What to Know About the Hantavirus Outbreak on an Atlantic Cruise Ship

Officials are investigating an outbreak of hantavirus, a rare family of viruses carried by rodents, aboard a cruise ship sailing the Atlantic Ocean.

Three passengers who were aboard the MV Hondius have died, and five other people have been sickened after showing symptoms of the rare disease, according to the World Health Organization. One of the people who died was confirmed to have the virus, as well as two people who were ill.

The vessel left the coast of West Africa on Wednesday and headed north toward the Canary Islands, where it will dock and evacuate passengers, according to the authorities.

One person who was confirmed to have the virus was in critical condition and receiving intensive care in South Africa. In Switzerland, a man with another confirmed case of the virus was receiving treatment at a hospital in Zurich. A Dutch woman who died in South Africa was also confirmed to have had the virus.

Among the people who showed symptoms were two crew members, including the ship’s doctor. Two evacuated patients arrived in the Netherlands on Wednesday, where they were receiving medical attention, according to Oceanwide Expeditions, the vessel’s operator. Another evacuated patient was on a different plane, which was delayed, the company said.

Here’s what to know:

Three people have died, but the risk to the wider public is low.

The W.H.O. has said that there was no need for panic.

“Based on the current information, including how hantavirus spreads, W.H.O. assesses the risk to the global population from this event as low,” the agency said on social media on Tuesday.

The three people who died were a Dutch couple and a German citizen, according to Oceanwide.

The first fatality was a 70-year-old Dutch man who died on board the ship on April 11. Nearly two weeks later, on April 24, his body was taken off the ship at St. Helena, a British island territory in the South Atlantic, to be repatriated to the Netherlands, Oceanwide said. The man had experienced a fever, a headache, abdominal pain and diarrhea.

The man’s 69-year-old wife became ill after disembarking from the ship with his body, and collapsed at O.R. Tambo International Airport in Johannesburg, South Africa, before a planned flight home to the Netherlands. She was taken to a health facility, where she died. Oceanwide said on Monday that she was confirmed to have had a variant of the hantavirus.

Then, on May 2, a German passenger died aboard the ship, according to Oceanwide, which said the cause of death was still unclear.

A British citizen fell ill during the ship’s voyage between St. Helena and Ascension Island, another British territory in the South Atlantic, and was in intensive care in Johannesburg. His laboratory results came back positive for hantavirus, said Foster Mohale, a spokesman for the National Department of Health in South Africa. The person’s condition “was improving,” the W.H.O. said on Tuesday.

The vessel was carrying around 150 people, including 88 passengers and 61 crew members, according to Oceanwide.

There were some Americans on the ship who have already returned home. Two Georgia residents are being monitored by the state’s Department of Public Health, it said in a statement. They “are currently in good health and show no signs of infection,” the department said.

The California Department of Public Health was notified by the C.D.C. that California residents had been on the MV Hondius as well, said Robert Barsanti, a spokesman for the department. The agency is assisting local health authorities with monitoring, he said. “There is no information that the California residents are ill or infected,” Mr. Barsanti said. “At this time, the risk to public health in California is low.”

The Arizona Department of Health Services received notification that one resident was a passenger on the ship, according to a spokeswoman. “This individual is not symptomatic and is being monitored,” she added.

The virus may have been transmitted between people.

Hantavirus is typically contracted when people breathe in particles of dried droppings or urine from infected rodents.

It is uncommon for the disease to spread among people, according to the Centers for Disease Control and Prevention. But the W.H.O. said on Tuesday that some of those who had fallen ill may have been infected through human-to-human transmission, cautioning that the vessel still needed to undergo a full investigation and that such transmissions were rare.

“We do know that some of the cases had very close contact with each other, and certainly human-to-human transmission can’t be ruled out,” Maria Van Kerkhove, the W.H.O.’s head of epidemic and pandemic preparedness, said.

Investigators in South Africa and Switzerland have confirmed that the cases involve the Andes virus, which is primarily found in South America and is the only hantavirus known to spread between people.

The W.H.O. also said it believed that the Dutch couple, who joined the cruise in Argentina, had been infected with the hantavirus before boarding the ship.

The hantavirus is uncommon but dangerous.

The disease is rare, but it can result in severe illness and death for those who are infected. The C.D.C. cited a case fatality rate of up to 15 percent in Asia and Europe and up to 50 percent in the Americas.

Early symptoms include fever, chills, body aches and headaches. As the illness progresses, it can cause shortness of breath and, in severe instances, lung or heart failure. There is no specific treatment for the virus, but symptoms can be treated with intubation, oxygen therapy, fluid replacement and medication, according to the C.D.C.

Several studies have linked the risk of hantavirus disease to environmental factors such as increased rainfall, which boosts rodent populations. Conversely, droughts can also raise infection risk by driving rodents to seek food in human habitats.

From 1993 to 2022, there were 864 recorded cases of the disease in the United States, according to the C.D.C. Last year, Betsy Arakawa, wife of the actor Gene Hackman, died from the effects of the virus.

The ship had departed from Argentina and was headed for the Canary Islands.

The Dutch-registered MV Hondius departed Ushuaia, Argentina, for the Canary Islands, said Mr. Mohale, the South African health official. The Argentine health authorities in the southern province of Tierra del Fuego, from which the ship departed on April 1, said there were no known cases of hantavirus in the area.

Cape Verde was a scheduled stop on the cruise’s itinerary, Mr. Mohale said. Other planned stops included Antarctica, the Falkland Islands, South Georgia Island, Nightingale Island, Tristan da Cunha, St. Helena and Ascension, he added.