May 2026

Findings on the Andes (Hanta) Virus Outbreak aboard the Expedition Cruise Ship

The international outbreak of Andes virus from the family Hantaviridae aboard the expedition cruise ship is a significant infectious disease event being closely monitored by the WHO and the ECDC. Andes virus is a New World hantavirus found in South America. In Argentina, 41 confirmed Andes virus cases were recorded in the first four months of this year (1). As of the current status (20 May 2026), eleven cases (two suspected cases) have additionally been reported in association with the cruise ship, with three fatalities (2). In general, humans can become infected through excretions from infected rodents and, following an incubation period of 7 to 49 days, can develop a cardiopulmonary syndrome, which carries a case fatality rate of 20 to 35% (3).

In the meantime, laboratories in South Africa, Senegal, Switzerland, and the Netherlands have succeeded in sequencing the virus (4). The sequences are closely related to the South American Epuyen/18-19 strain, which resembles the Epilink/96 strain (5). As early as 1996 and 2020, it was demonstrated that person-to-person transmission of Andes virus is possible — something not observed with European and Asian hantaviruses. In these cases, the virus is transmitted via bodily fluids such as saliva, nasopharyngeal secretions, semen, and breast milk (3). Since viral titres are highest in the first one to three days after symptom onset, this represents the period of greatest transmission risk.

To date, no evidence of mutations suggesting increased transmissibility or enhanced virulence has been found. The sequence data currently support the hypothesis that the index patient, who died shortly after the ship’s departure from Ushuaia, must have been infected during their expedition stay in Argentina, Chile, or Uruguay through contact with rodent excretions. The subsequent patients were then presumably infected through close contact with this individual on board the expedition vessel.

All contact persons are now being closely monitored and are subject to strict quarantine measures. These can be reviewed on the website of the Robert Koch Institute, which closely aligns with the guidelines of the WHO and the ECDC (6, 7). A distinction is made between asymptomatic and symptomatic contact persons. Asymptomatic contact persons must quarantine for six weeks after the last possible exposure. Home quarantine is generally possible. Should symptoms such as fever, headache, muscle or joint pain, nausea, vomiting, abdominal pain, diarrhoea, cough, or shortness of breath occur, the relevant public health authority must be contacted immediately.

If a contact person becomes symptomatic or tests positive for the virus, they must be monitored in an isolation room. Those caring for these patients must be equipped with personal protective equipment (PPE) consisting of single-use medical gloves, a protective gown, eye protection, and at minimum an FFP2 mask.

It is to be hoped that these strict quarantine measures will prevent further infections and that the chain of transmission can be broken swiftly. The coming weeks will likely yield further valuable insights into the relatively rarely detected Andes virus infections, and will hopefully also contribute to the development of treatment options and vaccines.