What Is Hantavirus? A Plain-English Guide to the 2026 Outbreak

On May 4, 2026, the World Health Organization issued Disease Outbreak News notification DON-599, confirming a multi-country cluster of hantavirus cases linked to the cruise ship MV Hondius. By the time the alert reached the public, three passengers had already died and more than a dozen countries were tracing contacts. If you've never heard of hantavirus before, you are not alone — and you are not late.

This guide is what we wish was easy to find when the outbreak began: a plain-English overview of the virus, the diseases it causes, why the Andes strain at the center of the 2026 outbreak is unusual, and what ordinary precautions actually matter. It is written for general readers and reviewed by a clinician.

1. The basics: what is a hantavirus?

Hantaviruses are a genus of enveloped, single-stranded RNA viruses in the family Hantaviridae. They were first identified by Dr. Ho Wang Lee in 1976, who isolated the namesake Hantaan virus from striped field mice near the Hantan River in Korea. Since then, researchers have catalogued more than two dozen distinct hantaviruses worldwide, each typically associated with a specific rodent host that carries the virus without becoming sick.

From a public-health perspective, the strains divide into two clinical groups: those that cause hemorrhagic fever with renal syndrome (HFRS), seen mostly in Eurasia, and those that cause hantavirus pulmonary syndrome (HPS), seen mostly in the Americas. We'll come back to these.

2. How does it usually spread?

The classical transmission route is environmental: a wild rodent — a deer mouse in North America, a long-tailed pygmy rice rat in Patagonia, a striped field mouse in East Asia — sheds virus in its urine, droppings, or saliva. When that material dries and is disturbed (sweeping out a cabin, opening up a long-shut shed, cleaning a rodent-infested attic), microscopic particles aerosolize and a person inhales them.

Bites are rare. Surfaces matter only when freshly contaminated. The virus does not spread through mosquitoes, food chains, or normal respiratory exposure between healthy people. One exception matters in 2026: the Andes virus (ANDV) is the only hantavirus documented to occasionally pass directly from one person to another through close, prolonged contact — which is why the MV Hondius cluster has the attention of every public-health agency in the world.

What we don't know yet about MV Hondius

As of this writing, investigators are still confirming whether person-to-person transmission occurred on the ship or whether all cases trace to a common environmental exposure during the South American leg of the cruise. The case-counting is live on our tracker and is updated against official WHO and ECDC notifications.

3. The two diseases hantaviruses cause

The MV Hondius outbreak is HPS, caused by the Andes strain. HPS is what most English-language coverage means when it says "hantavirus." The illness has a deceptively gentle prodrome — fever, muscle aches, sometimes vomiting and diarrhea — and then, between days four and ten, fluid abruptly floods the lungs. Patients who reach an ICU early have far better odds than those who don't.

4. The strains in plain terms

• Sin Nombre virus — the strain identified in the 1993 Four Corners outbreak in the southwestern United States. Reservoir: deer mouse (Peromyscus maniculatus). Cause of most US HPS cases.
• Andes virus (ANDV) — confined to South America in its reservoir distribution. Reservoir: long-tailed pygmy rice rat (Oligoryzomys longicaudatus). The only hantavirus with documented person-to-person transmission, mostly in close-contact household clusters.
• Hantaan, Seoul, Puumala, Dobrava — Eurasian strains, mostly cause HFRS rather than HPS. Seoul virus circulates worldwide via the Norway rat, including in port cities.

5. Symptoms timeline

After an incubation period of 1 to 8 weeks (most commonly 2 to 4), symptoms appear in two phases:

1. Phase 1 (days 1–7), febrile prodrome. Fever, muscle aches, fatigue, sometimes nausea, vomiting, abdominal pain. Easy to mistake for influenza or food poisoning.
2. Phase 2 (days 4–10), cardiopulmonary phase. Sudden shortness of breath, fast breathing, low blood pressure, dropping oxygen levels. This is the dangerous window.

If you have been on or near the MV Hondius's recent itinerary or in close contact with a confirmed case and you develop fever with any respiratory symptom, contact your local health authority immediately and mention the exposure. There is no specific antiviral cure; outcomes hinge on getting to an ICU early.

6. How to protect yourself

• Avoid contact with rodents and their droppings; never sweep dry droppings.
• Before cleaning an enclosed space that may have been infested, ventilate it for at least 30 minutes.
• Wet-clean with a dilute bleach solution (1:10), wear nitrile gloves, and use an N95-equivalent respirator if heavy contamination is present.
• Travelers in rural South America should avoid sleeping in shelters with visible rodent activity and store food in sealed containers.
• For close contacts of a confirmed Andes-virus case: monitor for fever for 45 days and follow your public-health authority's guidance.

7. Should you be worried?

WHO currently assesses the global risk as low. Hantaviruses do not spread efficiently between people the way influenza or SARS-CoV-2 do; they cannot start a respiratory pandemic the way coronaviruses can. What hantaviruses can do is kill a meaningful fraction of the small number of people they reach — which is why this outbreak deserves serious attention from health agencies even though it does not deserve panic from the public.

We'll keep this article current as the situation evolves. For the latest case counts, country breakdowns and source documents, use the live tracker on the homepage or read the next explainer in this series: Andes virus, the strain at the center of MV Hondius.

Frequently asked questions

Is hantavirus contagious between people?

Almost never. The Andes virus is the rare exception, and even then person-to-person spread happens mostly in households with prolonged, close contact.

Is there a vaccine?

No vaccine is approved in the European Union or the United States. Several candidates have entered early clinical trials. Some Eurasian countries deploy locally developed vaccines for HFRS strains, with limited published efficacy data.

Can you survive hantavirus?

Yes — most patients survive with aggressive supportive care in an ICU. Reported case-fatality is roughly 30–40% for ANDV-caused HPS, meaning the majority of identified cases recover. Mild cases that never reach a hospital are likely undercounted.