Andes virus

ANDV · HPS

Overview

Andes virus is the dominant hantavirus strain in southern South America and is unique among hantaviruses for documented person-to-person transmission. The principal reservoir is the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), which inhabits forested and rural areas of Patagonia and the Andean foothills. Andes virus produces hantavirus pulmonary syndrome (HPS) clinically similar to Sin Nombre virus disease in North America. Person-to-person transmission has been most clearly documented during the 2018–2019 Epuyén outbreak in Argentina.

Discovery

Andes virus was isolated in 1995 by Argentine and Chilean investigators following a cluster of HPS cases in El Bolsón, Río Negro Province, Patagonia. Sequencing distinguished the new strain from Sin Nombre virus and other South American hantaviruses, and field trapping identified Oligoryzomys longicaudatus as the principal reservoir. The 1995–1996 outbreak in southern Argentina included a striking observation: secondary cases occurred in close contacts of index patients in patterns inconsistent with rodent-only exposure, giving the first epidemiologic evidence of person-to-person hantavirus transmission.

Rodent reservoir

The long-tailed pygmy rice rat (Oligoryzomys longicaudatus) is a small sigmodontine rodent native to the temperate forests, ecotones, and rural agricultural zones of southern Argentina and Chile. It favours habitat edges, woodpiles, sheds, and the immediate periphery of rural dwellings. Population irruptions tied to mass-flowering events of native bamboo (Chusquea spp.) — a phenomenon known locally as ratada — have historically preceded outbreaks of human Andes virus disease, most notably the 1997 ratada in Aysén, Chile.

Transmission

Most Andes virus infections occur through inhalation of aerosolized rodent excreta in rural or peri-rural settings — cabins, outbuildings, sheds, agricultural workplaces — similar to other New World hantaviruses. What distinguishes Andes virus is documented person-to-person transmission via respiratory droplets and close prolonged contact, most clearly during the 2018–2019 Epuyén outbreak in which a single index case seeded a multi-month, multi-generation chain of infection. Casual contact has not produced documented transmission; close household, intimate, or unprotected medical contact appears necessary.

Clinical course

Andes virus produces a clinical course closely resembling Sin Nombre HPS: an incubation period of approximately one to five weeks, followed by a prodromal phase of fever, myalgia, and gastrointestinal symptoms, and then a cardiopulmonary phase characterized by non-cardiogenic pulmonary edema, hypotension, and shock. Hemorrhagic manifestations are uncommon but reported. The Andes virus disease appears slightly more likely to involve significant gastrointestinal symptoms in the prodrome than Sin Nombre HPS.

Diagnosis

Diagnosis is by serology (IgM and IgG against Andes virus antigens) and RT-PCR on blood, plasma, or respiratory secretions at reference labs in Argentina (Instituto Malbrán) and Chile. Routine bloodwork findings mirror those of Sin Nombre HPS — thrombocytopenia, immunoblast proliferation, hemoconcentration, elevated LDH. In outbreak settings with documented person-to-person spread, contact tracing and serologic follow-up of close contacts is part of the diagnostic and public-health response.

Treatment & prognosis

Treatment is supportive: early ICU admission, careful fluid management, mechanical ventilation, vasopressors, and ECMO for severe cardiopulmonary collapse. Small Argentine studies have suggested possible benefit from convalescent immune plasma collected from recovered patients, but evidence remains limited and the intervention is not standard of care. Case-fatality is approximately 30–40% overall and varies with healthcare access; rural patients with delayed presentation fare worse than urban patients.

Prevention

Standard New World HPS prevention applies — rodent exclusion, no dry sweeping or vacuuming, N95 respirator and bleach disinfection before cleaning rodent-affected enclosed spaces. Because Andes virus is the only hantavirus with documented person-to-person spread, healthcare workers caring for confirmed cases should use airborne and droplet precautions, and close household contacts should be advised about possible transmission risk. Argentine and Chilean health ministries have issued targeted seasonal warnings during ratada years.

Tracked countries

Live risk index and news for countries where Andes virus is documented or surveilled.

Notable outbreaks

1. 1995
   El Bolsón, Río Negro, Argentina

   First identification of Andes virus and the first documentation of person-to-person hantavirus spread.

2. 1996
   Aysén Region, Chile

   Family cluster suggesting close-contact transmission between household members.

3. 1997
   Aysén Region, Chile (ratada)

   Large outbreak following mass flowering of native bamboo and explosive Oligoryzomys population growth.

4. 2018–2019
   Epuyén, Chubut, Argentina

   Roughly 34 confirmed cases and 11 deaths over several months — one of the largest documented person-to-person hantavirus outbreaks.

References & primary sources

• PAHO — Hantavirus
• Argentina — Boletín Epidemiológico Nacional
• MINSAL Chile — Departamento de Epidemiología
• Instituto Malbrán (Argentina) — Hantavirus

Other hantavirus strains