Role of seasonality and rainfall in Vibrio cholerae infections: A time series model for 11 years surveillance data

BackgroundCholera is a life threatening disease, which alone contributes to the mortality of 2.2 million people globally, per year. The aim of this article was to study the trend, seasonality and the association of Vibrio cholerae(V. cholerae) cases with environmental factors such as Rainfall, Temperature and Humidity over 11 years.MethodsData on V. cholerae were extracted from laboratory records of Department of Clinical Microbiology, Christian Medical College, Vellore (India) between 2000 and 2010. Time series models such as Auto regressive model, Seasonal auto regressive integrated moving average model, Segmented regression model and Harmonic regression model with sine and cosine functions were done to analyze the data.ResultsThere were 132 months of observations and 1039 cholera cases reported during this time. The total number of Vibrio cholerae O1 and O139 reported was 940 and 99 cases, respectively. The number of cases reported gradually declined after 2004. The overall mean (sd) of monthly cholera counts was 7.9 (8.2). Results suggested that there was a near significant reduction of 50% from 2000–2004 to 2005–2010 with mean (sd) were 11.2(8.0) and 5.1(7.4) respectively. The average peak time during the first time period was August, while July was during the second time period. During 2000–2004, there was a positive significant association between Rainfall and V. cholerae cases (r = 0.51, p < 0.001) and this was not observed in the second time period.ConclusionThe trend of V.cholerae was decreasing from 2000 to 2010 and there was a significant association between Rainfall and cholera cases between 2000 and 2004.