Emerging spatio-temporal trends of dengue incidence in Colombo and Kandy Districts, Sri Lanka

Abstract

BACKGROUND: Dengue has become a prominent challenge to the health sector in Sri Lanka. Prior identification/prediction of possible risk areas with high susceptibility to dengue, could be of major importance in ensuring the effective regulation of dengue epidemics. Therefore, the current study attempts to investigate the spatio-temporal trends in dengue incidence and priority risk factors that characterize dengue epidemics, aiming to stratify the Colombo and Kandy Districts into high, moderate and low risk areas via development of dengue risk maps by devising a statistical and geo-informatics based approach. METHODOLOGY: Socio-economic data of dengue patients and healthy volunteers in selected high risk MOH areas of Colombo (5) and Kandy (5) Districts were obtained through an interviewer administrated questionnaire. Previously reported dengue cases from 2009 to 2014 in each MOH were acquired. The spatio-temporal trends in dengue incidence of studied MOHs, were investigated at the Grama Niladhari Division (GND) level by using Arc GIS (version 10.2). The impacts of gender and age of the community on the disease prevalence were investigated by using normal Chi square test and Paired-Chi square test in SPSS (version 23). RESULTS: At present, 95% and 81% of the overall socio-economic surveillance has been completed in Kandy and Colombo Districts, respectively. Spatial maps on disease outbreaks have been developed for Akurana, Doluwa, Gampola, Gangawatakorale, Kandy Municipal Council (KMC), Kundasale and Poojapitiya MOH areas. According to results of the Paired-Chi square test, the emergence of dengue outbreaks indicated a significantly declining trend in recorded dengue cases in most of the GNDs within the studied MOHs, during the recent years. The Percentage Infected Male:Female Ratio (PIMFR) remained significantly altered throughout the period of study (p=0.001<0.05 at 95% of significance). Within the studied MOHs, males tend to indicate relatively high susceptibility for dengue infection than females (with 58.6: 41.5 of average PIMFR). The age group of 11 – 20 and 21 – 30 years were identified as with highest vulnerability to dengue, while the age > 61 years indicated the least vulnerability in all the MOHs. According to the Paired-Chi square test, the vulnerability of age groups was found to shift significantly throughout the study period [>Χ2 (7, 0.95) = 14.067]. CONCLUSIONS: The KMC and Gampola MOHs indicate relatively high susceptibility to dengue within the district of Kandy. Within all the studied MOHs, males tend to indicate relatively high susceptibility to dengue. Age groups of 11 - 20 and 21 – 30 denote relatively higher vulnerability to dengue, while age group of > 61 emerge as the least vulnerable group for the infection of dengue in the studied MOHs.