Andes virus and Sin Nombre virus are the two most important hantaviruses for HPS in the Americas, with distinct geography and transmission profiles.
Andes virus and Sin Nombre virus are the two most important hantaviruses for HPS in the Americas, with distinct geography and transmission profiles.
Sin Nombre virus is the US species, reservoired by deer mice (Peromyscus maniculatus); it is not known to transmit between humans. Andes virus is the South American species, reservoired by the long-tailed pygmy rice rat; it is the only hantavirus with documented human-to-human transmission and is the strain in the current MV Hondius cluster.
Hantaviruses are reservoired in specific rodent species and acquired by humans primarily through aerosolised dust in rodent-infested spaces. The Andes virus strain — the one in the 2026 MV Hondius cluster — is the single known exception with documented human-to-human transmission, and even that requires close, sustained contact.
Influenza, COVID-19, and other respiratory viruses transmit far more efficiently between humans via respiratory aerosols, which is why outbreak dynamics differ so dramatically.
Hantavirus pulmonary syndrome (HPS) has a case fatality rate of 36–50% in the Americas. Influenza fatality is well below 0.1%. COVID-19 fatality has varied by variant and population but has generally been around 1% for known cases.
Hantavirus is significantly more lethal than either, but its low transmissibility and low case count keep its public-health impact much smaller in absolute terms.
There is no specific antiviral treatment for hantavirus. Care is supportive — oxygen, fluid management, mechanical ventilation, and ECMO in severe cases. Survival depends heavily on early hospital recognition.
Influenza has effective antivirals (oseltamivir, baloxavir) and vaccines. COVID-19 has effective antivirals (Paxlovid) and vaccines. Hantavirus has neither in Western countries.
→ See the live MV Hondius tracker, full timeline, and 15 hantavirus news sourcesOn a per-case basis, hantavirus pulmonary syndrome is far more dangerous than flu or COVID-19, with a 36% case fatality rate. On a population-health basis, however, COVID-19 and flu cause vastly more total illness and death because they transmit between humans efficiently and hantavirus does not.
Because the suspected Andes virus strain is the only hantavirus with documented human-to-human transmission, and a contained shipboard cluster is a natural experiment for studying onward spread under close-contact conditions.
WHO and independent virologists assess pandemic potential as very low. Andes virus has been studied for three decades without a single uncontrolled outbreak in that time, and the natural rodent reservoir is geographically limited.