Hantavirus infections

🦠 Hantavirus infection is a rare but potentially fatal rodent-borne zoonosis. It classically causes two overlapping clinical syndromes: haemorrhagic fever with renal syndrome (HFRS), seen mainly in Europe and Asia 🌍, and hantavirus pulmonary syndrome (HPS), seen mainly in the Americas 🌎. In the UK, the main recognised concern is Seoul hantavirus, associated with wild and pet brown rats.

📖 About

• Hantaviruses are enveloped, segmented, negative-sense RNA viruses in the Hantaviridae family, particularly the genus Orthohantavirus.
• The natural reservoirs are usually rodents, including rats, mice and voles, which shed virus in urine, faeces and saliva.
• Humans are usually infected by inhaling aerosolised contaminated dust, especially when cleaning sheds, barns, rodent-infested rooms or cages.
• Clinical disease ranges from mild febrile illness to AKI with haemorrhage or severe capillary leak with pulmonary oedema.
• Case fatality varies widely: Puumala infection in Europe is usually much milder, while HPS due to New World hantaviruses can have high mortality.

🦠 Aetiology & Transmission

• Main route: inhalation of dust contaminated by infected rodent urine, droppings or saliva.
• Less common routes include direct contact with mucous membranes, broken skin, or rodent bites.
• Rodents are usually asymptomatic carriers and may shed virus for prolonged periods.
• Most hantaviruses do not spread person-to-person.
• Important exception: Andes virus in South America can rarely spread between people after close or prolonged contact.
• At-risk groups include farmers, forestry workers, pest-control workers, military personnel, laboratory staff, cleaners of rodent-infested spaces, and pet rat owners.

🇬🇧 UK Context

• Hantavirus infection is rare in the UK.
• The strain most relevant to the UK is Seoul hantavirus, carried by Rattus norvegicus - the brown rat.
• Cases have been linked to both wild rats and pet rats.
• Seoul hantavirus usually causes an HFRS-like illness, but severity varies from mild flu-like disease to AKI and haemorrhagic features.
• Andes virus has not been detected in UK rodents; UK public risk from person-to-person spread remains very low.
• Good cage hygiene, handwashing after handling rats, and avoiding inhalation of dried bedding/droppings are key prevention measures.

🌍 Major Viruses & Geography

• Haantan virus → East Asia, especially China, Korea and parts of Russia. Causes more severe HFRS.
• Puumala virus → Scandinavia, Northern and Western Europe, and Russia. Causes nephropathia epidemica, usually a milder HFRS.
• Dobrava-Belgrade virus → Balkans and parts of Europe. Can cause severe HFRS.
• Seoul virus → Worldwide, carried by brown rats. Relevant to UK wild and pet rat exposure.
• Sin Nombre virus → North America, especially the south-western USA. Important cause of HPS.
• Andes virus → South America. Causes severe HPS and is the main hantavirus known to spread person-to-person.

🩺 Clinical Presentation

• Incubation: usually 1–5 weeks, but may range from a few days to several weeks after exposure.
• Early prodrome: fever, chills, severe myalgia, headache, dizziness, nausea, vomiting, abdominal pain and malaise.
• HFRS pattern: fever → hypotension/shock → oliguria/AKI → diuresis → recovery.
• HFRS features: AKI, proteinuria, haematuria, thrombocytopenia, conjunctival suffusion, petechiae or other bleeding features.
• HPS pattern: febrile prodrome followed by cough, dyspnoea, rapidly progressive non-cardiogenic pulmonary oedema and shock.
• HPS can deteriorate quickly, often resembling severe sepsis or ARDS.

🧬 Pathophysiology

• Hantaviruses infect vascular endothelial cells but do not usually cause direct endothelial destruction.
• The major problem is immune-mediated endothelial dysfunction, causing capillary leak.
• In HFRS, capillary leak and inflammation particularly affect the kidneys, causing AKI, proteinuria and haemorrhagic features.
• In HPS, pulmonary capillary leak causes rapid pulmonary oedema, hypoxia and shock.
• This is why careful fluid management is crucial: too much fluid may worsen pulmonary oedema, but under-resuscitation may worsen shock and renal injury.

❓ Differentials

• Leptospirosis, especially Weil’s disease.
• Sepsis with AKI or ARDS.
• Other viral haemorrhagic fevers, depending on travel history.
• Influenza, COVID-19 and other viral pneumonias.
• Malaria in returning travellers.
• Acute glomerulonephritis or vasculitis with AKI.
• Rickettsial infection, dengue or other travel-related febrile illnesses.

🧪 Investigations

• FBC: thrombocytopenia, leukocytosis and raised haematocrit from haemoconcentration.
• U&E: raised creatinine and urea in HFRS; monitor potassium and acid-base status.
• Urinalysis: proteinuria and haematuria are common in renal disease.
• LFTs: mild transaminitis may occur.
• Coagulation screen: assess bleeding risk and DIC-like picture.
• CRP / cultures: useful because bacterial sepsis is an important mimic.
• CXR / CT chest: interstitial oedema or pulmonary oedema in HPS.
• ABG/VBG: hypoxia, lactate and acid-base status in severe disease.
• Confirmation: hantavirus serology, usually IgM/IgG, and/or PCR depending on timing and specialist lab availability.
• In the UK, discuss suspected cases with local microbiology/virology, infectious diseases and UKHSA pathways where appropriate.

💊 Management

• Treatment is mainly supportive; there is no widely licensed specific antiviral treatment for routine use.
• Early senior input is important: involve infectious diseases, microbiology/virology, renal and critical care depending on presentation.
• HPS: oxygen, high-dependency/ICU monitoring, ventilatory support if needed, and cautious fluid management.
• HFRS: careful fluid balance, electrolyte correction, blood pressure support and renal replacement therapy if indicated.
• Ribavirin may have a role in some severe early HFRS cases in specialist settings, but it has not shown clear benefit for HPS.
• Avoid excessive IV fluids in suspected HPS because pulmonary capillary leak can worsen rapidly.
• Use appropriate infection prevention precautions, especially if Andes virus exposure is possible or the patient has severe respiratory disease.

🛡️ Prevention

• Control rodent infestations and seal access points in homes, sheds and workplaces.
• Do not sweep or vacuum dry rodent droppings, as this may aerosolise virus-containing dust.
• Ventilate enclosed spaces before cleaning.
• Wear gloves and consider a suitable mask/respirator when cleaning heavily contaminated areas.
• Dampen droppings and nesting material with disinfectant before removal.
• Wash hands after handling pet rats, cages, bedding or contaminated equipment.
• Store food securely and dispose of waste properly to reduce rodent attraction.

📌 Clinical Pearls

• Think of hantavirus in fever + thrombocytopenia + AKI after rodent exposure.
• Think of HPS in fever + thrombocytopenia + rapidly progressive pulmonary oedema, especially after travel to the Americas.
• In the UK, remember Seoul hantavirus in patients with pet rat or wild rat exposure and unexplained febrile AKI.
• HPS shock is driven largely by capillary leak, not simply vasodilation, so fluid resuscitation must be careful and reassessed frequently.
• Most hantavirus infections are not contagious between people; Andes virus is the major exception.

🚨 Current Note: Andes Virus Cluster, 2026

• In 2026, WHO, ECDC and UKHSA reported a multi-country cluster of hantavirus illness linked to cruise-ship travel and exposure in South America.
• The concern was Andes virus, which can cause severe HPS and can rarely spread between people after close contact.
• Public health advice emphasised that the wider public risk remained low, but exposed travellers required monitoring and follow-up.
• This does not mean hantavirus is spreading widely in the UK; the UK situation remains mainly about rare Seoul virus infection from rat exposure.

📚 References

• UKHSA: Hantavirus symptoms, transmission and UK risk.
• CDC: Clinical overview of hantavirus and HPS.
• WHO: Hantavirus fact sheet and 2026 outbreak updates.
• ECDC: Orthohantavirus infection factsheet and 2026 cluster assessment.
• ICTV: Hantaviridae taxonomy.