Haemorrhagic fever with renal syndrome: evaluation of ELISA for detection of Puumala-virus-specific IgG and IgM

IgM and IgG ELISA to Puumala virus were evaluated using sera from patients with haemorrhagic fever with renal syndrome (HFRS) from different geographical regions: Sweden, Denmark, Norway, Belgium and the European USSR. IgM ELISA proved useful in the diagnosis of HFRS in patients from all the regions mentioned above. Specific IgM could be detected as early as day 1 post onset of disease, and patients remained IgM-positive for several months. Specific IgG ELISA antibodies were also frequently detected in acute sera, and acute-convalescent serum pairs often failed to show a significant titre rise or increase in optical density (OD) values. This limits the use of IgG ELISA in patient diagnosis. Sera collected 2 years after infection revealed higher IgG ELISA OD readings than convalescent sera, and very high values were still detectable 10 to 20 years postinfection. IgG ELISA is therefore useful for the testing of immunity and in seroepidemiological studies. Acute and convalescent sera from HFRS patients in Korea and the Asian USSR showed no or only very weak reactivity in the Puumala virus IgG and IgM ELISA. These results are consistent with the "one-way" crossing described earlier.