Epidemiological study of nephropathia epidemica in Finland 1989-96

This study presents data on 33,000 serum samples studied from July 1989 to June 1996 in Finland, with 6,701 serologically confirmed Puumala virus (PUU ) infections. In addition, a PUU serosurvey of 8,000 sera from Finland is p resented. On average, 957 PUU infections were detected annually. resulting in an incidence of 19/100,000; mortality was less than 0.1%. The infection mas most common in the district or Ita-Savo with an incidence of 90/100,000 . The seasonal peak was in November-December; however, the urban population had its incidence peak in August. Local epidemics mirrored bank vole densi ties, with 3-4-y cycles. Males contracted the disease at a mean age of 40 y , females at 44 y (male:female ratio 2:1). The disease was relatively rare in children and elderly people. The nationwide PUU antibody prevalence for women entering Finnish maternity clinics was 3%, suggesting 5% for the tota l population. The highest prevalences (7% for young women) were encountered in eastern Finland. In the district with the highest clinical alert, appro ximately 30% of all PUU infections a ere estimated to lead to clinical dise ase with serological confirmation.