Visual explainer

What is hantavirus, and why does this outbreak matter?

The virus behind the MV Hondius crisis — how it kills, how it spreads, and why the official framing may be too reassuring.

The virus

A family of viruses, spread across the globe.

Hantaviruses are rodent-borne and found worldwide. In the Americas, they cause hantavirus pulmonary syndrome — your lungs fill with fluid. In Europe and Asia, they cause hemorrhagic fever with renal syndrome — your kidneys fail.

The strain on the Hondius is the Andes virus, endemic to Argentina and Chile. It's the only hantavirus that can pass between humans — and that's why this outbreak has no precedent.

38%

of people who develop hantavirus pulmonary syndrome from the Andes virus die. Roughly one in three.

Lethality

Case fatality, in context.

The percentage of confirmed infected people who die. Higher doesn't always mean scarier — it depends on how easily the virus spreads.

Ebola (Zaire)

~66%

Andes virus

~38%

Sin Nombre

~36%

MERS

~34%

Hantaan (Asia)

~12%

SARS (2003)

~10%

COVID-19

~1%

Seasonal flu

<0.1%

Sources: CDC, WHO, published meta-analyses. COVID IFR ~0.5–1%; CFR higher in early waves.

Progression

Two phases. The second one kills.

The first phase feels like flu — easy to dismiss. Then the lungs collapse. The transition can happen in hours.

Phase 1 — Prodromal

DAYS 1–5

Fever, fatigue, muscle aches — especially thighs, hips, back. Headache, dizziness, chills. Nausea, vomiting, abdominal pain. Indistinguishable from a bad flu. This is when people are most infectious — and least likely to suspect hantavirus.

↓

Phase 2 — Cardiopulmonary crisis

DAYS 5–7+

Coughing → sudden shortness of breath as lungs fill with fluid. Blood pressure drops. Heart can't pump. ICU. Intubation. Possibly ECMO — a machine that oxygenates your blood outside your body. The lungs drown from the inside. Death comes from respiratory failure or cardiogenic shock.

↓

Recovery — if it comes

DAYS 7–14+

If the body clears the virus and the lungs hold, recovery begins — slowly. Weeks to months. No antiviral speeds this up. Survival comes down to your immune system winning the fight while ICU care buys you time.

Transmission

With every other hantavirus, infection ends with you.

You inhale dust contaminated with mouse droppings. You get sick. You can't give it to anyone. The chain stops.

Andes virus is the exception. It can pass between people during a narrow infectious window — around the day fever develops. That's what played out on the Hondius, and it's why this outbreak sits in its own category.

Precedent

Epuyén, Argentina. 2018.

Patient zero attends a birthday party with ~100 guests. He's had a fever since that morning. He stays 90 minutes. He infects five people — two at his table, two four feet away, and one who crosses his path briefly on the way to the restroom.

Patient two, 61, socially active, infects six more people before dying.

His wife attends his wake while running a fever. She infects ten more people. They fall sick 17–40 days later.

Three superspreader events. 34 infections. 11 dead. Published in the New England Journal of Medicine.

The infectious window is short — about a day. But during that day, brief indoor proximity is enough.

80+ healthcare workers were exposed without PPE. None were infected.
The ship's doctor, who provided sustained close care, was.

days. The maximum incubation period. Six weeks of carrying the virus before the first symptom appears.

Thirty passengers left St Helena on April 24 without contact tracing. We won't know they're all clear until early June.

Treatment

No approved antiviral. No widely available vaccine. No cure.

Survival depends on reaching an ICU fast enough, and on whether the body can outlast the virus with mechanical support.

Supportive ICU care

The actual lifesaver

Intubation, ventilation, vasopressors, cautious fluids. Keep the patient alive while the immune system fights. Early admission dramatically improves survival.

ECMO (heart-lung bypass)

Available at specialist centres

A machine oxygenates blood externally when lungs and heart fail. Early placement improves outcomes — requires highly specialised equipment and staff.

Ribavirin

Inconclusive

The only antiviral studied for hantavirus. Some benefit for the kidney form. Disappointing for the lung form. Significant side effects. Currently unused in standard care.

Monoclonal antibodies

Experimental — promising

Protective against lethal Andes virus in animal models. Convalescent plasma showed borderline benefit in a Chilean trial. The strongest therapeutic hope — but nothing is approved for clinical use.

Vaccines

Limited availability

Inactivated vaccines exist in China and Korea for Asian strains (~2M doses/year). Nothing approved for Andes virus. DNA candidates remain in preclinical development.

History

890 confirmed cases in thirty years. Then a cruise ship changed everything.

The first recognised outbreaks were during the Korean War in the 1950s, when thousands of UN soldiers developed hemorrhagic fever. The causative virus wasn't isolated until 1978.

In the Americas, hantavirus wasn't recognised until 1993, when young, healthy Navajo Nation members died of sudden respiratory failure in the Four Corners region. The pathogen: Sin Nombre virus — "the virus with no name."

Between 1993 and 2023, only 890 cases of HPS were confirmed in the entire United States. The virus has always been rare. But it had never been aboard a confined vessel with 175 people from 23 countries — passengers dispersing across the globe before anyone understood what was happening.

The virus was always this deadly. The ship gave it reach.