Impacts of El Niño Southern Oscillation and Indian Ocean Dipole on dengue incidence in Bangladesh.

Shahera Banu,Pat Dale,John S Mackenzie,Kerrie Mengersen,Yuming Guo,Wenbiao Hu,Shilu Tong

doi:10.1038/srep16105

Abstract

Dengue dynamics are driven by complex interactions between hosts, vectors and viruses that are influenced by environmental and climatic factors. Several studies examined the role of El Niño Southern Oscillation (ENSO) in dengue incidence. However, the role of Indian Ocean Dipole (IOD), a coupled ocean atmosphere phenomenon in the Indian Ocean, which controls the summer monsoon rainfall in the Indian region, remains unexplored. Here, we examined the effects of ENSO and IOD on dengue incidence in Bangladesh. According to the wavelet coherence analysis, there was a very weak association between ENSO, IOD and dengue incidence, but a highly significant coherence between dengue incidence and local climate variables (temperature and rainfall). However, a distributed lag nonlinear model (DLNM) revealed that the association between dengue incidence and ENSO or IOD were comparatively stronger after adjustment for local climate variables, seasonality and trend. The estimated effects were nonlinear for both ENSO and IOD with higher relative risks at higher ENSO and IOD. The weak association between ENSO, IOD and dengue incidence might be driven by the stronger effects of local climate variables such as temperature and rainfall. Further research is required to disentangle these effects.

Highlights

Dengue is a major public health problem in many countries of the tropical and subtropical regions of the world
We found that El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) might play a role in the inter-annual variation in dengue incidence in Bangladesh
The ENSO has been reported to be a driver of the inter-annual variation of endemic dengue in many parts of the world[5,18,19,20,21]

Summary

Introduction

Dengue is a major public health problem in many countries of the tropical and subtropical regions of the world. ENSO is a contributor to monsoon rainfall in the Indian region and influences world weather[6]. The large positive values of ENSO are associated with El Niño events which cause dry conditions in the Indian region[7]. La Niña events are associated with large negative values of ENSO that cause increased rainfall and wet conditions in this region. The IOD plays an important role as a modulator of the Indian summer monsoon rainfall (ISMR) and influences the correlation between the ISMR and ENSO12. A positive IOD event significantly increases the monsoon rainfall over the Indian region and reduces the effects of ENSO on ISMR12. We examined the relationship between ENSO, IOD and the incidence of dengue, using a 13-years dataset from Bangladesh where the disease is endemic[13,15]

Methods

Results

Conclusion