Impact of Climate Variables on Crimean-Congo Hemorrhagic Fever in Iran, Iraq, Kazakhstan, and Russia (2000–2022)

Background: Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease endemic to in Africa, Asia, and Europe. This study examined the association between climate variables and CCHF in Iran, Iraq, Kazakhstan, and Russia from 2000 to 2022. Methods: CCHF case counts were collected from published, unpublished, and surveillance data sources. Cross-correlation analysis was used to evaluate the temporal effects of rainfall and temperature on CCHF incidence, applying generalized additive mixed models (GAMMs). The Akaike information criterion (AIC) was used to determine the most appropriate model. Kendall's W examined case peaks across countries and identified significant synchronicity among CCHF cases, temperature, and rainfall across countries (p< 0.05). Results: Synchronization analysis using GAMMs identified an optimal model describing the relationship between CCHF cases and annual rainfall and temperature, with temporal lags of five and the same year, respectively. Conclusions: Lower temperatures and increased rainfall were linked to a rise in CCHF cases, indicating that these climatic factors significantly influence tick population growth and activity. Additional environmental and ecological variables should be considered in future studies to develop a more comprehensive model.