A hantavirus outbreak has emerged aboard a cruise ship traveling through the South Atlantic, leading to a multinational health response. The vessel, which departed from Ushuaia, Argentina in early April 2026, carried fewer than 150 passengers and crew. Initially, passengers exhibited symptoms resembling routine infections, but concerns grew as some developed severe respiratory issues. To date, at least three deaths have been reported, and laboratory tests have confirmed hantavirus infections in at least two individuals, with more suspected cases under investigation. Health authorities from 12 countries, including the United States, Canada, and Germany, are involved in the response, focusing on identifying potential sources of exposure and patterns of infection. The cruise route included visits to ecologically sensitive regions, such as Antarctica and remote Atlantic islands, raising concerns about the outbreak's origins and implications for public health.