Geographical factors and air raid alarms influence leptospirosis epidemiology in Ukraine (2018-2023)

Leptospirosis, a widespread zoonotic disease caused by Leptospira spp., affects approximately 1 million people annually and causes about 58,000 deaths worldwide. This study examines the epidemiology of leptospirosis in Ukraine from 2018 to 2023, focusing on the impact of weather and geographical factors on disease transmission. Data from the Ukrainian Centre for Disease Prevention and Control, the Ukrainian Hydrometeorological Center, and the State Agency of Water Resources of Ukraine were analyzed. The country was divided into five regions: North, East, Center, South, and West. For the visualization, but not the quantitative analyses, the notification rate (NR) of leptospirosis was classified into three categories: low, moderate, and high. The highest NR were in Zakarpattia, Ivano-Frankivsk, Khmelnytskyi, Mykolaiv, and Kherson regions, with Zakarpattia having the highest rate. We analyzed whether various weather parameters-such as average annual temperature, precipitation, days with precipitation >= 1 mm, and relative humidity-were associated with the notification rate (NR) of leptospirosis, but no significant correlations were detected. However, a significant positive correlation was observed between higher density of the river network and NR (Kendall's rank correlation, r = 0.65, p = 0.0005), indicating that geographical factors may play an important role in Leptospira transmission. Additionally, we found a significant correlation between monthly air raid alarm frequency and the NR of leptospirosis cases in 2023. Case reports of individuals contracting leptospirosis in bomb shelters further support the hypothesis that air raid evacuations impact leptospirosis epidemiology. Further investigation is needed to fully understand this relationship and its implications.