The reported illnesses this spring initially looked like the spread of a typical stomach bug on a luxury ocean liner, but the situation quickly escalated to a fatal outbreak of hantavirus, a rare rodent-borne pathogen, leading to weekslong quarantines for the ship’s passengers and a global health alert.
But the outbreak is now over, the World Health Organization announced on Thursday. Overall, there were 12 confirmed cases and one probable case aboard the cruise ship, including three deaths.
The declaration was made after the final contact of a passenger completed a quarantine period and tested negative for the virus, said the health agency, which is part of the United Nations.
The announcement ended a three-month saga that had scientists scrambling to find the origins of a rare vector for hantavirus; crew members and passengers held captive on a luxury ship; and global health officials enforcing contact tracing and quarantine protocols.
The luxury cruise liner, MV Hondius, began its trip carrying 175 passengers and crew members from nearly two dozen countries as it left Ushuaia, an Argentine city, on April 1. The first passenger sickened by the virus died less than two weeks later.
The last reported case was on May 25, Tedros Adhanom Ghebreyesus, the director general of the W.H.O., said in making the announcement.
The passengers caught in the outbreak were to enjoy a leisurely journey aboard the state-of-the-art polar expedition ship from Argentina to remote islands in the southern Atlantic Ocean, including stops in mainland Antarctica, the Falkland Islands and Cape Verde.
Several passengers who boarded the ship were passionate bird watchers interested in the landfill in Ushuaia because it is a prime location to spot the white-throated caracara, a raptor bird. For a brief period, there was speculation that the landfill was the likeliest source of the contagion.
After the outbreak began, the ship was headed to Cape Verde, where government officials did not allow it to dock, saying that it was too small a country to handle the outbreak. The ship was refused entry in multiple countries, and the passengers and crew became isolated captives in the middle of the Atlantic Ocean.
Patient zero was a Dutch man, 69 years of age, who first showed vague, flulike symptoms on April 6, five days after the cruise began. He died on board on April 11.
His wife, also 69, became ill after leaving the ship with his body on April 24 on the island of St. Helena in the South Atlantic, where the ship was finally allowed to dock. She reported “gastrointestinal symptoms,” the W.H.O. said. She died on April 26 in Johannesburg, where she was going to take a flight home to the Netherlands.
About 30 people from at least 12 countries left the ship in St. Helena, a British territory. Two days after the second death linked to the virus, on April 28, a German woman had “fever and general malaise,” and then had symptoms of pneumonia, the W.H.O. said. She died aboard the ship on May 2.
The next day, after laboratory testing, the W.H.O. confirmed that the hantavirus was on the ship, attributing one of the infections to the virus.
While the ship was moored off the coast of Cape Verde, an archipelago in the Atlantic Ocean off West Africa, government and health officials around the world raced to find a way to evacuate the sick people onboard. By then, the hantavirus outbreak had been tied to seven people on the ship, according to the W.H.O.
The government of Spain allowed the ocean liner to dock on May 9 at Tenerife, one of the Canary Islands. It was nearly six weeks after the ship had left Argentina, and, during a two-day interval, all the remaining passengers were tested and disembarked.
By May 11, many of the passengers and some crew members were either on their way to their home countries, or had already arrived. Many of them, including 18 Americans, were quarantined when they arrived home.
On May 18, the Hondius arrived at the Port of Rotterdam, in the Netherlands, with only 27 passengers and crew members placed in a special quarantine area. After the ship was inspected and samples were collected, it was cleaned and disinfected.
Dr. Tedros said that over 650 contacts of people on the ship were identified, and that health officials in about three dozen countries and territories reached out to those contacts.
The W.H.O. said it believed the outbreak originated on land and was not an infestation from the multimillion-dollar ship. The agency identified the strain as the Andes subtype, which can be transmitted between people in close contact.
The Andes subtype caused the deaths of the two first patients who traveled on the ship, the agency said. It is endemic in three provinces across Argentina’s Patagonia, with several cases reported there every year, according to the health authorities.
There are no targeted treatments for hantaviruses, which are typically carried by rodents, and no widely available vaccines.
But Dr. Tedros expressed optimism that one could arrive.
“We are also coordinating a study involving 21 countries to understand how the disease develops,” he said, “which will support the development of diagnostics, therapeutics and vaccines for future outbreaks.”
