At least three passengers on the Dutch cruise ship MV Hondius in the Atlantic Ocean have died from a respiratory infection, likely caused by the hantavirus. Two of the deceased are Dutch nationals, a spokesperson for the Ministry of Foreign Affairs confirmed to NOS.

The shipping company Oceanwides Expeditions spoke of a “serious medical situation” on board the ship. “During this voyage, three passengers have passed away. In addition, one passenger is currently being treated in intensive care in Johannesburg, and two crew members on board require urgent medical care.”

The deceased Dutch are a 70-year-old man, who died on board, and a 69-year-old woman who was transferred to a hospital in Johannesburg, South Africa, where she succumbed to the illness, according to information received by NOS. No information is available about the third passenger who died.

Three other people on board the ship have also fallen ill: a 69-year-old British passenger and two crew members. The Briton has been transferred to intensive care in Johannesburg, the World Health Organization (WHO) confirmed.

This man has tested positive for the hantavirus, and the WHO expects all the other cases to be this virus too. The WHO speaks of one confirmed and five possible infections with hantavirus.

The Hondius was en route from Ushuaia in Argentina to Cape Verde and is currently anchored off the coast of Praia, the capital of Cape Verde.

The Cape Verdean authorities have not granted permission for the two sick crew members to disembark, the shipping company said. Local health officials have been on board to examine the two. “They are yet to make a decision regarding the transfer of these individuals into medical care in Cape Verde.”

According to the shipping company, the Dutch government promised to lead efforts to bring the two sick crew members to the Netherlands. The WHO is also helping.

“WHO is facilitating coordination between member states and the ship’s operators for medical evacuation of two symptomatic passengers, as well as full public health risk assessment and support to the remaining passengers on board,” the WHO said to the South African news site Daily Maverick.

Hantavirus typically spreads to humans through rodents, such as rats and mice, when their droppings and urine become airborne. For example, when people sweep out an area with rat droppings. In rare cases, the virus can spread between humans.

The illness caused by the virus starts with flu-like symptoms, including fever and abdominal pain, and can lead to heart and lung failure. According to the U.S. Centers for Disease Control, around 40% of human hantavirus infections result in death. There are no specific medicines to treat hantavirus, so treatment focuses on symptom management and supportive care.

The Hondius departed from Ushuaia on March 20 for a 46-day trip. The ship has room for 170 passengers, 58 crew members, and 13 guides. According to the Ministry of Foreign Affairs, there were at least 10 Dutch nationals on board.