Dengue Patterns in Kerala Linked to Climate and Projected Shifts

Scientific research indicates that climate factors play a substantial role in dengue patterns in Kerala, with projections suggesting changes in incidence rates due to ongoing climate shifts.

Kerala has experienced multiple dengue epidemics over the past two decades, with major outbreaks recorded in 2003, 2010, 2012, 2013, 2016, and 2017. The highest annual case count was reported in 2017, when nearly 20,000 cases were documented.

Studies have found that rainfall and relative humidity in Kerala are directly linked to increases in dengue cases, with these weather conditions showing immediate effects. Other environmental factors, such as soil moisture, the Nino3.4 index, and average temperature, have been shown to influence dengue cases with time lags of one to three months.

Across Asia, research has identified a broad connection between climate change and the spread of dengue. Historical temperature increases have been associated with an estimated 18% rise in dengue incidence, and future warming is projected to further raise incidence rates by up to 76% by the middle of the century, depending on emission scenarios.

What the numbers show

• Kerala recorded 19,994 dengue cases in 2017, the highest annual total to date.
• Historical warming has increased dengue incidence in Asia by about 18% on average.
• Future warming could raise dengue incidence by 49% to 76% by mid-century under various emission scenarios.
• Projections for Pune indicate dengue mortality could rise by 12-13% by 2040 and up to 112% by 2100 under high emissions.
• Kerala and Goa may see a relative decrease in dengue incidence by 2030, while other southern states could see increases of 10% to 80%.

Projections for specific regions in India show differing trends. Kerala and Goa are expected to experience a relative decline in dengue incidence by 2030 under several socio-economic scenarios, while other southern states could see increases ranging from 10% to 80%.

In contrast, projections for Pune suggest a substantial rise in dengue mortality rates under high-emission scenarios, with increases estimated at 12-13% by 2040, 25-40% by 2060, and potentially reaching 112% by the end of the century.

The Kerala State Climate Change Cell has stated that climate change is increasing the risk of vector-borne diseases, including dengue, particularly in coastal areas. This assessment is included in the state's official action plan on climate change.

Lagged associations between environmental factors and dengue cases highlight the complexity of predicting outbreaks. While rainfall and humidity have immediate effects, other variables such as soil moisture and temperature influence dengue transmission with delays of up to three months.

* This article is based on publicly available information at the time of writing.