Maria Van Kerkhove, WHO"s chief of Epidemic and Pandemic Preparedness and Prevention, said that the outbreak is "not the start of a pandemic" and "not COVID."

　　DELAYED DETECTION COMPLICATES TRACING

　　The outbreak has revealed a complex chain of transmission across ships, flights, and multiple countries, raising the possibility of further cases in the coming weeks.

　　Argentine officials investigating the outbreak said the leading hypothesis is that a Dutch couple contracted the virus before boarding after visiting a landfill during a bird-watching outing in the city of Ushuaia, where rodents were likely present.

　　The first known patient -- the husband of the couple -- developed symptoms aboard the ship on April 6 and died before hantavirus was suspected, as the illness initially resembled other respiratory infections. His wife later disembarked at Saint Helena while symptomatic and died during a flight to Johannesburg, where infection was confirmed. The third fatal case was a separate female passenger aboard the ship who developed symptoms on April 28 and died on May 2, according to WHO.

　　WHO warned that more cases may emerge given an incubation period of up to six weeks, although no new symptomatic cases have been reported onboard.

　　French health authorities said a French citizen who never boarded the cruise ship is being monitored as a "contact case" after sharing a flight with an infected passenger.

　　The development suggests the transmission chain could expand from the confined cruise ship environment into commercial aviation, French media reported, making contact tracing significantly more challenging.