Pandemic Watch
Hantaan virus vs Puumala virus
A factual side-by-side comparison of two hantavirus strains: Hantaan virus and Puumala virus. Reservoir biology, geographic distribution, clinical course, case-fatality rate, and outbreak history.
Discovery and history
Hantaan virus
Between 1951 and 1954, roughly 3,000 United Nations soldiers near the Hantaan River in central Korea developed an unexplained hemorrhagic fever with renal involvement. The case-fatality rate approached 10 percent. The disease was given the descriptive name 'Korean hemorrhagic fever' and an etiology was sought for the next 25 years. Karl Johnson and Ho Wang Lee finally isolated the causative agent from striped field mice in 1976, naming it after the river. The discovery established hantaviruses as a coherent family and provided the type species against which all subsequent strains have been characterized.
Puumala virus
Puumala virus was isolated in 1980 from bank voles trapped near the village of Puumala in southeastern Finland — the source of the name. The recognition that a hantavirus could produce a comparatively mild renal syndrome (rather than the lethal HFRS of Hantaan virus or the lethal pulmonary syndrome of Sin Nombre virus) significantly broadened the clinical spectrum understood at the time. The Finnish vernacular name for the illness, 'myyräkuume' — vole fever — reflects how thoroughly it was integrated into Northern European medicine.
Reservoir and ecology
Hantaan virus
The reservoir is the striped field mouse (Apodemus agrarius), widely distributed across temperate East Asia in grasslands, agricultural fields, and forest margins. The species is intimately associated with grain agriculture across China, Korea, and the Russian Far East, which puts it in regular contact with farmers, harvesters, and rural residents. Seasonal peaks in HFRS cases track the autumn harvest and the spring planting cycles when human exposure to rodent-contaminated environments is highest.
Puumala virus
The bank vole (Myodes glareolus, formerly Clethrionomys glareolus) is the exclusive reservoir. The species is widely distributed across the European broadleaf and mixed-forest belt from Ireland to the Urals and is one of the most abundant small mammals in its range. Bank vole populations undergo multi-year cycles tied to mast years of beech and other forest seed-bearing trees, and Puumala virus case incidence tracks those cycles with a one-year lag. The 2007 and 2010 European Puumala virus outbreak years were classic mast-driven events.
Clinical course
Hantaan virus
HFRS classically progresses through five phases: febrile (fever, myalgia, headache, lasting 3-7 days), hypotensive (sudden drop in blood pressure, lasting hours to days), oliguric (acute kidney injury with reduced urine output, lasting 3-7 days — most deaths occur here), diuretic (recovery of urine output), and convalescent (gradual recovery over weeks to months). Hemorrhagic manifestations — petechial rash, conjunctival hemorrhage, gastrointestinal bleeding — give the syndrome its name. The case-fatality rate of 5 to 15 percent is lower than for HPS but the overall morbidity is substantial.
Puumala virus
Puumala-virus illness is milder than other HFRS forms. Patients develop fever, myalgia, headache, abdominal pain, and visual disturbances (blurred vision is a classically described early symptom). A subset progress to acute kidney injury requiring dialysis. Hemorrhagic manifestations are typically limited to mild petechiae. Case-fatality is below 1 percent. Most patients recover fully within weeks; chronic kidney effects are uncommon but documented in a minority of severe cases.
Notable outbreaks
Hantaan virus
The Korean War cases between 1951 and 1954 remain the largest documented Hantaan virus event. Modern outbreaks are smaller — clusters in agricultural workers, military trainees, or rural communities during harvest peaks. China has documented major HFRS outbreaks tied to flood-displacement of rodent populations.
Puumala virus
Puumala virus does not produce outbreaks in the cluster sense — cases are diffuse across endemic regions. What it does produce are 'epidemic years' tied to vole population peaks: 2007 across Germany and France, 2010 across Western Europe, and others. Finland sees baseline-level case counts in non-peak years and several-fold increases in peak years.
Prevention
Hantaan virus
Inactivated HFRS vaccines have been licensed in South Korea since 1990 and in China shortly thereafter. They are recommended for high-risk occupational groups (military, agricultural workers, lab researchers) and provide partial protection against Hantaan and Seoul viruses. Uptake outside occupational programs is limited. Beyond vaccination, standard rodent-exposure precautions and grain-storage rodent-proofing reduce risk.
Puumala virus
Aerosol exposure during cleanup of summer cottages and woodsheds after a vole-population winter is the dominant risk factor. Northern European public health agencies issue seasonal guidance encouraging wet-method cleanup, ventilation of closed structures, and N95 use when disturbing accumulated rodent debris. There is no licensed vaccine for Puumala virus specifically.
Full strain profiles: Hantaan virus · Puumala virus. For the broader disease guide, see hantavirus.
