Epidemiology and Infection

Epidemiology of Sindbis virus infections in Finland 1981–96: possible factors explaining a peculiar disease pattern

M.  BRUMMER-KORVENKONTIO  a1 a2 , O.  VAPALAHTI  a1 a5 c1 , P.  KUUSISTO  a3 , P.  SAIKKU  a4 , T.  MANNI  a1 , P.  KOSKELA  a4 , T.  NYGREN  a6 , H.  BRUMMER-KORVENKONTIO  a7 and A.  VAHERI  a1 a5
a1 Haartman Institute, Department of Virology, University of Helsinki, Helsinki, Finland
a2 Tvärminne Zoological Station, University of Helsinki, Hanko, Finland
a3 Ilomantsi Health Care Centre, Ilomantsi, Finland
a4 National Public Health Institute, Oulu, Finland
a5 HUCH Laboratory Diagnostics, Helsinki, Finland
a6 Finnish Game and Fisheries Research Institute, Game Research Station, Ilomantsi, Finland
a7 National Public Health Institute, Helsinki, Finland


Pogosta disease (PD), an epidemic rash-arthritis occurring in late summer is caused by Sindbis virus (SINV) and is transmitted to humans by mosquitoes. Altogether 2183 PD cases were serologically confirmed 1981–96 in Finland, with an annual incidence of 2.7/100000 (18 in the most endemic area of Northern Karelia). The annual average was 136 (varying from 1 to 1282) with epidemics occurring in August–September with a 7-year interval. Studies on 6320 patients with suspected rubella (1973–89) revealed 107 PD cases. The depth of snow cover and the temperature in May–July seemed to predict the number of cases. The morbidity was highest in 45- to 65-year-old females and lowest in children. Subclinical SINV infections were 17 times more common than the clinical ones. The SINV-antibody prevalence in fertile-age females was 0.6% in 1992; the estimated seroprevalence in Finland is about 2%. Among game animals the tetraonids (black grouse and capercaillie) had the highest seroprevalence (65%) in the epidemic year of 1981.

(Accepted April 28 2002)

c1 Author for correspondence: Haartman Institute, P.O. Box 21 (Haartmaninkatu 3), FIN-00014 University of Helsinki, Finland.