Three people who were aboard a cruise ship sailing the Atlantic Ocean have died of suspected infections of hantavirus, the World Health Organization said on Sunday, referring to a rare family of viruses carried by rodents.

One case of the infection was confirmed in a laboratory, the organization said in a statement. There are five additional suspected cases, it said.

Of the six people infected, three have died and one person was in intensive care in South Africa, it said.

Foster Mohale, a spokesman for the National Department of Health in South Africa, said passengers of an international cruise ship, MV Hondius, were in South African medical facilities “following serious health complications arising from undiagnosed severe acute respiratory infection.”

The MV Hondius, which was carrying about 150 passengers from various countries, left Ushuaia in Argentina about three weeks ago for the Canary Islands, stopping in mainland Antarctica, the Falkland Islands, South Georgia, Nightingale Island, Tristan, St. Helena, Ascension and Cape Verde, Mr. Mohale said.

The operator of the ship could not be immediately reached on Sunday.

One of the patients, a 70-year-old male passenger, became ill and was experiencing a fever, headache, abdominal pain and diarrhea, Mr. Mohale said.

The passenger died on arrival in St. Helena Island, he said, and his remains were awaiting repatriation to Netherlands.

The victim’s 69-year-old wife also became ill on board and collapsed at the O.R. Tambo International Airport in South Africa while trying to fly home to the Netherlands. She was taken to a health facility, where she died.

The third patient was a British national who became ill while the ship was traveling from St. Helena to Ascension Island and was transferred from a hospital in Ascension to a private South African health facility in Sandton.

His laboratory test results came back positive for hantavirus, Mr. Mohale said.

The department is working with the National Institute for Communicable Diseases and Gauteng Health authorities to conduct contact tracing, Mr. Mohale said.

“There is no need for the public to panic because only two patients from the cruise ship have been within our borders,” Mr. Mohale said, adding that the “World Health Organization is coordinating a multicountry response with all affected islands and countries to contain further spread of the disease.”

Hantavirus refers to a family of viruses that are carried by rodents. It is often transmitted to humans by inhaling particles of dried deer mouse droppings or urine.

At first, hantavirus causes flulike symptoms, including fever, chills, body aches and headaches. But as the disease progresses, respiratory symptoms develop and patients can experience shortness of breath and then lung or heart failure.

The disease made headlines last year after Betsy Arakawa, the wife of the actor Gene Hackman, died from the effects of the virus.

The Centers for Disease Control and Prevention reported 890 cases of hantavirus as of the end of 2023 since surveillance began in 1993.