Crimean-Congo Hemorrhagic Fever in the Zhambyl Region: Epidemiological Features of the Occurrence of Infection in 2023

Crimean-Congo hemorrhagic fever (CCHF) is an acute tick-borne viral infection with a high fatality rate. The main vector of the CCHF virus is ticks of the genus Hyalomma. Humans get infected through tick bites or by direct contact with the blood of infected humans or domestic animals. The endemic regions of CCHF in Kazakhstan are Kyzylorda, Turkestan, and Zhambyl. In the Zhambyl region, the first evidence of human cases was reported in 1982. In the following years, cases of CCHF were annually registered in two districts (Sarysu and Moiynkum) of the Zhambyl region. The study goal is twofold: 1) to provide a retrospective review of CCHF cases reported through the surveillance system in the Zhambyl region from 1991 to 2023 and 2) to analyze epidemiological features of CCHF cases in the Zhambyl region in 2023. Surveillance data on CCHF during the 1991–2023 period in the Zhambyl region were extracted from the “Report on selected infectious and parasitic diseases”. Incidence (per 100,000 population) was defined as the number of annual new cases divided by the total population each year. Descriptive analysis was performed on case characteristics, time, and place of CCHF cases in the Zhambyl region in 2023. In total, 216 cases of CCHF were reported from 1991 to 2023. The incidence increased sharply with peak activity in 1995 and has declined since 2002. The natural foci of the disease have shifted from the Sarysu and Moiynkum districts to the Shu, Bayzak, and Zhambyl districts. Overall, 12 cases of CCHF were reported in the Zhambyl region in 2023, mainly in nonendemic (Shu, Bayzak, Zhambyl) districts. An analysis of epidemiological data for 2023 showed that the first peak of CCHF incidence was in March-June, with another peak from October to November. We observed dynamic distribution of CCHF in the Zhambyl region from 1991 to 2023, wherein Sarysu and Moiynkum endemic districts foci tended to increase by expanding to the Shu, Bayzak, Zhambyl districts. The disease trend is seasonal, and the life cycle of ticks can indirectly influence morbidity rates. Additional research is needed to elucidate the environmental, meteorological, and social factors associated with CCHF incidence in different decades.