The cruise ship hit by a deadly hantavirus outbreak arrived near Spain's Canary Islands on Sunday.
Health authorities from several countries began a large medical and evacuation effort to screen, isolate and repatriate nearly 150 passengers and crew.
The MV Hondius arrived near Granadilla Port in Tenerife around 5:30 a.m. local time (0430 GMT), escorted by a Civil Guard vessel, according to AFP journalists.
White tents lined the dock, and police secured part of the port before the operation began.
The ship departed Ushuaia, Argentina, on April 1 for a transatlantic cruise to Cape Verde. It will remain anchored offshore and not dock.
Passengers are brought to shore in groups of five by boat, screened by medical staff, and then taken by bus to the airport about six miles (9.65 kilometers) away for repatriation flights.
Six hantavirus cases have been confirmed on board, with two additional suspected cases, according to the World Health Organization (WHO).
Three passengers have died—a Dutch husband and wife and a German woman. Health officials said there are no remaining suspected cases on the ship.
Scientists have identified the outbreak as the Andes variant of hantavirus, the only type known to spread from person to person, usually through close contact.
The WHO said two passengers who later died had traveled through Argentina, Chile, and Uruguay before boarding.
"We classify everybody on board as what we call a high-risk contact," said Maria Van Kerkhove, WHO's director of epidemic and pandemic preparedness and prevention, speaking Saturday.
WHO Director-General Tedros Adhanom Ghebreyesus traveled to Spain on Saturday and tried to ease public concern in an open letter to the people of Tenerife.
“I need you to hear me clearly," he wrote. "This is not another COVID-19." After arriving in Tenerife, he told reporters he was confident the operation would succeed, saying: "Spain is ready and prepared."
Spanish nationals are among the first to be evacuated. Some will be taken to a military hospital in Madrid for quarantine, which will last one to two weeks based on medical advice. Seventeen US passengers will fly to the United States and be monitored at a special quarantine unit in Nebraska.
Spain's health and interior ministers said there would be "no contact" with the local population and that passengers would leave "by nationality groups."
The interior minister also said all areas passengers pass through would be sealed off, and a maritime exclusion zone would stay in place around the ship.
Dutch cruise operator Oceanwide Expeditions said "all guests and a limited number of crew members" were expected to start leaving the ship around 7 a.m. GMT.
"Once disembarked, they will be transferred immediately to their allocated aircraft," the company said.
Regional authorities did not allow the ship to dock. Officials said the only suitable time for the operation was during a brief period of good weather between Sunday and Monday.
Health authorities in several countries have been tracking passengers who left the ship before the outbreak was confirmed.
The US Centers for Disease Control and Prevention (CDC) classified the outbreak as a Level 3 emergency response, which is the agency's lowest level of emergency activation.
CDC officials said passengers will be monitored for about six weeks, which matches the virus's incubation period.
A flight attendant with Dutch airline KLM who had contact with an infected passenger later tested negative for hantavirus, the WHO confirmed Friday.
The infected passenger, the wife of the first person to die, briefly boarded a flight from Johannesburg to the Netherlands on April 25 before being removed before takeoff. She died the next day in a Johannesburg hospital.
Two Singapore residents who had been on the ship tested negative but are still in quarantine, according to authorities there.
British health officials also reported a suspected case on Tristan da Cunha, one of the world's most remote inhabited places, with about 220 people.
Spanish authorities confirmed that a woman who was on the Johannesburg flight is being tested for hantavirus after showing symptoms at home in eastern Spain.
She is in isolation in the hospital, according to Health Secretary Javier Padilla.