Hantavirus disease in humans typically evolves in two distinct phases, separated by a clinical tipping point that can occur within 24 to 48 hours. Recognising the early symptoms is not enough: speed of transfer to intensive care drives prognosis. Summary based on official clinical briefs from the CDC and WHO.
Incubation period: 7 to 42 days for the Andes virus
The incubation period is the interval between exposure to the virus and the onset of symptoms. It varies by hantavirus strain:
| Strain | Incubation | Clinical form |
|---|---|---|
| Andes virus | 7 to 42 days (mean 18-24) | Pulmonary syndrome (Americas) |
| Sin Nombre virus | 1 to 5 weeks | Pulmonary syndrome (North America) |
| Hantaan virus | 1 to 8 weeks | HFRS (Asia) |
| Puumala virus | 2 to 4 weeks | Moderate HFRS (Europe) |
The Andes virus has the widest range in the family. That is why French and international health authorities apply a 42-day medical surveillance to MV Hondius passengers after their last possible exposure — i.e., through late June 2026 for people disembarked on 10 May.
During this incubation, the person is not contagious. Person-to-person transmission of the Andes virus, rare, has only been described during the symptomatic phase, in close and prolonged contact (source: WHO).
Phase 1 — An initial flu-like picture
The first symptoms often appear abruptly and are non-specific:
- High fever (often above 38.5 °C) and chills
- Severe headaches
- Marked myalgia, notably in the back, thighs and shoulders
- Digestive symptoms: abdominal pain, nausea, vomiting, sometimes diarrhoea
This phase typically lasts 3 to 5 days. At this stage, no symptom clinically distinguishes hantavirus disease from severe influenza or another viral infection. Outside a known epidemic context, the diagnosis is rarely made during this initial phase.
That is precisely why health authorities ask people under MV Hondius surveillance to systematically mention their exposure to any consulting physician — even for simple fever. That information changes the management: it triggers early PCR testing and hospital surveillance.
The tipping point: pulmonary phase
Around day 4 or 5, the clinical picture can flip within hours:
- A dry cough appears, initially moderate
- Exertional shortness of breath, which may rapidly evolve to dyspnoea at rest
- A feeling of chest tightness
- Hypoxaemia (drop in blood oxygen) detectable on a pulse oximeter
The underlying mechanism is non-cardiogenic pulmonary oedema: the lung blood vessels leak fluid into the alveoli through increased permeability (a viral effect on the endothelium). On imaging, this shows as a diffuse, bilateral interstitial then alveolar infiltrate.
Critical phase: shock and respiratory failure
Without prompt management, the course can progress to a critical phase within 24 to 48 hours:
- Acute respiratory failure requiring intubation and mechanical ventilation
- Cardiogenic shock from left-ventricular failure
- More rarely, severe cardiac arrhythmias
This rapid course explains the case fatality of hantavirus pulmonary syndrome. In the United States, follow-up of 510 confirmed cases over 1993-2009 reports an overall case fatality of 35% (source: Emerging Infectious Diseases / PMC). For South American strains, the WHO indicates that case fatality in the Americas is "generally between 20 and 40%" and may reach 50% depending on context. Prognosis mainly depends on:
- The speed of diagnosis (often delayed by the non-specific initial phase)
- Transfer to intensive care before the shock phase
- Access to extracorporeal membrane oxygenation (ECMO) in the most severe forms
How is the diagnosis made?
RT-PCR: the reference test in the early phase
RT-PCR (reverse transcription followed by PCR) detects viral RNA in blood or respiratory samples. It is the test of choice during the early phase:
- Clinical sensitivity: 92.5% (study in PLOS Neglected Tropical Diseases)
- Clinical specificity: 100%
- Detection window: viral load is maximal in the first five days of symptoms
For the MV Hondius, the Andes virus was confirmed by RT-PCR on 3 May 2026. Symptomatic passengers are tested on hospital arrival; contacts are tested at the onset of any suggestive sign.
Serology: for late and retrospective diagnosis
Serology detects IgM antibodies (early response, around day 5-7) then IgG (memory response, persisting for years). It takes over from PCR when viraemia drops, and is useful for retrospective epidemiological investigations.
Typical lab profile
A suggestive blood panel in an epidemic context combines: marked thrombocytopenia (often below 100 G/L), haemoconcentration, leucocytosis with circulating immunoblasts. This triad in a known exposure context is a strong signal of suspicion.
Treatment: no specific antiviral, intensive supportive care
The WHO reminds us in its fact sheet: "there is no specific antiviral treatment or licensed vaccine against hantavirus infection". Ribavirin, used for HFRS in Asia, has not shown efficacy for pulmonary syndrome (source: CDC).
Medical management therefore rests on supportive intensive care:
Lung-protective mechanical ventilation
The patient is intubated as soon as hypoxaemia becomes severe. The ventilation strategy is called lung-protective: low tidal volume (6 ml/kg), positive end-expiratory pressure (PEEP), limited plateau pressure to avoid worsening alveolar injury.
Strict haemodynamic management
The challenge is to maintain blood pressure without worsening pulmonary oedema through excess fluid. In practice: measured fluid restriction, catecholamine support (noradrenaline) as first line.
ECMO: a resort for the most severe forms
In the most severe forms, with cardiogenic shock, veno-arterial extracorporeal membrane oxygenation (ECMO) may be used. The patient's blood is pumped out of the body, oxygenated and decarboxylated by an artificial membrane, then re-injected. The technique is heavy, but teams using early ECMO report a significant improvement in prognosis in this indication.
In France, the main ECMO centres are at AP-HP (Pitié-Salpêtrière, Saint-Louis, Bichat), in Lyon, in Marseille and in Strasbourg. That is one of the reasons French passengers repatriated from the MV Hondius were directed to Bichat, a centre equipped for ECMO.
No licensed vaccine
No vaccine is licensed in the European Union or the United States against New World hantaviruses (Andes, Sin Nombre). Inactivated vaccines against Asian strains (Hantaan, Seoul) have been produced in China and South Korea since the 1990s, but they do not protect against the Andes virus.
mRNA vaccine candidates are under study at the pre-clinical stage, but none has reached phase 3 clinical trials to date. See our dedicated article where does vaccine research stand?.
When to seek care? Warning signs
If you are under MV Hondius surveillance (repatriated passenger, identified contact via return flights from Saint Helena or Johannesburg), or you have had a likely exposure to wild rodents, the following signs should prompt you to call your local emergency services (in France: 15 or 112) without delay:
- Fever above 38 °C with body aches and headache
- Dry cough appearing during or after a febrile syndrome
- Shortness of breath, even mild
- A feeling of respiratory distress at rest
Always mention your exposure to the medical dispatcher and to the care team. That information enables specialised care.
Outside any known exposure to wild rodents or to MV Hondius passengers, these same symptoms point in the vast majority of cases to a far more common cause (influenza, common viral respiratory infection). When in doubt, talk to your GP first.