Two clinical syndromes, one virus family
Hantavirus illness comes in two distinct clinical pictures, depending on which species you're infected with. Hantavirus pulmonary syndrome (HPS) dominates in the Americas — caused by Sin Nombre, Andes and related viruses. It primarily damages the lungs. Hemorrhagic fever with renal syndrome (HFRS) dominates in Eurasia — caused by Hantaan, Seoul, Puumala and Dobrava viruses. It primarily damages the kidneys. Both share an identical opening phase that can fool clinicians into diagnosing influenza.
Phase 1 — Prodromal phase (days 1–7)
The prodrome lasts three to seven days and is indistinguishable from the flu. Patients report:
- Fever often 38–40 °C, sometimes with chills
- Severe muscle aches in thighs, hips, back and shoulders — a near-universal symptom
- Headache, often described as severe
- Fatigue and malaise
- Gastrointestinal upset — nausea, vomiting, diarrhoea, abdominal pain
- Dizziness on standing, blurred vision (especially with Puumala virus)
Phase 2 — Cardiopulmonary phase (HPS)
In the Americas, severe disease begins abruptly four to ten days after the prodrome with sudden, rapidly worsening shortness of breath. Within hours patients may require mechanical ventilation. The cardinal feature is non-cardiogenic pulmonary edema: capillary leak floods the lungs with plasma. Cardiac output drops; shock develops. Mortality at this stage is 30–50% even in well-resourced ICUs.
Phase 2 — Renal phase (HFRS)
In Eurasia, severe disease typically progresses through five textbook phases: febrile, hypotensive, oliguric, diuretic and convalescent. The hallmarks are acute kidney injury (rising creatinine, falling urine output), thrombocytopenia and hemorrhagic complications (petechial rashes, conjunctival haemorrhage, gastrointestinal bleeding). Mortality is 5–15% for Hantaan and Dobrava viruses, under 0.4% for Puumala.
Warning signs — when to seek emergency care
Anyone with possible rodent exposure who develops sudden shortness of breath, severe muscle aches with fever, declining urine output, or blood in the urine, stool or vomit should be evaluated immediately. Tell the clinician about the exposure — hantavirus is rare enough that doctors rarely consider it without prompting.