18% dengue cases in Asia, Americas during 1995-2014 linked to climate change: Study

A new analysis of dengue cases across 21 countries in Asia and the Americas reveals that 18 per cent of disease incidence during 1995-2014 can be traced to higher temperatures resulting from climate change.

The 18 per cent translates into more than 4.6 million extra infections per year on average, researchers from Stanford and Harvard universities in the US said.

Under continued global warming, the cases of the mosquito-borne infectious disease could climb another 50-76 per cent by 2050, depending on how trends in greenhouse gas emissions play out, findings published in the journal ‘Proceedings of the National Academy of Sciences’ suggest.

Over 1.4 million cases of dengue across countries in Central and South America and Southeast and South Asia were analysed.

The team added that the estimates are likely conservative as the study excludes large regions where the disease is endemic — such as India and Africa — and where detailed data is lacking or not publicly available.

Evidence emerging from studies shows that conditions driven by climate change — rising temperatures and rainfall — are increasing the spread of dengue fever, including in regions with a history of low incidence.

However, "what is unique about this work is that we are able to separate warming from all the other factors that influence dengue — mobility, land use change, population dynamics — to estimate its effect on the real-world dengue burden," senior author Erin Mordecai, a professor of biology at Stanford University's school of humanities and sciences, said.

"This is not just hypothetical future change but a large amount of human suffering that has already happened because of warming-driven dengue transmission," Mordecai said.

The strongest effects in disease spread due to warming would occur in cooler regions, with incidence peaking near 28 degrees Celsius, the researchers projected.

Rates of dengue cases could be more than double in many cooler locations, including areas that are already home to over 260 million people, according to the study.

"We estimate that 18 per cent of dengue incidence on average in the study countries is attributable to historical climate change and further projects that future warming will lead to 49 to 76 per cent increases depending on the emissions scenario," the authors wrote.

The findings could help guide public health measures and strengthen efforts in holding governments and fossil fuel companies to account for damage caused by climate change, the researchers said.

Attribution studies — which help ascertain how much climate change contributed towards an event, such as extreme rainfall, heatwave or disease spread — including this analysis are increasingly entering courtrooms and policy debates for accountability and to support a transfer of funds to affected countries as compensation, the team said.

They added that an aggressive mitigation of climate change and improved adaptation — involving a better control of mosquitoes, resilient health systems and a widespread use of new vaccines -- are required.