By AFP - Agence France Presse
Fifth of dengue cases are due to climate change: researchers
Daniel Lawler
Climate change is responsible for nearly a fifth of the record number of dengue fever cases worldwide this year, US researchers said on Saturday, seeking to shed light on how rising temperatures help spread the disease.
Researchers have been working to rapidly demonstrate how man-made climate change directly contributes to individual extreme weather events such as hurricanes, wildfires, droughts, and floods that have ravaged the world this year.
But relating how global warming affects health - such as driving outbreaks or spreading diseases - remains a new field.
“Dengue is a good first disease to focus on because it is very sensitive to climate,” Erin Mordecai, an infectious disease ecologist at Stanford University, told AFP.
The viral disease, which is transmitted by the bite of infected mosquitoes, causes fever and body aches and can, in some cases, be deadly.
It is generally confined to tropical and subtropical areas, but rising temperatures have caused mosquitoes to invade new areas, taking dengue with them.
For the new study, which has yet to be peer-reviewed, a team of US researchers analyzed how higher temperatures were linked to dengue infections in 21 countries in Asia and the Americas.
On average, around 19% of current dengue cases worldwide are “attributable to climate warming that has already occurred,” said Mordecai, the senior author of the pre-print study.
Temperatures between 20-29 degrees Celsius (68-84 degrees Fahrenheit) are ideal for the spread of dengue, said Mordecai.
The elevated areas of Peru, Mexico, Bolivia, and Brazil, which will warm up in this temperature range, could see an increase of up to 200% in dengue cases over the next 25 years, according to the researchers.
The analysis estimated that at least 257 million people currently live in areas where global warming could double the rate of dengue during this period.
This danger is just “another reason why you should be concerned about climate change,” said Mordecai.
- Bacteria to the rescue? -
More than 12.7 million cases of dengue fever have been recorded worldwide this year up to September, almost double the 2023 record total, according to data from the World Health Organization.
But Mordecai said that a “huge amount of under-reporting” meant that the real figure was likely to be closer to 100 million.
The research was presented at the annual meeting of the American Society of Tropical Medicine and Hygiene in New Orleans.
Another body of research, also not peer-reviewed, has raised hopes of a possible tool to help combat the rise in dengue fever.
It involves breeding mosquitoes infected with a common bacterium called Wolbachia, which can block the insect's ability to transmit dengue.
Five years ago, mosquitoes infected with Wolbachia were introduced to most of the Brazilian city of Niterói.
When Brazil faced its worst-ever dengue outbreak this year, there was only a small increase in dengue in Niterói, according to the researchers.
The number of cases was also 90% lower than before the Wolbachia mosquitoes were deployed - and “nothing like what was happening in the rest of Brazil,” said Katie Anders from the World Mosquito Program.
The fact that the city did so well showed that “Wolbachia can provide long-term protection for communities against the increasingly frequent dengue outbreaks we are seeing globally,” Anders said.
The researchers said they have partnered with the Brazilian government to build a facility to produce mosquitoes with Wolbachia in the hope of protecting millions of people.
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