Assessment of the Influence of Climatic Factors on the Incidence of Crimean Hemorrhagic Fever: a Comprehensive Analysis of Data for Russia, Kazakhstan, Turkey and Iran between 1999 and 2022

Abstract

In recent decades, the epidemiology of vector-borne infectious diseases has changed significantly due to global warming, which affects the habitats of vectors and increases the rate of spread of pathogens. This can lead to both the expansion of the boundaries of existing and the emergence of new natural foci of infectious diseases, including Crimean hemorrhagic fever (CHF). The aim of the study was to comprehensively assess the possible impact of climatic factors on the incidence of CHF in the endemic areas of Russia, Kazakhstan, Turkey and Iran in 1999–2022. Materials and methods. The data on the number of laboratory-confirmed cases of CHF in the endemic regions of Russia, Kazakhstan, Turkey and Iran were analyzed and compared with annual climatic indicators (average annual temperature, the highest and lowest average annual temperatures and average annual precipitation) starting from 1999. Results and discussion. During the observation period, the incidence of CHF in the regions under consideration was featured in a variety of trends. Correlation analysis revealed a positive relation between the average annual precipitation and CHF cases (rxy=0.553; p<0.001), while temperature parameters were not statistically significant. Regression analysis confirmed the importance of dummy variables representing countries and time period, but did not show statistically significant relations between climatic factors. The total (in the countries under consideration) average annual precipitation is a statistically significant factor (b=1.600; s.e.=0.192; p<0.001), which emphasizes the potential impact of changing climatic conditions on the spread of the Crimean-Congo hemorrhagic fever virus. The multiple linear regression method revealed a statistically significant effect of the highest air temperature (b=27.645; s.e.=7.859; p<0.001) and precipitation (b=1.473; s.e.=0.197; p<0.001) on the incidence of CHF. The study shows the need to include annual climate forecasting in CHF control strategies and to develop unified monitoring systems for a more accurate assessment of the epidemiological situation in endemic regions.

Keywords

• crimean-congo hemorrhagic fever virus
• incidence of crimean hemorrhagic fever
• endemic regions
• global climate warming
• the impact of climate change on morbidity rates