Andes virus

Discovery and history

Andes virus was isolated in 1995 from cases in El Bolsón, in the Argentine province of Río Negro, and was named for the mountain range running through its endemic region. The following year, an outbreak in the same town produced evidence that fundamentally changed hantavirus epidemiology: case clusters in family members and physicians who had attended the index patients in Buenos Aires showed transmission patterns that could not be explained by shared rodent exposure. Genetic sequencing of the patient isolates confirmed direct human-to-human spread — the first such evidence for any hantavirus. Subsequent outbreaks have repeatedly reproduced the finding.

Rodent reservoir

The primary reservoir is the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), a small nocturnal rodent native to the Patagonian forests and steppes of Argentina and Chile. Like other hantavirus reservoirs, infected animals are persistently and asymptomatically infected and shed virus throughout life. The rodent prefers brushy forest edges and the bunchgrass habitats of southern South America, putting it in contact with rural and peri-urban human settlements where its populations periodically expand following bamboo (caña colihue) seeding events that release abundant food.

Geographic distribution

Andes virus circulates in Argentina, Chile, Bolivia, Paraguay, and Uruguay. The highest case densities are in southern Argentina (Río Negro, Chubut, Neuquén, Tierra del Fuego) and southern Chile (Aysén, Los Lagos, Los Ríos). Both countries operate national notifiable-disease surveillance. Other Andes-virus-family lineages have been described in Brazil (Araraquara virus, Juquitiba virus) and elsewhere across the region — clinically similar but genetically distinct.

Clinical features

The clinical course mirrors Sin Nombre virus infection: a one-to-eight-week incubation, then a febrile prodrome with severe myalgia, then a cardiopulmonary phase with pulmonary edema and shock. Case-fatality is similar at 35 to 40 percent. The crucial epidemiological difference is the documented person-to-person transmission — close family contacts, healthcare workers, and acquaintances can be infected through respiratory droplets and possibly fomites during the symptomatic phase of an index case. Documented incubation periods for human-acquired cases extend to about 45 days, the period over which exposed contacts are monitored.

Notable outbreaks

The 1996 El Bolsón outbreak (Argentina) provided the original evidence of person-to-person transmission. The 2018 to 2019 Epuyén outbreak in Chubut province produced 29 cases and 11 deaths across at least three generations of transmission and prompted provincial-level quarantine measures unprecedented for a hantavirus event. The 2025 to 2026 multi-country cluster among passengers and crew of an expedition cruise — currently tracked on this site — appears to involve Andes virus contracted in Tierra del Fuego.

Prevention

In addition to standard rodent-exposure precautions, Andes virus is the one hantavirus where person-to-person transmission protocols matter. Public health response in Argentina and Chile includes respiratory isolation of symptomatic cases, contact tracing for close contacts during the symptomatic period, and 45-day monitoring of contacts for incubation-period symptoms. Travelers to endemic regions during periods of known outbreak should follow local public health guidance.

Where Andes virus circulates

Documented in the following countries. Click through for country-specific context, active outbreak status, and historical cases.

Related strains

• SNV The dominant North American hantavirus, causing hantavirus pulmonary syndrome (HPS) with a ~36% case-fatality rate. Discovered during the 1993 Four Corners outbreak.

Synthesized from the World Health Organization Hantavirus Fact Sheet, the U.S. Centers for Disease Control and Prevention Hantavirus Disease pages, the European Centre for Disease Prevention and Control surveillance atlas, and primary epidemiological literature. Not a substitute for individual medical advice. If you have been exposed to rodents and develop symptoms, contact a healthcare professional.

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