Nha Trang (Vietnam) (AFP)
Hundreds of dead in the Philippines, sick hospitals in Vietnam, Malaysia, Burma and Cambodia: Dengue epidemic ravages Southeast Asia, and scientists tackle the spread of the virus with experimentation tested in nine countries including Vietnam.
Led by the global mosquito control program, it consists in injecting mosquitoes into the laboratory bacteria, wolbachia, which significantly reduces a possible transmission to humans of dengue fever - but also other viruses such as Zika, Chikungunya or yellow fever.
Once the insects are released into the wild, they reproduce with the vector species of these diseases. Babies, carriers of the bacteria, have only a small chance to transmit the virus.
In Vietnam, the first results on dengue fever - the main virus transmitted by mosquitoes worldwide - are promising.
"We have seen a significant drop in cases" as a result of this experiment, says Nguyen Binh Nguyen, one of the coordinators of the project in Vietnam.
Last year, his team released about half a million mosquitoes carrying wolbachia in Vinh Luong, an overpopulated district in the south of the country, which is particularly vulnerable to dengue fever.
- 86% fewer cases -
Since then, cases have decreased in this area by 86% compared to the nearby resort of Nha Trang, ensures Nguyen Binh Nguyen.
And the inhabitants are relieved because if the insects continue to circulate, the majority are now carriers of wolbachia.
"I feel more comfortable now (...) but I still have to be careful," said Cong Thi Thu, an accountant who, with her two children, was the victim of a severe crisis. dengue in 2016.
Dengue, whose symptoms (joint pain, high fever, vomiting ...) are similar to an ILI, affects more severely children, especially young girls, although scientists do not know why.
No specific treatment exists.
- More than 1,800 deaths -
Since the beginning of the year, this disease has hit Southeast Asia hard: at least 670,000 people have been infected and more than 1,800 have died in the region, according to data compiled by AFP from figures from the World Health Organization (WHO) and health authorities in these countries.
The cause is high temperatures and a new strain of the virus that spreads rapidly among non-immune populations.
Mosquitoes that transmit dengue fever to humans tend to thrive in warm, humid urbanized areas where stagnant water is abundant.
Half of the world's inhabitants live in high-risk areas, mainly in Latin America, Africa and Asia.
Disruption of ecosystems, displacement of people and goods due to globalization, rampant urbanization without sanitation, global warming: "the cocktail is perfect for the epidemic" is progressing very quickly, says Rachel Lowe, assistant professor at the London School of Hygiene & Tropical Medicine.
There are four strains of the virus. An infected person is immune for life against the person who has infected. But if it is affected by another form, the symptoms are often much larger.
- Vaccine or bacteria? -
There is a dengue vaccine developed by the Sanofi Pasteur laboratory and approved for use in some 20 countries and in the European Union. But it is controversial. In the Philippines, its failed deployment in 2016 resulted in the deaths of dozens of children and led to its ban.
The scientific community is now all the more interested in the bacterium Wolbachia, as large-scale insecticides sprayed in parts of South-East Asia are only effective in the short term and mosquitoes develop resistance to these products.
Present in 60% of insect species, wolbachia was first discovered in the 1920s by mosquitoes living in the drainage system under Harvard University in the United States.
Other work, particularly in Malaysia and Singapore, uses wolbachia, but the method is different: researchers infect male mosquitoes with it, making them "incompatible" with uninfected females and thus preventing eggs from being laid. grow and hatch.
In the absence of large-scale studies, it is still too early to comment on the real success of experiments using this bacterium.
"At the end of the day, our goal is to make sure that it will lead to a real reduction of the disease," said Raman Velayudhan, WHO coordinator of the global dengue fever program.
© 2019 AFP