43(5):576-580,2002 CLINICAL SCIENCES Dinara – New Natural Focus of Hemorrhagic Fever with Renal Syndrome in Croatia Dragan Ledina, Nikola Bradariæ, Berislav Borèiæ 1 , Branko Turkoviæ 1 , Ivo Iviæ, Jozo Bakiæ 2 , Marijan Erceg 2 , Nikola Tvrtkoviæ 3 Department for Infectious Diseases, Split University Hospital, Split; 1 Croatian Institute of Public Health, Zagreb; 2 Institute of Public Health, Split; and 3 Croatian Natural History Museum, Zagreb, Croatia Aim. To investigate the characteristics and determine risk factors for hantanvirus infection in natural focus of hemor- rhagic fever with renal syndrome (HFRS) on the Dinara Mountain, where outbreak of disease emerged among Cro- atian 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 sol- diers 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 cap- tured animals by means of direct immunofluorescence assay. The most important features of HFRS were retrospec- tively 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 sol- diers sojourning in this region of natural focus with no apparent signs of HFRS. Epidemiological questionnaire in- cluded 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 hemor- rhagic symptoms and pronounced renal insufficiency, was present in 19/37 patients. The epidemiological questi- onnarie 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 suf- fered from a mild form of HFRS, which predominates in south-eastern Europe, without lethal outcome. Key words: disease reservoirs; hantavirus; hantavirus infections; hemorrhagic fever with renal syndrome; military personnel; rodentia; risk factors; war Hemorrhagic fever with renal syndrome is an acute infectious disease caused by a virus from the Bunyaviridae family, Hantavirus genus. It is a natural focus zoonosis. The infection is spread by inhalation of aerosol formed by the excretions of mouse-like ro- dents of the Apodemus, Chletrionomys, Microtus, and Ratus genus (1). The principal clinical character- istics of hemorrhagic fever with renal syndrome are fever, hemorrhages, and renal insufficiency. Mortality is low, up to 10%, in contrast to Hantavirus pulmo- nary syndromes where it reaches 50% (2). The dis- ease is common among soldiers during training and in war (3). The limited knowledge of natural foci of hemorrhagic fever with renal syndrome in Croatia, to- gether with persistent military activities, contributed to an increased number of cases during the war in Croatia (4). In Croatia hemorrhagic fever with renal syndrome was described for the first time in 1954 in four patients (5). The first cases of hemorrhagic fever with renal syndrome in military personnel in Croatia were described among soldiers of former Yugoslav Federal Army in 1989 near Velika Gorica, with 14 diseased (6). Among soldiers of Croatian Army, seven cases of hemorrhagic fever with renal syndrome ap- peared during 1991 and 1992 (7), and 125 cases in 1995. The disease broke out in the previously known foci in west Slavonia and on the mount of Mala Kapela, and, for the first time, on the mountain of Dinara in 1995 (8). The appearance of hemorrhagic fever with renal syndrome among soldiers on the mountain Dinara in 1995 prompted us to investigate whether it was a case of a new focus. Thirtyseven out 576 www.cmj.hr