What is Andes Virus (ANDV)?
Andes virus (ANDV) is a rare but highly lethal hantavirus native to South America. Unlike most hantaviruses, it is unique in its capacity for person-to-person transmission — a characteristic that makes it one of the most closely monitored emerging infectious diseases in the world.
Background & Discovery
Andes virus was first identified in 1995 in southern Argentina and Chile following an outbreak of severe respiratory illness that killed several people. Scientists quickly recognized it as a new member of the Hantaviridae family and named it after the Andes mountain range where early cases were concentrated.
Hantaviruses are a globally distributed group of rodent-borne viruses. Most cause either hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia, or hantavirus pulmonary syndrome (HPS) in the Americas. ANDV is the primary cause of HPS in South America and is responsible for the majority of hantavirus deaths on that continent.
- Family: Hantaviridae
- Genus: Orthohantavirus
- Species: Andes orthohantavirus
- Genome: Tripartite, negative-sense single-stranded RNA
- Natural Reservoir: Oligoryzomys longicaudatus (long-tailed pygmy rice rat)
How Is Andes Virus Transmitted?
The primary route of ANDV transmission to humans is inhalation of aerosolized particles from the urine, feces, or saliva of infected long-tailed pygmy rice rats. Activities that disturb rodent habitats — such as clearing brush, entering rarely used cabins, or working in agricultural fields — significantly raise exposure risk.
Person-to-Person Transmission: A Unique Risk
What distinguishes ANDV from virtually every other hantavirus on Earth is its documented capacity for human-to-human transmission. Multiple outbreak investigations in Argentina and Chile have confirmed that close, sustained contact with an infected person — particularly household members and healthcare workers providing intimate care — can result in secondary cases.
"Andes virus remains the only hantavirus for which direct human-to-human spread has been epidemiologically confirmed."
The exact mechanism of person-to-person spread is not fully understood, but respiratory secretions are the leading hypothesis. Standard droplet precautions, contact precautions, and appropriate PPE use are recommended when caring for suspected or confirmed ANDV patients.
- Cleaning or entering enclosed spaces with rodent infestations
- Agricultural work in rural Andean regions
- Hiking or camping in temperate forests of Argentina and Chile
- Handling wild rodents without gloves or respiratory protection
- Close, prolonged contact with confirmed ANDV patients without PPE
Geographic Distribution
ANDV circulates primarily along the temperate southern cone of South America, matching the range of its reservoir host. Active transmission zones include:
| Country | Primary Regions Affected | Notes |
|---|---|---|
| Argentina | Patagonia, Neuquén, Río Negro, Chubut | Highest reported case burden |
| Chile | Araucanía, Los Lagos, Aysén | Significant outbreak history |
| Uruguay | Northern and central regions | Sporadic cases reported |
| Bolivia | Andean valleys | Limited surveillance data |
| Brazil | Southern states | Genetically related strains |
Symptoms & Clinical Progression
Hantavirus pulmonary syndrome caused by ANDV follows a predictable but rapidly escalating clinical course. The incubation period is typically 2 to 4 weeks after exposure, though it can range from days to over a month.
Phase 1: Febrile Prodrome (Days 1–5)
Initial symptoms are non-specific and easily mistaken for influenza or other viral illnesses:
- High fever (typically above 38.5°C / 101.3°F)
- Severe myalgia (muscle aches), especially in the lower back and thighs
- Headache and fatigue
- Nausea, vomiting, and abdominal pain
- No cough or respiratory symptoms at this stage
Phase 2: Cardiopulmonary Phase (Days 5–10)
This is the life-threatening stage. Rapid deterioration can occur within hours:
- Sudden onset of cough and shortness of breath
- Pulmonary edema (fluid accumulation in the lungs)
- Cardiogenic shock and hypotension
- Decreased oxygen saturation requiring mechanical ventilation
ANDV's cardiopulmonary phase can progress from mild respiratory symptoms to full respiratory failure within 24–48 hours. Any traveler returning from an endemic region who develops fever plus myalgia should seek immediate medical attention and disclose travel history to a physician.
Phase 3: Convalescence
Survivors typically begin recovering after 7–10 days of intensive care. Full recovery of lung function may take weeks to months, and some patients report lasting fatigue.
Diagnosis
Early diagnosis is critical but challenging because the prodromal phase is clinically indistinguishable from many other febrile illnesses. Physicians must maintain a high index of suspicion in anyone with relevant exposure history in endemic areas.
- RT-PCR: Detects viral RNA in blood during the febrile phase — most sensitive early tool
- IgM/IgG ELISA serology: Detects antibody responses; IgM typically appears at symptom onset
- Immunohistochemistry (IHC): Used on post-mortem tissue samples
- Western blot: Confirmatory testing
- Chest X-ray / CT: Shows bilateral interstitial infiltrates as disease advances
- CBC: Thrombocytopenia, elevated hematocrit, and atypical lymphocytes are hallmarks
In many endemic areas, specialized testing must be sent to reference laboratories such as PAHO-affiliated centers or the CDC's Special Pathogens Branch, which can cause diagnostic delays. Clinical diagnosis guided by epidemiological context remains essential.
Treatment & Management
There is currently no FDA-approved antiviral treatment for ANDV or any other hantavirus. Management is entirely supportive and must be intensive.
Supportive Care Priorities
- Careful fluid management (avoid aggressive hydration — worsens pulmonary edema)
- Supplemental oxygen and early mechanical ventilation if saturations fall
- Extracorporeal membrane oxygenation (ECMO) in severe cardiopulmonary failure
- Vasopressors and inotropes for hemodynamic support
- ICU-level monitoring with frequent reassessment
Investigational Therapies
Ribavirin, a broad-spectrum antiviral, showed promise in early laboratory studies against ANDV but has not demonstrated consistent clinical benefit in human trials. Research into monoclonal antibodies (particularly human convalescent plasma-derived antibodies) has shown encouraging results in animal models. As of 2025, multiple vaccine candidates are in early-phase development.
Prevention & Risk Reduction
Because there is no approved vaccine and no reliable cure, prevention is paramount. The following measures are recommended by the WHO, CDC, and regional health authorities:
Rodent Control
- Seal gaps, cracks, and holes in buildings to block rodent entry
- Store food (including pet food) in sealed, rodent-proof containers
- Use snap traps rather than glue traps (minimize aerosol from struggling rodents)
- Reduce brush, woodpile, and debris near living areas that attract rodents
Safe Cleaning Procedures
- Never vacuum or sweep rodent droppings — this aerosolizes particles
- Wear rubber gloves and an N95 or better respirator before cleaning
- Wet droppings with a 1:10 bleach solution before wiping and bagging
- Wash hands thoroughly after handling any potentially contaminated materials
Outdoor & Travel Precautions
- Sleep on elevated surfaces — avoid ground-level bedding in rodent-prone areas
- Use a tent with a sewn-in groundsheet
- Air out uninhabited cabins thoroughly before entering
- Inform your physician of travel to endemic regions if you develop fever and myalgia upon return
Public Health Significance
ANDV is classified as a Category A Bioterrorism Agent by the CDC and is subject to biosafety level 4 (BSL-4) laboratory protocols due to its high lethality and lack of countermeasures. Outbreaks are closely monitored by the Pan American Health Organization (PAHO) and national health ministries in Argentina and Chile, both of which operate active surveillance programs.
While total case numbers remain relatively low — with dozens to low hundreds of confirmed cases annually across the continent — the case fatality rate of approximately 35–40% makes ANDV one of the deadliest viral infections currently circulating in the Western Hemisphere.
Climate change is an emerging concern. Shifts in precipitation, temperature, and land use are altering rodent population dynamics and potentially expanding the geographic range of O. longicaudatus, which could bring ANDV into areas where it has not historically occurred.
Research & Future Directions
ANDV's person-to-person transmissibility and high lethality have made it a priority pathogen for research funding agencies including the U.S. National Institutes of Health (NIH) and the Coalition for Epidemic Preparedness Innovations (CEPI).
Key areas of active investigation include:
- Vaccine development: DNA vaccines and mRNA platforms have shown efficacy in Syrian hamster models — the gold standard for ANDV research
- Monoclonal antibodies: Neutralizing antibodies derived from survivors have demonstrated post-exposure protection in animal studies
- Antiviral drug screening: High-throughput screens at BSL-4 facilities are evaluating repurposed drugs
- Understanding human-to-human transmission: Outbreak genomic sequencing is helping map transmission chains and routes
Summary
Andes virus is a severe and frequently fatal respiratory pathogen unique among hantaviruses for its ability to spread from person to person. Caused by close contact with infected long-tailed pygmy rice rats or their contaminated secretions — and occasionally by contact with ill patients — ANDV causes a rapid, devastating pulmonary syndrome with no approved cure.
For travelers to southern South America, outdoor workers, and rural residents in endemic regions, awareness of exposure risks and early medical consultation at the first sign of febrile illness after potential exposure are the most powerful tools currently available.
Continued international investment in vaccines and antivirals will be essential to reducing the toll of this dangerous emerging virus in the decades ahead.
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