Before Sin Nombre — The Long Pre-1993 History of Hantavirus from the Korean War to the Hantaan River

Most popular accounts of hantavirus start with the 1993 Four Corners outbreak in the United States. But by 1993 the scientific community already knew about hantaviruses — they had just never seen this particular pulmonary picture before. The longer history reaches back to World War I, runs through the Korean War, and pivots in 1976 with a discovery on a small Korean river. This is the story of how we learned that rodent-borne haemorrhagic fevers were a single viral family.

Trench nephritis — World War I, 1915-1918

The first plausibly hantavirus-attributable outbreak in the documented medical literature is "trench nephritis," an epidemic of acute kidney injury that struck British, French and German soldiers in the western front trenches from 1915 onwards. Tens of thousands of cases were documented; presentation was a flu-like illness followed by oliguria, oedema and renal failure. The cause was unidentified at the time and the connection to hantaviruses was made retrospectively decades later.

The trenches were extensively colonised by field mice and rats — the textbook hantavirus exposure environment. Modern serological analysis of preserved WWI tissue samples has supported the hantavirus hypothesis though the exact viral species cannot now be retrospectively isolated.

Songo fever and Manchurian outbreaks — 1930s-40s

Japanese army medical reports from Manchuria in the 1930s and 1940s describe a disease they called "Songo fever" or "epidemic haemorrhagic fever" — striking soldiers with sudden fever, low blood pressure, kidney failure and bleeding. Tens of thousands of cases were recorded across Japanese occupation zones. Once again, the agent was unidentified at the time but the clinical picture and rodent-rich environment fit what we now recognise as hantavirus disease.

Korean War — 1951-1953

The Korean War made hantavirus a major military medical problem for the first time at scale visible to Western medicine. Between 1951 and 1953, more than 3,000 UN forces personnel — primarily US troops — were hospitalised with what was then called "Korean haemorrhagic fever." Case fatality ran around 5-15% despite forward hospital care.

The outbreak triggered the first sustained Western epidemiological investigation of the disease. By the mid-1950s, physicians at the US Army surgical hospitals had characterised the clinical course in detail and pinned the seasonal pattern to rodent activity, though the actual viral agent remained elusive.

The 1976 breakthrough — Ho-Wang Lee and Hantaan virus

The decisive scientific breakthrough came two decades after the Korean War, in 1976, from South Korean virologist Ho-Wang Lee and colleagues at Korea University. Lee trapped striped field mice (Apodemus agrarius) along the Hantaan River near the Korean DMZ — an area that had been an outbreak hotspot during the war — and used immunofluorescence on lung tissue from the trapped mice to identify viral antigen. The agent bound antibodies from convalescent Korean haemorrhagic fever patients. That was the link: the disease soldiers had been getting was caused by a virus carried by these specific field mice. The virus was named Hantaan virus after the river.

Lee's discovery opened the floodgates. Within a decade, related viruses had been identified across Eurasia: Seoul virus (in urban rats, identified 1980), Puumala virus (in bank voles, Finland, 1980), Dobrava virus (Balkans, 1992). The genus "Hantavirus" was formally recognised, named after the Hantaan River where the type species was found.

The Americas were a blank — until 1993

Throughout the 1980s, the assumption among most virologists was that hantaviruses were an Old World problem. North and South American medical surveillance had not turned up convincing cases; the working hypothesis was that the New World rodents simply did not carry these viruses. This assumption ended in May 1993 when the Four Corners outbreak forced the discovery of Sin Nombre virus and revealed an entirely new clinical picture — pulmonary rather than renal.

Argentina then quickly identified its own version, Andes virus, in 1995. Hantaviruses were everywhere; the world had simply not been looking carefully enough.

Why this history matters in 2026

The MV Hondius outbreak is the latest chapter of a story that runs back over a century. The pattern remains consistent: rodent-borne, geographically constrained, occasionally transmissible between humans, lethal in a minority of cases. What is new in 2026 is the cruise-ship vector and the international transport of cases — the underlying biology has not changed.

Related reading

• Four Corners 1993 — the discovery of Sin Nombre virus
• Why the Andes strain is unique among hantaviruses
• Hantavirus endemic regions worldwide
• Full hantavirus outbreak history (1993–2026)