Natural foci of some viral zoonoses in Croatia

Results of several-year investigations into the epidemiology and virology of viral zoonoses with natural foci occurring in Croatia, with special reference to tick-borne encephalitis (TBE) and hemorrhagic fever with renal syndrome (HFRS), are presented. The etiologic diagnosis of these diseases was made on the basis of virus isolation from patient blood and/or findings of specific antibodies in the serum. Several TBE and Bhanja virus strains were isolated from different species of ticks, and Calovo virus from mosquitoes, while the presence of Hantaan virus antigen was determined in the lungs of certain micromammalian species, the virus natural reservoirs, by direct immunofluorescence. For the largest HFRS outbreak in Croatia to date, which occurred in 1995 during the war, a detailed description is provided. The role of the geographic aspect is indicated, because an air corridor used by migratory birds which temporarily alight in some areas for a brief stop, whereby they may introduce viruses from other parts of the world, passes just above the territory of Croatia.