Three passengers have died and three others are being treated in a suspected hantavirus outbreak aboard a cruise ship in the Atlantic Ocean, health officials confirm.

The rodent-borne illness was confirmed in one case and is suspected in five others, the World Health Organization said Sunday. Investigations aboard the MV Hondius, traveling from Argentina to Cape Verde, are ongoing. Two of the deceased were identified as a Dutch couple, a man aged 70 and a woman aged 69. The man died on arrival on the island of St. Helena; the woman was evacuated to South Africa, where she died in a Johannesburg hospital. A third passenger, a German national, died on May 2; the cause has not yet been established. Two crew members currently on board have acute respiratory symptoms. Oceanwide Expeditions, the ship's operator, said 149 people representing 23 nationalities are on board. Strict precautionary measures, including isolation and hygiene protocols, are in place. Hantavirus is mainly spread by contact with rodents or their droppings. The WHO says investigations and sequencing of the virus are ongoing.