News Excerpt:

Researchers have found a potential link between anomalies in sea-surface temperatures in the Indian Ocean and the intensity of dengue epidemics globally, offering hope for improved prediction of dengue outbreaks.

Methodology of the study:

• The study published in the journal Science identified a specific indicator, the Indian Ocean basin-wide (IOBW) index.
• IOBW represents the average sea-surface temperature variations across the tropical Indian Ocean. 
• In this study, the researchers used data on yearly dengue cases reported from across each of the 46 Southeast Asian and American countries from 1990-2019. 
• Data of monthly cases from 24 of these countries reported from 2014-19 was also used for analysis.
• Through modelling, the team drew associations between changes in climate patterns around the world and those in seasonal and yearly case numbers during dengue epidemics.

Key highlights of the study:

• Indian Ocean basin-wide (IOBW) index, according to the study, exhibits a close association with dengue outbreaks in both the Northern and Southern hemispheres.
• The IOBW index’s association with the Southern Hemisphere is stronger than that with the Northern Hemisphere.  
• The index has a more pronounced impact on temperatures in tropical regions. 
• Brazil, for example, bears a higher burden of dengue in the Southern Hemisphere.
• It demonstrates that the IOBW index substantially affects the local temperature worldwide, influencing dengue transmission.
• These initial findings suggested that the index could be a potential indicator to forecast the interannual and seasonal magnitude of global dengue epidemics.

Current method of forecasting dengue outbreaks:

• Precipitation and temperature are some of the climate indicators that are being used as early warning systems to forecast disease trends such as dengue.

Limitations of the study:

• The team could not fully evaluate the IOBW index as some countries did not have publicly available annual and monthly case reports.
• The study also did not consider other factors that may influence dengue transmission, such as vector control measures, social and economic factors, and local herd immunity.

Way Forward:

• Future research should focus on incorporating other potential factors and establishing a comprehensive set of indicators for a dengue early warning system,
• More data is needed to establish causality, meaning that IOBW influences local temperature changes and the resultant increase in dengue incidence in many countries.