Symptoms and clinical course
Hantavirus pulmonary syndrome (HPS) has an incubation period of 1-6 weeks (typically 2-3 weeks) and progresses through three clinical phases — prodromal, cardiopulmonary, and diuretic/convalescent. Early symptoms are non-specific and often mistaken for influenza, which makes the abrupt transition into respiratory failure especially dangerous.
Prodromal phase (days 1-5)
Patients present with high fever (typically 38.5-40°C), severe myalgia of the large muscle groups (thighs, hips, back, shoulders), chills, headache and gastrointestinal symptoms — nausea, vomiting, abdominal pain and diarrhea. Cough and dyspnea are usually absent at this stage. A normal chest X-ray and the absence of upper respiratory symptoms (no sore throat, no runny nose) are key clues that distinguish the prodrome from common viral illness. Laboratory findings frequently include thrombocytopenia, left-shifted leukocytosis with atypical lymphocytes (immunoblasts), elevated hematocrit due to hemoconcentration, and elevated LDH.
Cardiopulmonary phase (days 5-10)
The transition from prodrome to cardiopulmonary phase can occur within hours. Patients develop progressive cough and dyspnea, followed by non-cardiogenic pulmonary edema as endothelial permeability collapses. Cardiogenic shock — characterized by low cardiac index and high systemic vascular resistance, unlike the high-output picture of septic shock — is the leading cause of death. Approximately 80% of patients require mechanical ventilation, and 30-40% require vasopressor support. Mortality is concentrated in the first 48 hours of this phase.
Diuretic and convalescent phase
Survivors enter a rapid diuretic phase, often producing several liters of urine per day as capillary leak resolves. Convalescence is typically slow — fatigue, exertional dyspnea and reduced exercise tolerance can persist for months. Some survivors have measurable reductions in diffusion capacity (DLCO) for up to a year. Cognitive and neuropsychiatric sequelae are increasingly reported and warrant follow-up.
ANDV-specific features
Andes virus illness frequently includes a hemorrhagic component — petechiae, conjunctival injection and overt thrombocytopenic bleeding — which is uncommon with Sin Nombre virus in North America. Renal involvement, while less prominent than in HFRS, is more common than with Sin Nombre. Person-to-person transmission of ANDV means clinicians should consider hantavirus in patients with compatible illness who have been close contacts of a confirmed case, even without rodent exposure.
When to seek care
Anyone with fever and severe myalgia who has had recent rodent exposure (rural cabins, woodsheds, grain storage, hiking in endemic areas) or contact with a confirmed hantavirus case should seek medical attention immediately. The window between prodrome and life-threatening pulmonary edema can be less than 24 hours. Tell your clinician about the exposure — hantavirus is rare and easy to miss without history.
- •Incubation 1-6 weeks, typically 2-3 weeks
- •Prodrome looks like flu but without upper respiratory symptoms
- •Thrombocytopenia + hemoconcentration + immunoblasts is the classic triad
- •Cardiopulmonary collapse can occur within hours
- •ANDV often has a hemorrhagic component absent from Sin Nombre cases
FAQ
How long after exposure do symptoms appear?+
Most patients develop symptoms 2 to 3 weeks after exposure, though the range is 1 to 6 weeks.
Can hantavirus look like COVID-19 or influenza?+
The prodrome can mimic influenza, but hantavirus typically lacks sore throat and rhinorrhea, and progresses much faster to pulmonary edema. Thrombocytopenia and hemoconcentration on labs are major clues.
Are children affected the same way?+
Children can develop HPS, including with ANDV. Disease tends to be slightly less severe in young children than in adults, but mortality remains high.