Seoul virus

Discovery and history

Seoul virus was isolated in 1980 from Norway rats trapped in the city for which it is named. The discovery completed an early picture of the hantavirus genus by adding an explicitly urban species to the previously wild-rodent-defined family. The recognition that an HFRS-causing virus could be carried by the cosmopolitan Norway rat — the same species that spread the bubonic plague historically and persists today in essentially every human-inhabited port — fundamentally changed how the geographic risk of hantaviruses was understood.

Rodent reservoir

The Norway rat (Rattus norvegicus) is the primary reservoir, with the black rat (Rattus rattus) also documented as a carrier in some studies. Both species are cosmopolitan in distribution, following humans through trade, transportation, and habitation. Pet rat colonies — sometimes derived ultimately from wild-caught founders — can carry and transmit Seoul virus, and several documented human outbreaks have been traced to pet rat ownership rather than wild rat exposure.

Geographic distribution

Seoul virus has been documented essentially worldwide. Confirmed circulation has been reported in Asia (Korea, China, Japan, where it is the most common HFRS-causing strain in urban populations), Europe (the United Kingdom, where multiple pet-rat-associated clusters have been documented), North America (the United States, with cases in multiple states), and elsewhere. Surveillance is uneven; presumed Seoul-virus activity wherever Norway rats live exceeds the documented surveillance footprint.

Clinical features

Seoul-virus HFRS is milder than Hantaan-virus or Dobrava-virus disease. Patients develop the classic febrile prodrome — fever, myalgia, headache, abdominal pain — and a subset progress to a renal phase with proteinuria, mild renal impairment, and occasionally hemorrhagic manifestations. Severe disease requiring dialysis occurs but is uncommon. Case-fatality is 1 to 2 percent, the lowest among the HFRS-causing strains except for Puumala virus.

Notable outbreaks

Several U.S. multi-state pet rat outbreaks have been investigated since 2017, involving home-breeder networks and rat fancier communities. United Kingdom investigations have linked pet rat ownership to sporadic Seoul virus cases as well. Wild-rat-associated cases occur in port cities globally but are typically sporadic rather than clustered.

Prevention

Prevention focuses on rodent control in urban and peri-urban environments — sealing entry points, removing food sources, and integrated pest management. Pet rat owners should follow biosecurity practices (sourcing from reputable breeders with known disease status, hygiene during cage cleaning, avoiding contact with bedding aerosols). Healthcare workers caring for pet rat owners should be aware of Seoul virus as a differential diagnosis for unexplained febrile renal illness.

Where Seoul virus circulates

Documented in the following countries. Click through for country-specific context, active outbreak status, and historical cases.

Related strains

• HTNV The prototype hantavirus, agent of severe HFRS across East Asia and the original 'Korean hemorrhagic fever' described during the Korean War.
• PUUV The mildest major hantavirus and the highest-volume one in Europe. Causes 'nephropathia epidemica' in Northern and Central Europe with a case-fatality rate below 1 percent.

Synthesized from the World Health Organization Hantavirus Fact Sheet, the U.S. Centers for Disease Control and Prevention Hantavirus Disease pages, the European Centre for Disease Prevention and Control surveillance atlas, and primary epidemiological literature. Not a substitute for individual medical advice. If you have been exposed to rodents and develop symptoms, contact a healthcare professional.

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