Seoul virus is a member of the genus Orthohantavirus (family Hantaviridae) and is an Old World hantavirus causing a mild to moderate form of hemorrhagic fever with renal syndrome (HFRS). It has a tri‑segmented negative‑sense RNA genome totalling about 12 kilobases and shares genetic features with Hantaan virus and Dobrava‑Belgrade virus. The virus was first isolated from Norway rats in the 1980s, and its name reflects its association with domestic rats that live alongside humans in cities.
Biology and Transmission
Seoul virus possesses three genome segments—small (S), medium (M) and large (L)—encoding the nucleocapsid protein, the envelope glycoproteins Gn and Gc, and the RNA‑dependent RNA polymerase. Virions are enveloped and carry a helical nucleocapsid. Within the Murinae‑associated clade of hantaviruses, Seoul virus is maintained in synanthropic rats, primarily the Norway rat (Rattus norvegicus) and the black rat (R. rattus), which are found on every continent except Antarctica. Humans become infected by inhaling aerosols of contaminated rodent urine, faeces or saliva or by direct contact with rodent excreta. Vertical transmission among rats and persistent infection in the kidneys help maintain viral circulation. Human infection can cause HFRS with fever, thrombocytopenia, proteinuria and, occasionally, acute kidney injury. Mortality is generally below 1 %, and severe cases are uncommon compared with those caused by Hantaan virus. There is no evidence of person‑to‑person transmission.
Epidemiology and Outbreaks
Seoul virus infections are closely tied to the global distribution of commensal rats. The virus was first recognized as a cause of human disease during investigations of Korean War veterans with hemorrhagic fever. Subsequent serosurveys and case reports have documented infections across Asia, Europe and the Americas. Laboratory workers handling rats have acquired infection, and sporadic cases continue to occur among residents of urban areas with high rat densities. In 2017, clusters of HFRS were linked to domestic rat breeders in the United States and Canada, prompting culling of breeding colonies. Imported rats have also introduced the virus into pet populations in Europe. Infection is typically mild and responds to supportive care; ribavirin has been used experimentally but is not licensed specifically for this virus. Control efforts focus on reducing rodent infestations and educating pet owners and laboratory staff about hygiene. No dedicated vaccine exists, though the Hantaan virus vaccine used in some Asian countries may provide cross‑protection.
Seoul virus remains an important zoonotic pathogen because of its wide host range and its ability to cause human disease in urban and peri‑urban environments worldwide. Although illness is generally less severe than that caused by other hantaviruses, awareness and rodent control are essential to prevent human exposure. Monitoring pet and wild rat populations helps detect outbreaks and mitigate spread.
Related Terms: Hantaan virus, Puumala virus, Dobrava-Belgrade virus, Sin Nombre virus, Andes virus