Abstract
BackgroundDengue is rapidly expanding climate-sensitive mosquito-borne disease worldwide. Outbreaks of dengue occur in various parts of India as well but there is no tool to provide early warning. The current study was, therefore, undertaken to find out the link between El Niño, precipitation, and dengue cases, which could help in early preparedness for control of dengue.MethodsData on Oceanic Niño Index (ONI) was extracted from CPC-IRI (USA) while the data on monthly rainfall was procured from India Meteorological Department. Data on annual dengue cases was taken from the website of National Vector Borne Disease Control Programme (NVBDCP). Correlation analysis was used to analyse the relationship between seasonal positive ONI, rainfall index and dengue case index based on past 20 years’ state-level data. The dengue case index representing ‘relative deviation from mean’ was correlated to the 3 months average ONI. The computed r values of dengue case index and positive ONI were further interpreted using generated spatial correlation map. The short-term prediction of dengue probability map has been prepared based on phase-wise (El Niño, La Niña, and Neutral) 20 years averaged ONI.ResultsA high correlation between positive ONI and dengue incidence was found, particularly in the states of Arunachal Pradesh, Chhattisgarh, Haryana, Uttarakhand, Andaman and Nicobar Islands, Delhi, Daman and Diu. The states like Assam, Himachal Pradesh, Meghalaya, Manipur, Mizoram, Jammu & Kashmir, Uttar Pradesh, Orissa, and Andhra Pradesh shown negative correlation between summer El Niño and dengue incidence. Two - three month lag was found between monthly ‘rainfall index’ and dengue cases at local-scale analysis.ConclusionThe generated map signifies the spatial correlation between positive ONI and dengue case index, indicating positive correlation in the central part, while negative correlation in some coastal, northern, and north-eastern part of India. The findings offer a tool for early preparedness for undertaking intervention measures against dengue by the national programme at state level. For further improvement of results, study at micro-scale district level for finding month-wise association with Indian Ocean Dipole and local weather variables is desired for better explanation of dengue outbreaks in the states with ‘no association’.
Highlights
Dengue is rapidly expanding climate-sensitive mosquito-borne disease worldwide
A number of studies undertaken in South Asia [14, 16, 18, 25] and Oceania, South America, and in Central America [15, 26, 27] revealed the possibility of early warning of dengue outbreaks based on El Niño Southern Oscillation (ENSO) phases
The current research has shown that the dengue outbreaks are highly correlated with ENSO, monsoon and post-monsoon rainfall in the states like
Summary
Dengue is rapidly expanding climate-sensitive mosquito-borne disease worldwide. Outbreaks of dengue occur in various parts of India as well but there is no tool to provide early warning. Dengue is an emerging vector borne disease due to rapid urbanization, scarcity of water and changing climatic conditions all over the globe. Owing to interannual variability in climatic conditions, the sudden occurrence of dengue (outbreaks) is generally witnessed in many subtropical and tropical countries of the world [2, 3]. As per World Health Organization [4], dengue is a rapidly growing mosquito-borne arbo-viral disease in the world which has increased 30-fold in the last 50 years. An estimated 390-million dengue infections occur annually [5], and 2.5 billion population live in dengue-endemic countries [6] posing a serious public health challenge [7]
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