Crimean-Congo hemorrhagic fever in Sistan and Baluchestan Province of Iran, a case-control study on epidemiological characteristics.

Objectives: Several cases of Crimean-Congo hemorrhagic fever (CCHF), an arboviral disease, have been reported since summer 1999 in different areas of Iran. The main objectives of this research were to determine the most important means and patterns of transmission and the epidemiologic characteristics of this disease.
Design: In this population-based case-control study, 24 patients from Zabol and Zahedan Districts in the Sistan and Baluchestan province, reported to the Center for Disease Control of Iran, were compared with 300 controls. The controls were sampled through the 'probability proportional to size cluster sampling' method from the general population of the same districts. The following variables were checked: age, sex, living environment (rural versus urban), education years, job, past history of tick bite, contact history with livestock, history of livestock slaughtering, presence of a designated place for animals at home, history of keeping livestock in the house.
Results: Variables which increased the chance of disease include: history of slaughtering (OR = 7.57, CI: 2.21-25.91), high-risk occupations (OR = 4.97, CI: 0.97-25.43), history of tick bite (OR = 105.89, CI: 9.32-1202.44), age above 40 years (OR = 7.32, CI: 1.06-50.26).
Conclusion: The results of this study confirm that the scheme of risk factors and risk groups for Crimean-Congo hemorrhagic fever (CCHF) in Iran do not differ substantially from the other parts of the world. Even though tick bite is one of the most important risk factors for CCHF, it cannot explain all cases and there are other important risk factors such as high-risk occupations and having contact with livestock. Even taking care of livestock for a short period at home can increase the chance of contracting CCHF.