An observation on correlation between rainfall and the prevalence of clinical cases of dengue in Thailand

Background & objectives: An investigation was carried out in Thailand to study the correlation between rainfall and prevalence of dengue infection during 2002–03, which can be used for prevention and control of the disease. Methods: Rainfall data (2002–03) collected from Ministry of Public Health were utilised for transformation of the infection and the rainfall data were derived from Royal Irrigation Department, Thailand. The correlation between the rainfall and the prevalence of dengue was assessed by regression analysis. Results: The least square equation plot prevalence (y) versus rainfall (x) is y = 3.0x + 4.6 (r = 0.78, p < 0.05) (r = 0.68, p < 0.05). Interpretation & conclusion: The study indicated that the prevalence of dengue infection in Thailand may depend on rainfall. Therefore, the surveillance and control of mosquito should be intensified during the period with high rainfall is recommended. However, the other confounding factors like ambient temperature and humidity which also determine the transmission of dengue should be looked into, before concluding that the increased prevalence is a result of rainfall alone. Further, similar studies to assess the correlation between the rainfall and prevalence of infection in the other countries are required to confirm these observations. Key words Correlation – dengue – rainfall – Thailan