Andes virus is the strain at the centre of the 2026 MV Hondius cruise ship outbreak — and it is unique among all known hantaviruses. According to the US Centers for Disease Control and Prevention (CDC), it is the only hantavirus known to spread from person to person. Everything else about hantavirus — its rodent reservoir, its route of transmission, its lack of vaccine or specific treatment — applies to Andes virus as well, but that single extra capability makes it the most closely watched hantavirus strain in the world.
Here is what the CDC says about Andes virus, expanded with 2026 outbreak context.
What Is Hantavirus Andes?
Andes virus (ANDV) is a type of hantavirus — a family of RNA viruses carried by rodents — that causes Hantavirus Pulmonary Syndrome (HPS), a severe and potentially fatal respiratory disease in humans. It circulates primarily in South America, where its main reservoir is the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), found across Argentina and Chile.
Unlike other hantaviruses, the rodents that carry Andes virus have not been found in the United States. US residents are therefore not at risk from environmental exposure — but, as the 2026 Hondius cluster demonstrates, they can be infected through close contact with a patient who acquired the virus in South America or on a vessel that had rodent contamination in southern waters.
How Hantavirus Andes Spreads: Three Routes
The CDC identifies three routes of Andes virus transmission:
1. Contact with infected rodents or their excreta
The primary transmission route — as with all hantaviruses — is inhalation of aerosolised rodent urine, faeces, or saliva. The long-tailed pygmy rice rat sheds Andes virus continuously. Enclosed, poorly ventilated spaces where rodent activity has occurred are the highest-risk environments.
2. Contact with contaminated surfaces
The virus can survive on environmental surfaces for several hours under cool, moist conditions. Touching a contaminated surface and then touching your mouth, nose, or eyes can transfer the virus.
3. Close contact with a sick person — the unique Andes characteristic
This is what distinguishes Andes virus from every other hantavirus. The CDC states explicitly:
“Andes virus is the only type of hantavirus that is known to spread person-to-person. This spread is usually limited to people who have close contact with a sick person. This includes direct physical contact, prolonged time spent in close or enclosed spaces, and exposure to the sick person’s body fluids.”
Importantly, the CDC also notes that people are typically only infectious while they have symptoms — not during the incubation period. This limits the window of transmission risk but does not eliminate it, since symptoms can be present for days before a patient is diagnosed.
Signs and Symptoms of Hantavirus Andes
Incubation period: 4 to 42 days
The CDC specifies an incubation range of 4 to 42 days after exposure — substantially wider than many other viral infections. A Lancet correspondence published in May 2026 documented a Hondius cluster case with a 38-day incubation, confirming that the upper end of this range is real and clinically relevant. This is why the CDC extended monitoring recommendations for Hondius contacts to 45 days.
Early symptoms (prodromal phase)
The CDC lists three cardinal early symptoms:
- Fatigue
- Fever
- Muscle aches, especially in large muscle groups — thighs, hips, back, and sometimes shoulders
These are present in virtually all HPS cases. They are indistinguishable from severe influenza without additional context (exposure history, laboratory findings).
Additional symptoms — present in approximately half of patients
- Headaches
- Dizziness
- Chills
- Gastrointestinal symptoms: nausea, vomiting, diarrhoea, abdominal pain
The GI symptoms are more prominent with Andes virus than with Sin Nombre virus (the dominant US strain), which can help differentiate the two in clinical settings.
What happens next
If unrecognised and untreated, the disease progresses to the cardiopulmonary phase: shortness of breath, low blood pressure, fluid filling the lungs. The CDC emphasises that symptoms can develop rapidly — the transition from prodrome to respiratory crisis can occur within hours. This rapid progression is why early medical care is characterised as critical.
Treatment: No Vaccine, No Specific Antiviral
The CDC is direct: there is no specific antiviral treatment or vaccine for Andes virus currently available.
Ribavirin — an antiviral that showed some early promise — has not demonstrated survival benefit in clinical trials for established HPS. Research into ribavirin for very early Andes virus infection (before the cardiopulmonary phase) continues, but no treatment is approved.
Management is entirely supportive:
- Mechanical ventilation to maintain oxygenation
- Vasopressors to maintain blood pressure
- ECMO (extracorporeal membrane oxygenation) at specialist centres for refractory cases
- Careful fluid management to avoid worsening pulmonary oedema
The absence of targeted treatment makes early recognition the single most important variable in survival. Patients who reach ICU care before respiratory failure begins have substantially better outcomes.
Reducing Your Risk: CDC Guidance
For travellers to South America
- Avoid areas infested with rodents — particularly enclosed spaces such as rural cabins, barns, storage areas
- Do not camp or sleep directly on the ground in endemic areas
- If cleaning a rodent-infested space, wet down surfaces with bleach solution first, wear gloves and a properly fitted respirator, ventilate thoroughly before entering
- Seek immediate medical care if you develop fever and muscle aches within 6 weeks of returning from South America
For people in contact with a confirmed Andes virus patient
The CDC’s person-to-person prevention guidance is specific:
| Risk behaviour | Recommendation |
|---|---|
| Kissing / sexual contact | Avoid with a potentially infected person |
| Sharing drinks, cigarettes, vapes | Avoid |
| Sharing eating utensils or food | Avoid |
| Physical proximity in enclosed spaces | Maintain distance |
| Hand hygiene | Wash hands frequently |
Healthcare workers should use standard contact and droplet precautions. Full airborne precautions (N95 respirator, negative pressure room) are recommended during aerosol-generating procedures such as intubation or bronchoscopy.
Hantavirus Andes in 2026: The Hondius Context
The CDC’s Andes virus page was updated on 9 May 2026 — reflecting the agency’s heightened focus on the MV Hondius outbreak. The agency has also published a dedicated FAQ page on the cruise ship cluster and extended its recommended monitoring window for Hondius contacts from 21 to 45 days, specifically to capture cases at the long end of the 4–42 day incubation range.
As of 12 May 2026, the Hondius cluster stands at 10 confirmed cases across 8 countries and 3 deaths. WHO genomic sequencing released the same day confirmed all cases carry highly similar Andes virus sequences, consistent with a single source event — but cannot yet distinguish between a shared environmental exposure (contaminated rodent excreta on the vessel) and person-to-person spread among passengers.
The CDC’s stated position aligns with WHO: person-to-person transmission among Hondius passengers is “possible but unproven.”
When to Seek Medical Care
The CDC is unambiguous: “If you may have had contact with a person with Andes virus and are experiencing symptoms, contact a medical professional immediately.”
Do not wait for respiratory symptoms. The prodromal phase — fever, fatigue, muscle aches — is the window when early ICU evaluation can prevent progression to cardiopulmonary crisis. By the time shortness of breath develops, the window is closing.
If you were aboard MV Hondius at any point during its 2026 Antarctic season, or if you had close contact with a confirmed Hondius case, tell your doctor immediately. The 45-day monitoring window means new cases are still possible through late June 2026.
Source: CDC “About Andes Virus” (updated 9 May 2026) — cdc.gov/hantavirus/about/andesvirus.html. Last updated 12 May 2026.
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