Background: Q fever shows a wide diversity of clinical manifestation. Qfever is endemic in northern Croatia, but the epidemiological and clinical characteristics of this diseasein various ecological areas of southern Croatia are unclear. Material/Methods: From January 1985 to December2002, acute Q fever cases hospitalized at Split University Hospital were analyzed. Acute Q fever wasdefined as fever (>38 degrees C) with clinical findings in lung and/or liver verified by serologic testingwith Coxiella burnetii phase II antigen. Results: During the period of observation, 155 acute Q fevercases were hospitalized. The mean incidence of acute Q fever in the study region was 0.20/100,000/year(95%CI:0-0.78) in the coastal area and 4.64/100,000/year (95%CI:0.44-8.85) in the non-coastal areas,with a male predominance (chi(2)=60.0; p=0.0000) and a mean male to female ratio of 4.2:1. People ofessentially all ages (4-76 years) were affected, the highest rate of infection being recorded in 20-to 49-year-old age groups. In contrast to adults, girls were more frequently affected than boys (2:1).No case of acute Q fever was recorded on any of the nearby islands. Clinically, acute Q fever most commonlypresented with both pneumonia and hepatitis (60.0%), followed by pneumonia (25.8%), hepatitis (9.0%),and nonspecific febrile illnesses (5.2%). Conclusions: C. burnetii is endemic in rural, coastal, andnon-coastal areas of southern Croatia and is associated with stock breeding. In these areas, Q feveroccurs sporadically and epidemically. Males 20-49 years of age were the prevalent cases.

Keywords: Seroepidemiologic Studies, Seasons, Risk Factors, Q Fever - pathology, Prevalence, Pneumonia, Rickettsial - microbiology, Incidence, Hospitalization, Hepatitis - microbiology, Geography, Fluorescent Antibody Technique, Indirect, Croatia - epidemiology, Coxiella burnetii - immunology, Antibodies, Bacterial - analysis, Age Distribution