Disease burden of Puumala virus infections, 1995-2008.

Puumala virus (PUUV) causes mild haemorrhagic fever with renal syndrome, a rodent-borne zoonosis. To evaluate the disease burden of PUUV infections in Finland, we analysed data reported by laboratories to the National Infectious Disease Registry during 1995-2008 and compared these with data from other national registries (death, 1998-2007; hospital discharge, 1996-2007; occupational diseases, 1995-2006). A total of 22,681 cases were reported (average annual incidence 31/100,000 population); 85% were in persons aged 20-64 years and 62% were males. There was an increasing trend in incidence, and the rates varied widely by season and region. We observed 13 deaths attributable to PUUV infection (case-fatality proportion 0.08%). Of all cases, 9599 (52%) were hospitalized. Only 590 cases (3%) were registered as occupational disease, of which most were related to farming and forestry. The wide seasonal and geographical variation is probably related to rodent density and human behaviour.