Trends, Seasonal Shifts, and Family Clustering of Brucellosis in the Osh Region of the Kyrgyz Republic: a Retrospective Analysis of the Epidemiological Situation for 2020–2025

Abstract

This study presents the results of a retrospective epidemiological analysis of brucellosis incidence among the population of Osh Region, Kyrgyz Republic, during 2020–2025. Based on official statistical reporting data, incidence rates (per 100,000 population), seasonal indices, and family cluster characteristics were calculated, and a territorial ranking analysis was performed. The overall incidence rate during the study period ranged from 5.3 to 9.5 per 100,000 population, reaching its highest value in 2025, which was 1.5 times higher than in 2020. The incidence among children under 14 years of age, which had decreased from 3.6 in 2020 to 2.5 in 2024, increased sharply to 5.5 in 2025, representing the highest pediatric incidence recorded during the six-year period. Monthly analysis revealed a variable seasonal pattern, with peak incidence shifting between spring, summer, and autumn in different years. In 2025, the seasonal increase extended from April to October, with four months exceeding 1.2 cases per 100,000 population. The September incidence rate (1.34 per 100,000) was the highest monthly value recorded during the entire study period. Seasonal indices confirmed the greatest activity in June (158%) and September (137%). Analysis of family clusters (13 clusters involving 34 cases, with an average of 2.6 cases per cluster) demonstrated their uneven geographical distribution. The highest concentration of cases was observed in Alay District (35.3% of all cluster-associated cases) and Nookat District (20.6%), whereas no family clusters were registered in Aravan and Kara-Kulja districts. The findings indicate a substantial deterioration of the epidemiological situation of brucellosis in Osh Region in 2025, particularly among children, accompanied by pronounced but unstable seasonality and a significant contribution of family clusters to disease transmission. The results substantiate the need to strengthen veterinary surveillance, implement a differentiated approach to planning anti-epidemic measures with consideration of seasonal shifts, and conduct targeted health education activities in areas characterized by a high level of family clustering.