Andes hantavirus: epidemiology, outbreaks and guidance

Epidemiology

Andes virus (ANDV) is a type of New World Hantavirus. ANDV infection in humans was first identified in 1995 in Argentina and later the same year in Chile. In 1996 an outbreak of 16 cases occurred in Argentina, and evidence gathered in the investigation suggested person-to-person spread, which is unique in hantavirus infections. ANDV is a cause of hantavirus cardiopulmonary syndrome (HCPS) in South America, which is a potentially fatal, acute medical complication of specific hantavirus infections. There are several ANDV hantavirus strains associated with HCPS.

The virus is naturally carried by wild rodents of the family Cricetidae, especially by the long-tailed pygmy rice rat (Oligoryzomys longicaudatus). People can become infected with ANDV by contact with infected rodents or their excreta (urine and faeces) in South America, principally in Argentina and Chile, and rarely through contact with an infected person. Most cases of ANDV HCPS in Argentina occur across 4 endemic regions: North (Salta, Jujuy), Centro (Buenos Aires, Santa Fe, and Entre Ríos), Northeast (Misiones) and Patagonia (Neuquén, Río Negro, and Chubut). Within Chile, ANDV infections occur mainly in southern Chile and ANDV infection is endemic in the Región de Los Lagos.

Cases are more common in spring and summer, when the number of infected rodents tends to be high and people engage in more outdoor activities, particularly in rural and semi-rural areas. Some years may be associated with an increased risk of exposure, due to favourable climatic conditions and increases in rodent populations. Other hantaviruses found in North and South America can cause HCPS but ANDV is the only hantavirus known to have human-to-human transmission.

See risk map for HCPS caused by ANDV in southern Argentina.

Travel related cases of ANDV infection have occasionally been reported in people returning to the US and Europe from Argentina and Chile, respectively. In May 2026, there was an outbreak of ANDV on a cruise ship which affected a small number of passengers. For current information regarding this outbreak please see the UKHSA update on the hantavirus cruise ship outbreak.

Transmission

Animal-to-human transmission occurs when people come into contact with infected wild rodents, their urine, droppings, saliva or areas contaminated by these rodents, whilst in at-risk areas including Chile and Argentina. It is believed that transmission occurs by inhalation of aerosolized virus particles from rodent excreta (urine and droppings), or dust containing the excreta, or by touching mucous membranes with hands that have been contaminated. Infected rodents do not show signs of disease. Rodent bites are a rare but potential route of transmission.

The route for human-to-human transmission of ANDV has not been confirmed, but it appears that close contact with an infected person is necessary, and airborne transmission of respiratory droplets or viral particles is a possibility. Close contact with infected cases within a household setting has been shown to increase the risk of transmission tenfold, and transmission often occurs in family clusters. Some studies have suggested sexual contact as a potential route of transmission, and others have proposed transmission from contacts with other body fluids such as breast milk and blood. Infectious virus has been detected in human urine samples, suggesting another potential route of transmission.

Epidemiological studies suggest that human-to-human transmission can occur during the prodromal phase, but to date no studies have reported evidence of asymptomatic human-to-human transmission. In late 2018, an outbreak occurred in Chubut province, Argentina. A single suspected symptomatic index case attended a party in Epuyén where secondary transmission is thought to have occurred.

Clinical features

The most important complication of ANDV infection is HCPS, which is associated with a high mortality rate. Milder illness without significant cardio-respiratory compromise may also be seen. Illness usually develops 3 to 4 weeks following exposure, but incubation periods between 9 and 40 days have been described. Clinical features of ANDV infection include an initial prodrome, which may be an influenza-like or non-specific illness, with fever, chills and myalgia (muscle aches), and sometimes gastrointestinal symptoms. Vomiting, diarrhoea and abdominal pain may be the only initial symptoms in some cases. Conjunctivitis and petechiae (a rash of small red/ purple spots that does not fade with pressure) may also be present.

Upper respiratory tract signs and symptoms tend to be absent. In progressive illness, the prodromal symptoms worsen and then acute respiratory compromise and hypotension follow quickly, usually heralded by onset of a dry cough. This represents the cardiopulmonary phase, with capillary leakage in the lungs. Abdominal pain may be present and can be severe.

Complications include respiratory failure, acute respiratory distress syndrome, acute pulmonary oedema, shock, coagulopathy and haemorrhage, and cardiac arrhythmias. Neurological complications are uncommon but encephalopathy, encephalitis, meningitis and seizures may occur. The mortality rate is typically 21% to 50%.

Thrombocytopaenia is common and may be seen in the prodromal phase. Increases in blood lactate dehydrogenase may be seen initially, followed by increases in blood lactate and liver transaminase levels. There may be evidence of acute renal impairment. Neutrophilic leukocytosis and the presence of immunoblasts in peripheral blood may be seen, particularly in more severe disease.

The resolution of the cardiopulmonary phase can also be rapid (over 24 to 48 hours in some cases), but complete recovery from HCPS can be a protracted process.

Patient assessment

ANDV infection is classed as an airborne high consequence infectious disease (HCID) in England and clinical assessment should be performed by specialist hospital staff, with adherence to strict infection prevention and control precautions (see below) to prevent secondary transmission.

The WHO has produced updated case definitions in response to the ANDV outbreak in May 2026. These case definitions are used in context of an ongoing outbreak. Consider ANDV infection in a patient with a relevant travel and exposure history who presents with a compatible illness, particularly severe acute respiratory illness, and the onset of illness was within 8 weeks of a potential exposure.

Visitors to rural areas of Argentina and Chile (for example mountain trekkers and campers) may be at increased risk of ANDV infection, including those who do not report a history of known exposure to rodents and their excreta. ANDV infection is a rare disease and other travel associated and common infections should also be considered in the differential diagnosis.

Any suspected cases in England should be discussed initially with local infection specialists and then with the Imported Fever Service (IFS) (24 hour telephone service: 0844 778 8990). The IFS can advise whether laboratory testing is indicated. The IFS is also available to clinicians in Scotland, Wales and Northern Ireland. Any suspected cases should be notified immediately to the local Health Protection Team.

Laboratory diagnosis

In the UK, the Rare and Imported Pathogens Laboratory (RIPL) at UKHSA Porton Down is the designated diagnostic laboratory. RIPL offers RT-PCR and IgG serological assays for the detection of hantaviruses.

Any suspected case should be discussed initially with local infection specialists and then with the IFS, as above. The IFS can advise on whether laboratory testing is indicated, and if so, will provide advice about the sample types required and transport requirements.

Treatment

There is no proven, specific treatment for ANDV infection, and there is no preventative vaccine. Treatment is supportive. There is no evidence to support the use of ribavirin or corticosteroids in the treatment of HCPS caused by ANDV. Clinical management of confirmed ANDV infection in England must be provided by specialist infectious diseases and critical care teams that are capable of safely managing patients with high consequence infectious diseases.

Patients can deteriorate rapidly and confirmed cases in England should be transferred to an Airborne HCID Treatment Centre quickly, including consideration of whether extracorporeal membrane oxygenation (ECMO) may be required.

Infection prevention and control

Suspected and confirmed ANDV should be managed in line with the airborne HCID guidance.

Appropriate respiratory isolation is essential for suspected and confirmed cases. Enhanced personal protective equipment (PPE) must be used when assessing or providing care to suspected HCID cases in hospitals. Refer to the NHSE HCID guidance here NHS England: Addendum on high consequence infectious disease (HCID) personal protective equipment (PPE) and the UKHSA HCID guidance here High consequence infectious diseases (HCID).

Clinical laboratories should be informed in advance of samples submitted from suspected or confirmed diagnosis of ANDV infection, so that they can perform local risk assessments, minimise risk to laboratory workers and, where appropriate, safely perform laboratory tests that are essential to clinical care. ANDV is an ACDP Hazard Group 3 pathogen.

Advice for travellers to endemic areas

Those travelling to endemic areas in Chile and Argentina, particularly rural areas or areas with known active outbreaks, should avoid contact with rodents or areas that may be infested by rodents (for example where rodent droppings are visible). Basic rural accommodation, such as forest cabins and mountain huts, should be aired before use if the accommodation has been left unoccupied for some time.

Cabins and potential campsites in endemic areas should not be used if rodents, rodent droppings or rodent nests or burrows are identified. If use cannot be avoided, disinfect areas that have signs of rodents. If camping, use a ground sheet and camping mat, and sleep on a camping bed if possible. Observe good hand hygiene by washing hands regularly.

Person-to-person transmission is best prevented by avoiding contact with people with confirmed or suspected HCPS.

For information about current outbreaks and travel advice, visit the National Travel Health Network and Centre (NaTHNaC) website.

UK risk assessment

Although rodent-associated hantavirus infections occur in the UK, there is no risk of ANDV transmission from rodents  in the UK. It is possible that rare, travel-associated infections may be seen in the UK in travellers returning from endemic regions.

The risk of a case from an outbreak area being imported into the UK is very low if appropriate precautions are undertaken whilst travelling to an endemic area.