Clinical and Laboratory Manifestations of Sindbis Virus Infection: Prospective Study, Finland, 2002–2003

Sindbis virus (SINV) is widespread in Europe, Africa, Australia, and Asia, but clinical infection occurs as epidemics in a few geographically restricted areas. We recently proved, by virus isolation from patients, that SINV is the causative agent of Pogosta disease, a mosquito-borne rash-arthritis occurring as larger epidemics every seventh year in Finland. Altogether, 86 patients with serologically verified SINV infection were recruited to the present study during the 2002 outbreak. We now describe in detail the duration, incidence, and characteristics of different symptoms; hematological parameters; antibody kinetics; and presence of SINV in different tissue samples. SINV RNA detection or virus isolation from blood and/or skin lesions was successful in 8 patients. Immunoglobulin (Ig) M antibodies became detectable within the first 8 days of illness, and IgG antibodies became detectable within the first 11 days of illness. During the acute phase of Pogosta disease, the typical symptoms were arthritis, itching rash, fatigue, mild fever, headache, and muscle pain. The most notable finding was that, in 50% of the patients, joint symptoms lasted for >12 months.