THE HAGUE — More than two dozen passengers left a cruise ship hit by a deadly hantavirus outbreak on April 24 without contact tracing, nearly two weeks after the first passenger died on board, the ship operator and Dutch officials said on Thursday.

The news raised concerns that the virus could spread as travelers returned home, though experts say the risk to the wider public is considered low.

The Netherlands-based operator, Oceanwide Expeditions, had previously said the body of the Dutch man who died on April 11 was taken off the ship on the South Atlantic island of St. Helena on April 24, when his wife also disembarked. She then flew to South Africa a day later and died there.

The company said on Thursday that 29 passengers left the vessel at St. Helena, while the Dutch Foreign Ministry put the number at about 40. The company had not previously acknowledged that dozens more left the ship at that time.

The World Health Organization said on Thursday it had informed 12 countries that its nationals had disembarked the ship on St. Helena.

The first confirmed case on the ship was only on May 2, the WHO had previously said. That was in a British man evacuated from the ship to South Africa from Ascension Island three days after the St. Helena stop.

WHO Director-General Tedros Adhanom Ghebreyesus said on Thursday that there were now five confirmed hantavirus cases from the outbreak, with three more suspected, and warned more cases were possible.

The vessel is now sailing to Spain's Canary Islands, a voyage that is expected to take three or four days, with more than 140 passengers and crew members still on board.

Authorities in South Africa and Europe are trying to trace contacts of any passengers who previously got off the ship.

It emerged on Wednesday that a man tested positive for hantavirus in Switzerland after he also disembarked at St. Helena and flew home, though his precise movements are not clear.

Dutch authorities did not confirm where other passengers who disembarked are now.

The WHO said on Thursday it expected the hantavirus outbreak on the ship to be "limited", as long as public health measures and "solidarity" are implemented.

Agencies via Xinhua