WHO said in a statement on the social platform X. “At the moment, there is no sign that we are seeing the start of a larger outbreak. Passengers and crew are being followed up in their countries, where WHO recommends a 42-day quarantine at home or in a facility starting from day of departure from the ship.”

WHO Director General Tedros Adhanom Ghebreyesus said there is no sign that the outbreak will grow, but noted that the situation “could change, and given the long incubation period of the virus, it’s possible we might see more cases in the coming weeks.”

Dr. Xavier Lescure, an infectious disease specialist at Bichat Hospital, told The Associated Press that the French passenger hospitalized in Paris has a severe form of the virus, which caused life-threatening heart and lung problems. Lescure said the artificial lung is “the final stage of supportive care.”

The Spanish passenger who tested positive for the virus is quarantined in a military hospital in Madrid, along with 13 other Spaniards who have tested negative.

Oceanwide Expeditions, which operates the cruise ship MV Hondius, stated on Wednesday that 27 people remain onboard, along with 25 crew members and two medical staffers. None have shown hantavirus symptoms, with the two medical staffers regularly monitoring all onboard.

Argentina’s Ministry of Health on Tuesday said they will dispatch a team of scientific experts to investigate the origin of the outbreak, as the MV Hondius departed the country on April 1, the AP reported.

Health officials noted that the Dutch couple took part in a bird-watching tour that stopped at a garbage dump and they may have been exposed to infected rats. The team that will be dispatched is expected to investigate the garbage dump.

Hantavirus generally spreads by rodents, but can be transmitted between humans in close contact. The virus’s incubation period can last about six weeks.

Seventeen Americans and one British national exposed to hantavirus on the cruise ship are quarantined either in Nebraska or Georgia while health officials monitor them for symptoms. Most have not shown symptoms of hantavirus, though one person tested positive without being symptomatic while another had mild symptoms but did not test positive.

U.S. health officials have said that the risk to the public is low compared to the risks brought on by COVID-19 ahead of the 2020 pandemic.

“This is not the next COVID, but it is a serious infectious disease,” Maria Van Kerkhove, director of epidemic and pandemic preparedness at the WHO, said last week. “Most people will never be exposed to this.”

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