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 ship, the MV Hondius, have died, and five other people have shown symptoms of the rare disease, according to the World Health Organization. One of the people who died was confirmed to have the virus, as were four of the other people.

Health officials in several countries are testing people who have been on the ship or in close contact with those who were. The World Health Organization has said that the risk to the general population is low.

The vessel left the coast of West Africa on Wednesday with about 150 passengers and crew and was headed north toward the Canary Islands, where it was expected to anchor offshore and evacuate passengers.

Among the confirmed cases are a Dutch woman who died in South Africa; two British citizens; and a man hospitalized in Switzerland.

Here’s what to know:

There is not a major risk to the wider public.

The W.H.O. has said that it assesses the risk to the global population from the outbreak as low.

“This is not the start of an epidemic — this is not the start of a pandemic,” Dr. Maria Van Kerkhove, the W.H.O.’s head of epidemic and pandemic preparedness, told reporters in Geneva on Thursday.

A 69-year-old Dutch man died on board the Hondius, a Dutch-registered 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. 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 she collapsed at an airport in Johannesburg, South Africa, where she had briefly boarded a flight to the Netherlands. She was taken to a health facility, where she died.

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. He tested positive for hantavirus but his condition “was improving,” the W.H.O. said this week.

Among the people who showed symptoms were two crew members, including the ship’s doctor, and a German passenger who had been in close contact with one of those who died. They were evacuated to the Netherlands, where they were receiving medical attention, according to Oceanwide Expeditions, the vessel’s operator.

Health authorities in Britain said on Friday that a British citizen on Tristan da Cunha, another remote British territory in the South Atlantic, was a suspected case.

In Spain, health officials said on Friday that a woman was being monitored in a hospital in Alicante with coughing and other symptoms. The woman had been on the flight that was briefly boarded by the Dutch passenger who later died.

In France, eight people were being monitored after being identified as coming into contact with a cruise passenger who was positive for the virus during a flight from St. Helena to Johannesburg on April 25, the French health ministry said on Thursday.

American passengers who returned to the U.S. are being monitored.

Some of the 17 Americans who were on the ship have already returned home. Georgia health officials said two residents of the state were being monitored and “are currently in good health and show no signs of infection.”

Some California residents had been on board and were being monitored, though there was no information that they were ill, said Robert Barsanti, a spokesman for the California Department of Public Health.

The Arizona Department of Health Services received notification that one resident was a passenger on the ship, according to a spokeswoman, who said that the person was not sick and was being monitored.

In Texas, two residents are being monitored, according to the state department of health and human services.

One passenger on the ship was being monitored after returning home to Virginia, according to the state department of health.

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,” Dr. Kerkhove of the W.H.O. said.

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

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

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. Droughts can also raise infection risk by driving rodents to seek food in human habitats. From 1993 to 2023, the most recent year with available data, there were 890 recorded cases of the disease in the United States, according to the C.D.C. Last year, Betsy Arakawa, the wife of the actor Gene Hackman, died from the effects of the virus.

The ship is headed for the Canary Islands.

Medical flights helped three patients evacuate from the Hondius while it was near Cape Verde on Wednesday. The ship then began traveling toward the Canary Islands, a Spanish territory in the Atlantic Ocean. The vessel is expected to arrive on Sunday.

The ship will not dock at a port but will remain anchored offshore until the remaining passengers are transferred by boat to Tenerife for evacuation flights, the Canary Islands regional leader said on Thursday.

Mónica García, the Spanish health minister, said in a statement that passengers would be assessed on the ship and would disembark “with protective equipment, a specific health operation, and without contact with the population.”

There are currently no symptomatic people on the ship, according to the W.H.O.

Aurelien Breeden, Emma Bubola, Ceylan Yeğinsu, Lynsey Chutel, Alexandra E. Petri, John S.W. MacDonald, Rylee Kirk and Aimee Ortiz contributed reporting.