The World Health Organization has called for 42 days of active health monitoring for everyone who was aboard the MV Hondius, an expedition cruise ship, after an Andes hantavirus outbreak on board killed three people and infected several others.

Andes hantavirus is a rare and serious respiratory illness spread primarily through contact with infected rodents or their droppings. Unlike most hantavirus strains, the Andes variant is the only one known to spread person-to-person, which is why WHO's response focuses on tracing and watching all contacts aboard the vessel, not just those who showed symptoms.

Why 42 Days of Monitoring

The 42-day window reflects twice the maximum known incubation period for hantavirus, a standard public health buffer to catch late-developing cases. Anyone who shared close quarters on the ship could have been exposed, making the full passenger and crew list the relevant cohort. Expedition vessels like the MV Hondius typically carry a mix of international travelers, which complicates contact tracing across multiple countries.

Hantavirus carries a high fatality rate once it progresses to severe pulmonary disease. There is no approved antiviral treatment, so early detection and supportive hospital care are the main tools available. Rapid identification of new cases among those monitored would allow faster medical intervention and limit further spread.

What This Means Going Forward

Health authorities in the home countries of passengers and crew will likely need to coordinate the monitoring, since travelers will have dispersed after disembarking. WHO's call for active surveillance, rather than passive self-reporting, means regular check-ins and symptom screening, not just an advisory to seek care if unwell.

The outbreak is unusual given that documented person-to-person Andes hantavirus clusters are rare, and a ship setting with recirculated air and close living conditions adds complexity. Public health agencies will be watching whether any secondary cases emerge among those monitored, which would help establish the transmission chain and the outbreak's full scale.