Hantavirus — Andes Strain

Andes orthohantavirus (ANDV) is a single-stranded RNA virus in the family Hantaviridae, first characterised after a 1995–1996 outbreak in El Bolsón, Argentina. Its natural reservoir is the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), known locally as the colilargo, which sheds the virus in urine, faeces, and saliva. Humans typically inhale aerosolised particles from rodent excreta in confined spaces — barns, sheds, woodpiles, and vacation cabins reopened after winter storage.

What sets Andes apart is that, unlike every other known hantavirus, it can also spread person-to-person. The epidemiological signal first emerged from clusters around El Bolsón in 1996 and was confirmed at the molecular level twenty years later through whole-genome sequencing during the 2018–2019 Epuyén outbreak in Chubut Province, Argentina (Martinez et al., NEJM 2020).

Hantaviruses split broadly into two clinical and geographic groups. Old World hantaviruses (Hantaan, Seoul, Puumala, Dobrava) cause haemorrhagic fever with renal syndrome (HFRS). New World hantaviruses (Sin Nombre, Andes, Laguna Negra) cause hantavirus pulmonary syndrome (HPS). Andes virus is the only entry in the family with confirmed person-to-person spread.

Source: ICTV taxonomy and CDC Hantavirus; transmission classifications follow the World Health Organization and PAHO position that only Andes virus has produced verified person-to-person chains.

There are two pathways:

1. Rodent-to-human (primary). Aerosolised particles from infected rodent urine, faeces, or saliva enter the human respiratory tract. Risk increases sharply in poorly ventilated enclosed spaces — rural sheds, agricultural buildings, and cabins reopened after seasonal storage. Direct rodent bites are documented but rare. See CDC: Hantavirus Transmission.
2. Person-to-person (Andes-unique). Close, sustained contact in household or healthcare settings has produced verified transmission chains. Sequencing acute-phase samples from the 2018–2019 Epuyén outbreak, Martinez and colleagues (Valeria P. Martinez et al., New England Journal of Medicine, December 2020) reconstructed multiple super-spreader-driven transmission chains and established direct person-to-person Andes virus spread at the genomic level. Transmission appears most likely during the prodromal phase, when patients have non-specific flu-like symptoms but high viraemia.

The clinical course unfolds in three phases:

Patients who reach the cardiopulmonary phase require intensive care, frequently mechanical ventilation, and in severe cases extracorporeal membrane oxygenation (ECMO). Where ECMO is initiated early, survival rates improve substantially — though access remains uneven outside major referral centres.

The case fatality rate (CFR) reported by the U.S. Centers for Disease Control and Prevention for Andes virus and the related New World hantaviruses is approximately 35% (CDC Hantavirus). Argentinian and Chilean surveillance over the 1995–2019 period puts the figure between 25 and 40 percent depending on year and province (PAHO Hantavirus).

For comparison: Sin Nombre virus reports a CFR around 36% in U.S. surveillance, Seoul virus around 1–2%, and Puumala virus under 1%. Andes virus sits at the high end of hantavirus lethality.

There is no specific antiviral therapy approved for Andes virus. Treatment is entirely supportive:

• Oxygen and mechanical ventilation for respiratory failure
• Vasopressors and fluid management for cardiogenic shock
• ECMO in centres equipped for it — strong evidence of mortality benefit when initiated early in the cardiopulmonary phase

Ribavirin, which shows some activity against Old World hantaviruses causing HFRS, has not demonstrated benefit against hantavirus pulmonary syndrome in controlled studies and is not part of standard Andes virus management (Mertz et al., Clinical Infectious Diseases, 2004).

No vaccine for Andes virus has been licensed in any country as of 2026 (CDC Hantavirus). The only approved hantavirus vaccines worldwide are inactivated formulations directed at Hantaan and Seoul virus, licensed only in China and South Korea — they offer no cross-protection against Andes virus. DNA vaccine candidates targeting hantavirus pulmonary syndrome have remained in preclinical and early-phase development at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), with none yet advanced to widespread availability.

The 2026 MV Hondius cluster is the most geographically distributed Andes virus outbreak on record. Originating on a Dutch cruise ship that departed Ushuaia, Argentina on 1 April 2026, confirmed cases have since been reported across Argentina, Chile, the Netherlands, and additional countries via repatriation. The shipboard setting — shared confined ventilation, sustained close contact among passengers — is consistent with conditions under which Andes virus person-to-person transmission has previously been documented.

For current per-country case counts and primary source links, see the live outbreak map.