The World Health Organization on Thursday declared the hantavirus outbreak aboard the cruise ship MV Hondius over, after the final person under quarantine completed the 42-day monitoring period, tested negative, and returned home. No new cases have been reported since 25 May, WHO Director-General Tedros Adhanom Ghebreyesus told a press briefing in Geneva. The declaration closes a global health alert that began in early May when a cluster of severe respiratory illness was reported on the Dutch-flagged vessel, ultimately resulting in 12 confirmed and one probable case, including three deaths.

The outbreak was caused by the Andes virus, the only known strain of hantavirus capable of sustained human-to-human transmission. Hantaviruses are typically spread by rodents, and no vaccine or specific treatment exists. The ship had departed Ushuaia, Argentina, on 1 April, visiting remote South Atlantic islands before the first fatality occurred at sea on 11 April. A second passenger died in Johannesburg on 26 April, and a third on board on 2 May. The vessel was diverted to Tenerife in Spain’s Canary Islands, where remaining passengers were evacuated on 10 May, and later docked in Rotterdam for deep cleaning and crew quarantine. It was cleared to sail again on 30 May.

Health authorities in 33 countries and territories identified and monitored more than 650 contacts, a cross-border effort that Tedros said demonstrated the value of the International Health Regulations. Spain, the Netherlands, Argentina, South Africa, and the United Kingdom were among the states that coordinated passenger repatriation and medical evacuations. An investigation by Argentina’s health ministry in a second province failed to locate virus-carrying rodents, leaving the exact origin of the outbreak unresolved. The initial hypothesis—that a passenger became infected while travelling in endemic areas of Argentina—remains unconfirmed.

Although the outbreak is over, the WHO is coordinating a study across 21 countries to understand how the disease develops, which it says will support the development of diagnostics, therapeutics, and vaccines. Diana Rojas Alvarez, the WHO’s high-impact epidemics chief, noted that the Andes virus and other hantaviruses continue to pose a public health threat in South America and other endemic regions, requiring sustained surveillance and community preparedness. The WHO also expressed hope that the episode would spur member states to finalise the outstanding section of the Pandemic Agreement later this month, bringing the accord into operation.