The vessel, operated by Oceanwide Expeditions, was carrying about 150 passengers and around 70 crew members when several people became ill. The World Health Organization said one hantavirus case has been confirmed, while other cases remain under investigation.
Among the dead are a 70-year-old Dutch man and his 69-year-old wife. A 69-year-old British passenger is reportedly in intensive care in Johannesburg, South Africa. Two crew members on board are also said to need urgent medical care.
The ship has been off the coast of Cape Verde, with the operator saying it is waiting for permission to disembark sick passengers. Health authorities are now working to determine how the virus may have spread on board.
Hantavirus is usually linked to exposure to infected rodents, especially through urine, droppings or contaminated dust. It can cause severe respiratory illness, but person-to-person transmission is considered rare for most hantavirus types.