ANTARCTICA — The World Health Organization is investigating a rare hantavirus outbreak aboard the cruise ship MV Hondius during a week-long Antarctic voyage. Officials are examining whether the virus spread between people on the vessel.

The MV Hondius departed Ushuaia, Argentina, on April 1 and visited Antarctica and several isolated islands, according to the WHO. The ship's route runs from Ushuaia to Antarctica and then north along the coast of Africa.

Dr. Maria Van Kerkhove, director of epidemic and pandemic preparedness at the WHO, said the agency is investigating possible human-to-human transmission of hantavirus on the MV Hondius. Hantavirus typically transmits through inhalation of contaminated rodent droppings.

Officials suspect that the first infected person likely contracted hantavirus before boarding and that there are no rats on board. Investigators have found no evidence of contamination from the ship.

The outbreak occurred as tourism to Antarctica has grown rapidly. In 2024, more than 80,000 tourists landed on Antarctica and 36,000 observed from ships, according to the International Association of Antarctica Tour Operators. Tourism to the continent has grown tenfold over the past 30 years, according to the International Union of Concerned Scientists, and researchers at the University of Tasmania estimate that annual visits could triple or quadruple to over 400,000 in the next decade.

Most Antarctic expeditions visit the Antarctic Peninsula. Some tourists travel to the region as a form of last chance tourism because they know the landscape is rapidly changing.

Disease transmission has previously affected the region and the cruise industry. Migratory birds transported avian influenza from South America to Antarctica in recent years, according to the U.S. Centers for Disease Control and Prevention. That outbreak prompted the International Association of Antarctica Tour Operators and others to strengthen tourist conduct and hygiene rules. Crews and passengers on Antarctic voyages clean shoes and equipment using vacuums, disinfectants, and brushes to remove bugs, feathers, seeds, and microbe-carrying dirt.

Cruise ships have also experienced norovirus outbreaks that can spread quickly in close quarters. Separately, in 2020, the Diamond Princess cruise ship experienced a COVID-19 outbreak that spread among passengers and crew.