Comparative Assessment of Environmental Determinants and Seasonal Patterns of Major Infectious Disease Outbreaks in India

Abstract

Comparative evidence of the influence of climatic variability and transition seasons on persistence of pathogens, vector ecology, environmental contamination, and exposure of populations is scarce for numerous infectious diseases in India. This study compared the epidemiological characteristics, environmental determinants, and seasonal patterns of major infectious disease outbreaks in India and identified disease-specific associations with outbreak case counts. A retrospective observational analysis was conducted using weekly district-level outbreak records for acute diarrhoeal disease, dengue, chikungunya, cholera, and malaria. Descriptive statistics summarized outbreak burden, geographic coverage, climatic conditions, and seasonality. Kruskal–Wallis tests evaluated differences in temperature, precipitation, and Leaf Area Index across diseases, while disease-specific multivariable negative binomial regression models estimated adjusted incidence rate ratios with 95% confidence intervals. The analysis included 8,679 outbreak records representing 779,693 reported cases across 782 districts. Acute diarrhoeal disease exhibited the largest outbreak burden and widest geographic distribution. Monsoon was the predominant season for all diseases, accounting for 42.0%-61.7% of outbreaks. Significant differences in temperature, precipitation, and Leaf Area Index were observed among diseases (P<0.001). Dengue showed a strong positive association with precipitation, whereas higher Leaf Area Index was associated with lower dengue incidence. Acute diarrhoeal disease, chikungunya, and cholera demonstrated distinct seasonal and environmental relationships. The results suggest that different major disease types in India are sensitive to climate, underscoring the need for climate-informed infectious disease surveillance to enhance preparedness for outbreak response, early warning systems and targeted public health interventions.