Intense fatigue, high fever, muscle pain for the mildest symptoms. Bleeding, drop in blood pressure leading to death for the most serious form. In 2024, nearly 12.5 million people will contract the dengue virus, a disease transmitted by Aedes mosquitoes. A record number, dethroning 2023, when 6.5 million cases were reported worldwide. “The rapid spread observed in recent years is an alarming trend,” said Dr Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization (WHO).
Yet another consequence of global warming
Although dengue was initially prevalent in tropical and subtropical areas of the world, the 2000s changed the situation. Between 2000 and 2019, the number of people infected globally increased from 500,000 to 5.2 million. And in 2010, Europe recorded its first two indigenous cases. Due to the globalization of the economy, urbanization and global warming, dengue fever has been able to reach new geographical areas over the years. According to Professor Sophie Yacoub, head of the dengue research group at the University of Oxford, interviewed by The Guardianthese factors “are at the origin of transmission in Europe, China as well as in all the southern states of America”.
Especially since the warming of the Earth is far from displeasing mosquitoes. Among the species that can transmit dengue are Aedes Aegypti and Aedes Albopictus, more commonly known as the tiger mosquito. An insect capable of surviving during heat waves, and whose reproductive cycle is accelerated during these increases in temperature.
But beyond helping these mosquitoes continue their lineage, climate change can also cause extreme weather events, such as flooding, to create new breeding grounds. Since in addition to perfectly adapting to urban environments, the tiger mosquito only requires a tiny amount of stagnant water to reproduce. A vicious circle then follows. When a mosquito bites a person infected with the virus, it enters the insect, becoming infected in turn. The next person bitten by the mosquito will then see the virus enter their bloodstream and cause an infection.
A link with obesity and diabetes?
According to scientists, obesity rates and other chronic health problems also make the population more venerable. Among other things, there are risk factors similar to Covid-19. “As dengue affects many countries where obesity and diabetes are also on the rise, these two epidemics are somewhat colliding. In Vietnam, we are seeing a high rate of obesity among our adolescents, and this They are the ones who come to the hospital,” explains Sophie Yacoub.
Another aggravating factor: the presence of the four dengue serotypes. The increase in the number of cases in Brazil could be partly explained by the fact that the four serotypes, the “versions” of the virus, appear to be circulating simultaneously for the first time. In fact, each serotype interacts differently with the antibodies present in the body. Thus, infected people develop immunity against the serotype they encounter for the first time. But during a second infection with a different serotype, the body can produce antibodies directed against the first serotype encountered. However, these will bind to the particles but will not succeed in neutralizing them. Instead, an extreme immune response will be created, which may result in organ breakdown.
Although no treatment currently exists for dengue fever, scientists are actively working on the issue. In the meantime, some are opting for traditional remedies such as papaya tea, despite the lack of hard evidence as to its true effectiveness.