Aim: To investigate the characteristics and determine risk factors for hantanvirus infection in natural focus of hemorrhagic fever with renal syndrome (HFRS) on the Dinara Mountain, where outbreak of disease emerged among Croatian soldiers in 1995, and to describe the features of HFRS acquired on the Dinara mountain and determine the scale of the largest HFRS epidemic so far in Croatia.
Methods: During 1996, small mammals were captured in the region of Dinara Mountain where infected Croatian soldiers had sojourned. By taxonomic classification of 42 captured small mammals, three species were determined: 23 yellow-necked mouse, 9 wood mouse, and 5 bank vole. Hantavirus antigen was determined in the lungs of the captured animals by means of direct immunofluorescence assay. The most important features of HFRS were retrospectively determined in 37 soldiers with HFRS treated in the Department for Infectious Diseases of the Split University Hospital. The degree of inapparent exposure to infection was determined by indirect immunofluorescence in 103 soldiers sojourning in this region of natural focus with no apparent signs of HFRS. Epidemiological questionnaire included 50 soldiers with negative serum antibodies, as well as 33 available out of total 37 soldiers with HFRS. Chi-square test was used to determine risk factors.
Results: Hantavirus was found in the lungs of 5/42 (12%) captured animals. Mild form of the disease, with few hemorrhagic symptoms and pronounced renal insufficiency, was present in 19/37 patients. The epidemiological questionnaire determined the following risk factors for hantanvirus infection in this focus: service in artillery corps (p=0.040), sleep in wooden barracks (p=0.004), station in forest biotope (p=0.037), usage of natural camouflage (p=0.024), smoking (p=0.010), and the presence of rodents in the place of housing (p<0.001).
Conclusion: A new natural focus of HFRS in Croatia, and the first one in Dalmatia, was defined by seroepidemiologic, mamologic, and virologic analysis. The risk factors for infection in the new focus have been identified. Our patients suffered from a mild form of HFRS, which predominates in south-eastern Europe, without lethal outcome.