Hantavirus Infection: Symptoms, Causes & Treatment

What Is Hantavirus Infection?

Hantavirus infection is a viral illness caused by hantaviruses, which are spread by rodents. The infection primarily affects the kidneys and can cause hemorrhagic fever with renal syndrome (HFRS). In Europe, the milder form called nephropathia epidemica is caused by the Puumala virus carried by bank voles.

Hantaviruses belong to a family of viruses found worldwide, with different species causing illness in different regions. These viruses naturally infect rodents without causing disease in them, but can cause serious illness when transmitted to humans. The type of hantavirus and the severity of illness depends on the rodent species carrying it and the geographic region.

In Europe, the primary concern is the Puumala virus, which causes a relatively mild form of disease called nephropathia epidemica. This virus is carried by the bank vole, a common small rodent found in forests and rural areas throughout northern and central Europe. The disease is most prevalent in Scandinavia, Finland, Russia, and parts of Germany and France, with thousands of cases reported annually.

In the Americas, different hantaviruses cause hantavirus pulmonary syndrome (HPS), a more severe disease affecting the lungs rather than the kidneys. The Sin Nombre virus, carried by deer mice, is the most common cause in North America. HPS has a significantly higher mortality rate than the European form, making geographic awareness important for understanding risk.

In Asia, particularly in China, Korea, and Russia, the Hantaan virus and Seoul virus cause classic hemorrhagic fever with renal syndrome. These forms tend to be more severe than nephropathia epidemica but less severe than hantavirus pulmonary syndrome. The Seoul virus is notable for being carried by the common rat, which has spread it to urban areas worldwide.

Understanding the Disease Names

The terminology around hantavirus infections can be confusing because the disease has been known by various names throughout history and across different regions. Hemorrhagic fever with renal syndrome (HFRS) is the umbrella term used by the World Health Organization to describe hantavirus infections that primarily affect the kidneys. This includes several disease variants with different severity levels.

Nephropathia epidemica specifically refers to the milder form of HFRS caused by Puumala virus in Europe. The name means "epidemic kidney disease" and reflects the characteristic kidney involvement. Some older literature may refer to this condition as "epidemic nephropathy" or simply by regional names.

The disease was historically known as Korean hemorrhagic fever after it was first characterized during the Korean War in the 1950s, when thousands of United Nations troops became ill. It took decades of research before the causative virus was isolated and named Hantaan virus after the Hantan River in South Korea.

Who Is at Risk?

Certain populations face higher risk of hantavirus infection due to their activities or living situations. People who work or spend leisure time in areas with rodent populations are at greatest risk, particularly when these activities involve disturbing accumulated rodent waste.

Rural residents living in or near forested areas endemic for hantavirus face ongoing exposure risk. Farmers, forestry workers, and those maintaining vacation properties in wooded areas should be particularly aware of prevention measures. The risk is highest during years when rodent populations surge, which typically follows abundant food supplies from mast years (when trees produce exceptionally large seed crops).

Occupational exposure affects construction workers, pest control professionals, cleaning staff, and utility workers who may encounter rodent-infested buildings or areas. Military personnel conducting field exercises and researchers working with wild rodents also face elevated risk.

What Are the Symptoms of Hantavirus Infection?

Symptoms of hantavirus infection typically appear 1-3 weeks after exposure and include sudden high fever, severe headache, muscle pain (especially in the back and abdomen), nausea, and blurred vision. A hallmark sign is decreased urine output as the kidneys become affected. Most symptoms resolve within 1-2 weeks with proper care.

The onset of hantavirus infection is typically abrupt, with patients often able to identify the exact day symptoms began. This sudden presentation helps distinguish it from other viral illnesses that may develop more gradually. The initial phase is dominated by non-specific symptoms that can mimic many other conditions, making early diagnosis challenging.

The febrile phase begins with sudden high fever, often exceeding 38.5°C (101.3°F), accompanied by severe headache and general malaise. Patients frequently report intense muscle pain, particularly affecting the back, abdomen, and thighs. This myalgia can be severe enough to mimic surgical conditions, leading some patients to emergency departments with suspected appendicitis or kidney stones.

Gastrointestinal symptoms are common during this early phase, including nausea, vomiting, and abdominal pain. The abdominal discomfort may be diffuse or localized to the flanks, reflecting early kidney involvement. Diarrhea is less common but can occur. Some patients also experience facial flushing and conjunctival injection (red eyes) during this phase.

Visual disturbances affect a significant proportion of patients and can be an important diagnostic clue. Blurred vision and difficulty focusing, often described as myopia or near-sightedness, result from fluid shifts affecting the lens. Some patients also experience photophobia or reduced color vision.

Kidney-Related Symptoms

As the disease progresses into the oliguric phase, kidney involvement becomes apparent through changes in urination. Patients may notice a marked decrease in urine output, sometimes producing less than 400 milliliters per day. This oliguria typically lasts 3-7 days and results from the virus's effect on kidney blood vessels and filtering function.

Flank pain and lower back discomfort intensify during this phase as kidney inflammation peaks. Patients may experience tenderness when pressure is applied to the kidney areas. Some develop visible blood in urine (hematuria), though microscopic blood is more common. The combination of reduced urine output, back pain, and fever should prompt consideration of hantavirus infection in endemic areas.

The diuretic phase follows, during which kidney function begins to recover and urine output dramatically increases. Patients may produce several liters of urine daily during this phase, which typically lasts 1-2 weeks. This polyuria reflects the kidneys' recovery but requires careful fluid management to prevent dehydration and electrolyte imbalances.

Complete convalescence may take several weeks to months, with some patients reporting persistent fatigue, difficulty concentrating, and reduced exercise tolerance. However, long-term kidney damage is rare, and most patients recover full renal function without permanent complications.

Severe Complications

While most cases of nephropathia epidemica are mild to moderate, some patients develop severe complications requiring intensive care. Acute kidney injury severe enough to require dialysis occurs in approximately 5-10% of hospitalized patients. This temporary kidney failure results from the virus damaging the blood vessels within the kidneys, leading to impaired filtration and fluid retention.

Hemorrhagic manifestations can occur, including bleeding gums, nosebleeds, and petechiae (small red spots from bleeding under the skin). These result from low platelet counts and blood vessel damage caused by the virus. Severe hemorrhage is uncommon in the European form but more frequent in Asian variants of the disease.

Neurological complications, though rare, have been reported and include encephalitis, seizures, and pituitary involvement leading to hormonal disturbances. Cardiac complications such as myocarditis and rhythm disturbances can occur but are uncommon. These severe manifestations typically affect older patients or those with underlying health conditions.

How Does Hantavirus Spread?

Hantavirus spreads primarily through inhaling airborne particles from rodent urine, droppings, or saliva. Common exposure scenarios include cleaning areas where rodents have nested, such as cabins, sheds, and basements. The virus can remain infectious in dried material for several weeks. Importantly, hantavirus does not spread from person to person.

Understanding how hantavirus transmission occurs is essential for effective prevention. The virus is shed in large quantities in the urine, feces, and saliva of infected rodents. When these materials dry, viral particles can become airborne during activities that disturb them, creating an infectious aerosol that can be inhaled.

The most common route of infection is inhalation of contaminated dust. This typically occurs when people clean buildings that have been vacant for extended periods, particularly summer cabins, vacation homes, or outbuildings that provide shelter for rodents during winter. Sweeping, vacuuming, or moving stored materials can aerosolize dried rodent waste, making the virus particles airborne.

Direct handling of rodents, whether alive or dead, presents another transmission route. Researchers, pest control workers, and individuals removing rodents from traps may be exposed through direct contact. Even brief handling without gloves can result in transmission, particularly if the virus-contaminated material contacts mucous membranes or broken skin.

Contaminated food and water can also transmit hantavirus, though this is less common than airborne transmission. Rodents that access food storage areas can contaminate items with urine or feces. Consuming contaminated food or water without proper cleaning or cooking can lead to infection.

Rodent bites, while uncommon, can transmit the virus directly through saliva. This route primarily affects researchers or individuals handling live rodents. The bite wound provides direct access for viral particles to enter the bloodstream.

Environmental Persistence

Hantaviruses can survive in the environment for extended periods under favorable conditions, though they are ultimately quite fragile compared to many other pathogens. Understanding this persistence helps inform cleaning and decontamination protocols.

In dried rodent waste protected from sunlight and heat, the virus can remain infectious for 2-3 weeks or longer. Cool, moist, and shaded environments favor viral survival, while direct sunlight, heat, and desiccation rapidly inactivate the virus. Indoor environments where rodent waste accumulates, such as attics and storage areas, may maintain infectious virus longer than outdoor settings.

The virus is readily inactivated by common disinfectants, including dilute bleach solutions, alcohol-based sanitizers, and most household cleaning products. Proper cleaning with appropriate disinfectants effectively eliminates viral contamination from surfaces.

Rodent Carriers

Different hantavirus strains are carried by specific rodent species, which determines the geographic distribution of disease. Understanding which rodents carry hantavirus in your region helps assess risk and target prevention efforts.

In Europe, the bank vole (Myodes glareolus) is the primary carrier of Puumala virus. This small, reddish-brown rodent inhabits forests, woodland edges, and rural areas throughout northern and central Europe. Bank voles do not typically enter buildings but may shelter in outbuildings, woodpiles, and vacation cabins.

In North America, the deer mouse (Peromyscus maniculatus) carries the Sin Nombre virus responsible for hantavirus pulmonary syndrome. This mouse species is widespread across rural and semi-rural areas. White-footed mice, cotton rats, and rice rats carry other pathogenic hantaviruses in different regions of the Americas.

The Norway rat and roof rat carry the Seoul virus, which has achieved worldwide distribution following the global spread of these commensal rodents. Unlike many other hantaviruses, Seoul virus can therefore cause urban outbreaks wherever rats are present.

When Should You Seek Medical Care?

Seek medical care if you develop high fever, severe headache, back pain, and decreased urination after potential rodent exposure. Contact a healthcare provider promptly if symptoms develop within 1-6 weeks of cleaning buildings, handling rodents, or activities in rodent-populated areas. Seek emergency care for breathing difficulty, severe bleeding, or inability to urinate.

Early medical evaluation is important for suspected hantavirus infection, even though there is no specific antiviral treatment. Prompt diagnosis allows for appropriate supportive care, monitoring for complications, and public health notification that may benefit others at risk from the same exposure source.

Contact a healthcare provider if you develop flu-like symptoms within 1-6 weeks of activities involving potential rodent exposure. Key symptoms warranting evaluation include sudden onset of high fever, severe headache, and muscle pain, particularly when combined with back or abdominal pain and changes in urination.

Be sure to inform your healthcare provider about recent activities that may have involved rodent exposure. Mention if you have recently cleaned cabins, sheds, or basements; worked in areas with known rodent activity; handled live or dead rodents; or spent time in rural or forested areas endemic for hantavirus.

Medical assessment will typically include blood tests to check kidney function and platelet counts, along with specific serological tests for hantavirus antibodies. Early detection of kidney involvement allows for appropriate fluid management and monitoring.

How Can You Prevent Hantavirus Infection?

Prevent hantavirus infection by avoiding rodent exposure and using proper protection when cleaning potentially contaminated areas. Key measures include using FFP3 respirator masks and wet cleaning methods (never sweeping or vacuuming), wearing disposable gloves, ventilating spaces before entering, and rodent-proofing buildings. These precautions are especially important when opening vacation homes or cleaning outbuildings.

Prevention of hantavirus infection centers on two main strategies: reducing rodent populations around living spaces and protecting yourself when exposure to rodent-contaminated areas is unavoidable. Both approaches are important for comprehensive protection.

Safe Cleaning Procedures

When cleaning areas with potential rodent contamination, following proper procedures significantly reduces infection risk. These precautions are particularly important when opening vacation homes, cleaning outbuildings, or working in areas known to have rodent activity.

Before entering a building that has been closed or shows signs of rodent activity, ventilate the space thoroughly. Open all doors and windows and leave the area for at least 30 minutes to allow fresh air to disperse any airborne viral particles. If possible, cross-ventilate by opening windows on opposite sides of the building.

Wear appropriate personal protective equipment when cleaning contaminated areas. An FFP3 (or N95) respirator mask provides effective protection against inhaling viral particles – cloth masks or surgical masks are not adequate for this purpose. Disposable rubber or plastic gloves protect hands from direct contact with contaminated materials.

Never sweep or vacuum areas with rodent droppings, as these actions aerosolize dried waste and dramatically increase inhalation risk. Instead, use wet cleaning methods exclusively. Spray all visible droppings, urine stains, and nesting materials with disinfectant solution before disturbing them. A mixture of 1 part bleach to 10 parts water, or a commercial disinfectant, is effective.

Allow the disinfectant to soak for at least 5-10 minutes before cleaning up. Then use damp paper towels or disposable cloths to wipe up the contaminated material. Place all cleaning materials, gloves, and collected waste in a sealed plastic bag before disposal in an outdoor trash container.

After removing protective equipment, wash hands thoroughly with soap and water. Shower and change clothes after extensive cleaning work in contaminated areas. Launder clothes separately in hot water.

Rodent Control

Reducing rodent populations and preventing their access to living spaces provides long-term protection against hantavirus exposure. Integrated pest management approaches that combine exclusion, sanitation, and targeted control are most effective.

Seal entry points to buildings that rodents might use for access. Mice can enter through gaps as small as 6mm (1/4 inch), so careful inspection and sealing of cracks, holes, and gaps around foundations, pipes, vents, and doors is important. Use steel wool, hardware cloth, or caulk to seal openings.

Eliminate food sources that attract rodents. Store food in rodent-proof containers (glass, metal, or heavy plastic). Clean up spilled food promptly. Keep pet food in sealed containers and don't leave pet food out overnight. Secure garbage in covered bins. Remove fallen fruit from around trees.

Reduce harborage areas around buildings. Keep grass and vegetation trimmed near foundations. Stack firewood at least 20 feet from buildings and elevate it off the ground. Remove debris piles, old equipment, and unused materials that provide rodent shelter. Clean up fallen seeds around bird feeders.

Consider trapping in areas with rodent activity. Snap traps baited with peanut butter are effective for mice. Check traps frequently and dispose of dead rodents using gloved hands and double bagging. Avoid using poison baits in areas where children, pets, or non-target wildlife might be affected.

How Is Hantavirus Infection Diagnosed?

Hantavirus infection is diagnosed through blood tests detecting specific antibodies (IgM and IgG) against the virus, combined with clinical symptoms and exposure history. Laboratory findings typically show low platelet count, elevated creatinine indicating kidney involvement, and protein in the urine. PCR tests can detect viral genetic material in blood during early infection.

Diagnosing hantavirus infection requires combining clinical assessment, exposure history, laboratory tests, and specific serological testing. Because early symptoms are non-specific, maintaining clinical suspicion in endemic areas or after known rodent exposure is crucial for timely diagnosis.

The clinical presentation provides important diagnostic clues. The combination of sudden fever, headache, myalgia, abdominal/back pain, and reduced urine output in a patient with potential rodent exposure strongly suggests hantavirus infection. Visual disturbances and characteristic kidney involvement help distinguish it from other febrile illnesses.

A detailed exposure history is essential. Healthcare providers should ask about activities in the 1-6 weeks before symptom onset, including cleaning buildings, handling rodents, outdoor work or recreation in endemic areas, and any observed rodent activity in living or working spaces.

Laboratory Tests

Standard laboratory tests reveal characteristic abnormalities that support the diagnosis and help monitor disease progression. These tests also guide treatment decisions and help detect complications.

Complete blood count typically shows thrombocytopenia (low platelet count), which is one of the most consistent findings in hantavirus infection. Platelet counts may fall below 100,000/microliter, sometimes severely. White blood cell counts may be elevated or normal. Mild anemia can develop as the disease progresses.

Kidney function tests demonstrate elevated serum creatinine and blood urea nitrogen, reflecting acute kidney injury. The degree of elevation correlates with disease severity. Proteinuria (protein in urine) is common and may be substantial. Urinalysis often shows red blood cells and protein.

Liver function tests may show mild elevations in liver enzymes. Electrolyte abnormalities can occur, particularly during the diuretic recovery phase when large urine volumes can cause dehydration and electrolyte losses.

Specific Diagnostic Tests

Serological testing provides definitive diagnosis by detecting antibodies against hantavirus. IgM antibodies appear early in infection (usually by symptom onset) and indicate recent or acute infection. IgG antibodies develop later and persist long-term, indicating past infection. Most laboratories use enzyme-linked immunosorbent assay (ELISA) methods.

PCR testing can detect viral RNA in blood during early infection, before antibodies develop. However, viremia (virus in blood) is typically brief, so PCR is most useful in the first week of illness. A negative PCR result does not exclude hantavirus infection if obtained later in the disease course.

Testing can often identify the specific hantavirus strain involved, which has implications for understanding the source and severity. Different laboratory methods have varying sensitivity for different viral strains.

How Is Hantavirus Infection Treated?

There is no specific antiviral treatment for hantavirus infection. Treatment is supportive, focusing on maintaining fluid balance, managing kidney function, and relieving symptoms. Most patients recover with rest, hydration, and symptomatic care. Severe cases may require hospitalization for intravenous fluids, monitoring, and temporary dialysis if kidney failure occurs.

Management of hantavirus infection relies on supportive care tailored to disease severity and phase. While there is no medication that directly kills the virus, appropriate supportive treatment allows the immune system to clear the infection while preventing complications.

Mild to Moderate Cases

Patients with mild disease can often be managed at home with close monitoring. Treatment focuses on rest, maintaining adequate hydration, and controlling symptoms. Patients should avoid strenuous activity during acute illness and recovery.

Fluid management is crucial throughout the illness. During the early phase, maintaining hydration supports kidney function. However, excessive fluid intake should be avoided as it may worsen edema if kidneys are impaired. During the diuretic phase, patients may need increased fluid intake to compensate for large urine volumes.

Symptomatic treatment includes acetaminophen (paracetamol) for fever and pain relief. Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen should generally be avoided because they may worsen kidney function and increase bleeding risk. Antiemetics can help control nausea and vomiting.

Regular monitoring of symptoms and urine output helps detect deterioration. Patients should seek medical attention if urine output decreases significantly, symptoms worsen, or new symptoms develop. Regular follow-up may include blood tests to monitor kidney function and platelet counts.

Severe Cases and Hospitalization

Patients with severe disease or significant kidney impairment typically require hospitalization. Inpatient care allows for close monitoring, intravenous fluid administration, and intervention for complications.

Intravenous fluids allow precise control of hydration status, which is particularly important when oral intake is limited by nausea or when kidney function is significantly impaired. Fluid administration must be carefully balanced to maintain adequate perfusion without causing fluid overload.

Dialysis may be required for patients with severe acute kidney injury. This typically involves hemodialysis to remove waste products and excess fluid when kidney function is inadequate. Dialysis is usually temporary, with most patients recovering sufficient kidney function to discontinue treatment within days to weeks.

Supportive measures for severe cases may include blood transfusions for significant anemia or bleeding, management of electrolyte imbalances, and respiratory support if pulmonary involvement occurs. Intensive care unit admission may be necessary for patients with multi-organ involvement or hemodynamic instability.

Recovery and Follow-up

Most patients recover fully from hantavirus infection, though complete recovery may take weeks to months. Fatigue and reduced exercise tolerance are common during convalescence. Patients should gradually increase activity as tolerated and avoid strenuous exertion until fully recovered.

Follow-up blood tests to confirm normalization of kidney function and platelet counts are typically recommended. Most patients achieve full recovery of kidney function, though some may have minor persistent abnormalities on testing. Long-term kidney damage is rare with appropriate supportive care.

Patients who recover from hantavirus infection develop lasting immunity to the specific virus strain. However, different hantavirus strains provide limited cross-protection, so reinfection with different strains remains possible in theory.

What Is the Outlook for Hantavirus Infection?

The prognosis for hantavirus infection varies by viral strain but is generally good for nephropathia epidemica. The European form (Puumala virus) has a mortality rate below 0.1%, with most patients recovering fully within 1-2 weeks. Complete kidney recovery is typical, though fatigue may persist for weeks. Hantavirus pulmonary syndrome in the Americas has higher mortality (up to 38%).

Understanding the expected course and outcomes of hantavirus infection helps patients and families know what to expect and when to be concerned about unusual developments. The prognosis varies significantly based on the specific virus involved and the severity of initial presentation.

For nephropathia epidemica caused by Puumala virus, the outlook is excellent. Mortality is very low, well under 1%, and most deaths occur in elderly patients or those with significant underlying health conditions. The vast majority of patients recover completely without permanent complications.

Recovery time varies but most patients feel substantially better within 1-2 weeks of symptom onset. However, full recovery may take longer. Fatigue, weakness, and reduced exercise tolerance commonly persist for several weeks and occasionally months. Gradual return to normal activities is recommended rather than pushing too hard too soon.

Kidney function typically recovers completely, though recovery may take weeks. Follow-up testing usually shows normalization of creatinine and urine findings. Permanent kidney damage is rare but has been reported in severe cases, particularly those requiring dialysis.

Some patients report persistent symptoms during convalescence, sometimes called post-hantavirus syndrome. These may include headaches, difficulty concentrating, joint pain, and visual changes. These symptoms typically improve gradually over months.

The outlook for hantavirus pulmonary syndrome in the Americas is more serious, with mortality rates historically around 35-40%, though improved recognition and supportive care have reduced this somewhat. Survivors typically recover without long-term pulmonary complications.