Skip to content 
However, the Andes virus — the strain implicated in the cruise ship outbreak — is different. It is one of the only hantaviruses known to occasionally spread between people through close contact. Experts believe transmission likely occurs through respiratory secretions during prolonged exposure, especially among family members or caregivers.
This rare ability to spread between humans significantly elevated concern among global health authorities once the outbreak was identified.Family
Investigators Focus on “Patient Zero”
One of the biggest questions surrounding the outbreak has been simple but critical: who brought the virus onto the ship?
Investigators now believe they may have identified the likely “patient zero” — the first infected individual linked to the outbreak. Reports indicate that a Dutch ornithologist named Leo Schilperoord may have unknowingly contracted the virus before boarding the vessel during travels in Argentina. Authorities suspect he may have been exposed while visiting a landfill area during a birdwatching excursion.
Landfills can attract rodents, which are the primary carriers of hantavirus. Investigators believe contaminated rodent droppings or urine in the area may have exposed the traveler to the virus. According to reports, he later boarded the cruise ship while incubating the infection, before symptoms became severe.
Once onboard, close interactions among passengers may have allowed the virus to spread further. Cruise ships naturally create environments where travelers spend long periods in enclosed shared spaces, dine together, and participate in group excursions. Those conditions can facilitate transmission when an infectious disease is present.
Although officials continue investigating, the landfill exposure theory currently appears to be the strongest explanation for the origin of the outbreak.
Why the Andes Virus Is Different
Most hantavirus strains are not considered highly contagious between humans. That is why outbreaks involving person-to-person spread are exceptionally unusual. The Andes virus, however, has long worried infectious disease experts because it breaks that rule.
The Andes strain is primarily found in Argentina and Chile. Several previous outbreaks in South America demonstrated that infected individuals could transmit the virus to close contacts under certain conditions. However, experts emphasize that transmission still appears relatively inefficient compared with viruses such as influenza or COVID-19.
Health authorities say prolonged close exposure is usually required for spread to occur. Casual interactions are believed to pose much lower risk. Nonetheless, the cruise ship environment raised concern because passengers often share cabins, dining areas, and activity spaces for extended periods.
Scientists are also studying whether the virus involved in this outbreak may have undergone genetic changes. French officials stated that sequencing data so far shows no evidence of significant mutation, though investigations remain ongoing.