# Andes virus

> Hantavirus strain present in South America (Argentina, Chile). The only hantavirus with documented human-to-human transmission. Leading cause of severe pulmonary syndrome.

Canonical source: https://hantatracker.fr/en/glossary/andes-virus/

**Aliases**: ANDV, Andes hantavirus, Andes virus, orthohantavirus andes

**Andes virus** (*Orthohantavirus andesense*, code ANDV) is a New World hantavirus present in South America, mainly in Argentina and Chile. It is responsible for the most severe form of hantavirus pulmonary syndrome in humans and has the distinctive feature, unique among hantaviruses, of being capable of documented human-to-human transmission. This characteristic makes it one of the hantaviruses most closely monitored by international health authorities.

## Virology

### Classification

Andes virus belongs to the genus *Orthohantavirus*, family Hantaviridae, order Bunyavirales. Its official name according to the International Committee on Taxonomy of Viruses (ICTV) is *Orthohantavirus andesense*. It was first identified in Argentina in 1995 during pulmonary syndrome episodes in the Andean region. The virus shares its genomic architecture with other hantaviruses: three segments of negative-sense RNA (S, M, L) encoding the nucleocapsid protein, the envelope glycoproteins and the polymerase.

### Genotypes

Several lineages circulate in South America, including the Sout lineage (Argentina, Chile) and variants linked to specific outbreaks. The Epuyén/18-19 strain, isolated during the 2018-2019 Argentine outbreak, carries mutations associated with increased human-to-human transmission that have been characterised in molecular virology and published by Argentina's CONICET.

## Animal reservoir

### Long-tailed rat

The main reservoir of Andes virus is the rodent *Oligoryzomys longicaudatus*, also called the colilargo. This sigmodontine rodent is endemic to the southern Andes range, from southern Peru down to Tierra del Fuego. It colonises diverse habitats: temperate forests, Patagonian steppes, agricultural edges. Its population density varies sharply with the cyclical proliferation of *Chusquea* bamboo, whose seeds are a major food resource.

### Viral shedding

As with other hantaviruses, infection in the rodent is chronic and asymptomatic. The virus is shed throughout the animal's life in urine, faeces and saliva. Viral density in excretions is highest in young infected rodents.

## Transmission

### Usual route (animal to human)

The main route is inhalation of aerosols from rodent excretions. Direct contact (skin lesion, mucous membranes) or bites are possible but minor routes. At-risk activities include cleaning rural areas frequented by rodents, forestry work, and adventure travel in endemic areas.

### Human-to-human transmission

Andes virus is **the only hantavirus** for which human-to-human transmission has been demonstrated by epidemiological studies. Transmission accounts for between 2 and 5 percent of all cases. It requires close, prolonged contact with a symptomatic person: shared household, direct care without protective equipment, or exposure to superspreader events.

The **Epuyén** outbreak (Argentina, 2018-2019), studied in the NEJM, has become the benchmark: 18 confirmed cases, 11 deaths, spread triggered by 3 symptomatic patients at social events. The observed reproduction number R fell from 2.12 before quarantine measures to 0.96 after they were put in place — showing both the transmission potential and the effectiveness of isolation.

## Relevance for the MV Hondius

The identification of Andes virus by PCR on 3 May 2026 in MV Hondius patients triggered an international surveillance operation. Authorities believe the first patients were contaminated **before boarding**, during stays in South America. The continuation on board of human-to-human transmission, suspected by the WHO on 7 May 2026, justifies the follow-up of passengers and contacts for 42 days after their last exposure.

The WHO assesses the risk to the general population as **low**: transmission requires close contact, the virus is not adapted to broad airborne spread, and MV Hondius passengers are under individual medical follow-up in 23 countries.