Dr. Ho Wang Lee and collaborators, working in Seoul, Korea, were the first to isolate the virus that causes Korean hemorrhagic fever. They named it “Hantaan virus” in recognition of the Hantaan River, which transsects the endemic region of Korea near the demilitarized zone. The virus was isolated from lung tissues of the striped field mouse, Apodemus agrarius, and this species is now recognized as the major rodent host of the virus 3 .
Within a year or two of its initial isolation, Hantaan virus was adapted to grow in cell culture, which allowed for development of a serologic test 4 . The availability of both the virus and a serologic test allowed experimental infection of natural rodent hosts to be undertaken, and through these studies, one of the key characteristics of the hantaviruses was discovered. A brief viremia follows experimental inoculation of seronegative Apodemus agrarius. Subsequently, hantaviral antigen is detectable for weeks to months in many major organs, but, most importantly, infectious virus is shed in saliva, feces, and especially urine, perhaps for the duration of the rodent's life. This virus shedding occurs in spite of the presence of both indirect immunofluorescent antibody (IFA) and neutralizing antibody in serum 5 . Thus, the infected rodent becomes a persistent source of infectious virus, and we suspect that it is through aerosolized virus that is excreted in infected rodent urine and feces that most human infections occur. This persistent shedding of infectious virus by chronically infected rodents appears to be a general characteristic of all the hantaviruses and their rodent hosts, and is a critical aspect in the epidemiology of this group of viruses 6 .
Acute hantaviral infections cause a wide spectrum of illness, which typically includes abrupt onset, fever, renal dysfunction, and often hemorrhagic manifestations 7 . The name hemorrhagic fever with renal syndrome has been proposed by the World Health Organization to cover all human disease due to hantaviral infections 8 . In Asia and some parts of Europe where inadequate treatment facilities exist, mortality rates may exceed 10%, and, even with modern treatment, mortality rates of 5% or greater are not uncommon for some forms of HFRS.
A very interesting set of sera was collected by the Hemorrhagic Fever Commission during the Korean Conflict. This commission was formed by the Army to investigate the “new” hemorrhagic fever that was seen among the forces in Korea. While they were ultimately unable to isolate the causative agent, they did develop a considerable body of knowledge about both the clinical disease and its treatment. They also systematically collected acute and convalescent sera from patients studied. This collection remains intact, and we recently tested these sera for evidence of past hantaviral infection 9 .