Climate influences scrub typhus occurrence in Vellore, Tamil Nadu, India: Analysis of a 15-year dataset

Abstract

Abstract Background Climate is one of the major factors determining the prevalence and seasonality of vector borne diseases like scrub typhus (ST). We analyzed, the association of the meteorological factors like temperature, rainfall and humidity with scrub typhus using the 15 years scrub typhus data from a tertiary care hospital in Vellore, South India. Methods Demographic data of permanent residents of Vellore, who had IgM ELISA results for scrub typhus for the time period of May 2005 to April 2020 were included. Meteorological data was correlated with the monthly scrub typhus cases; negative binomial regression model was used to predict the relation between scrub typhus occurrence and climate factors. Results Maximum number of ST cases were reported between the months August and February with October recording the highest number of cases. Elderly people, farmers, agricultural workers and housewives were associated with ST positivity significantly. For an increase of 1°C in mean temperature, the monthly ST cases reduced by 18.78% (95% CI: -24.12, -13.15%). On the contrary, for 1 percent increase in mean relative humidity (RH), there is an increase of 7.57% (95% CI: 5.44, 9.86%) of monthly ST cases. Similarly, an increase of 1mm of rainfall contributed to 0.50 to 0.70% of monthly ST cases (after two months) depending on the variables included in the analysis. Conclusion This study provides further information on the role of rainfall, temperature and humidity on the seasonality of scrub typhus in Vellore, South India. This baseline data will be useful for further analysis using spatio-temporal tools to better understand the seasonality in other parts of India.