Half of the world’s population is now exposed to dengue fever. Several experts from the World Health Organization (WHO) reiterated this estimate on Wednesday, August 2, as part of an online information meeting on dengue fever, warning against the progression of this viral infection transmitted to humans via certain species of mosquitoes.
“More than 130 countries are affected by dengue fever, which has now affected all continents, including Europe since the 2010s,” noted Raman Velayudhan, head of the veterinary public health, vector control and environment unit at the United Nations organization. “Dengue is a disease that poses a strong challenge to global health, the progressive expansion of which seems to know no bounds,” added Ibrahima Socé Fall, Director of the Global Program for the Control of Neglected Tropical Diseases at WHO.
With 5.2 million cases in 129 countries, 2019 was the deadliest year in the past 20 years. After a relative respite in 2020-2021 during the Covid period, the world is on track to register “more than four million” cases in 2023, which will mainly depend on the monsoon season in Asia, said Raman Velayudhan, the combination of rain and high temperatures favoring the hatching of mosquito eggs.
Majority of asymptomatic cases
On the American continent, more than three million cases have already been recorded since the beginning of the year. While Brazil concentrates most of the cases, the disease is now spreading to states further south, such as Bolivia, Paraguay and Peru, which were previously too cold for Aedes aegypti, the main vector of the disease in this region. part of the world.
The progression of this mosquito – and its cousin Aedes albopictus – is in fact largely driven by global warming, via the general increase in temperatures and changes in precipitation patterns. In a study published in April in the journal Plos Neglected Tropical Diseases, American researchers estimated that in most Brazilian states, the epidemic potential would increase by 10% to 20% by 2040.
Asia, and more particularly Southeast Asia, is one of the most affected regions of the world and accounts for 70% of the global mortality burden. In Bangladesh, some 240 deaths have been recorded since the beginning of the year, and 234 in the Philippines. Although the vast majority of cases are asymptomatic – which complicates the epidemiological monitoring of the disease – dengue fever can prove fatal. The first symptoms of the disease – high fever, severe headache, muscle pain, nausea – are not specific to it and can be confused with those of other pathologies. Only screening can then confirm the presence of the virus.
Disease endemic to the West Indies
In Europe, the disease made its appearance with the arrival of Aedes albopictus, a mosquito with extraordinary adaptability. Since then, Spain, Italy and France are considered hotspots. In France, the year 2022 was marked by an epidemic deemed “exceptional” by Public Health France, with 378 imported cases and nine episodes of indigenous transmission totaling 66 cases of contamination on French soil.
In 2023, no indigenous cases have yet been reported, but 227 imported cases have already been reported since May 1, including 77 in Ile-de-France, 35 in New Aquitaine, 24 in Occitanie, 22 in Auvergne-Rhône-Alpes and 22 in Provence-Alpes-Côte d’Azur. A third of these travelers who tested positive for the dengue virus were returning from the West Indies, where the disease has been endemic for more than ten years. Since the beginning of the year, more than 250 cases have been notified to the Regional Health Agency of Martinique and 425 clinically suggestive cases of dengue have been recorded by that of Guadeloupe.
In the Provence-Alpes-Côte d’Azur region, where the Interdepartmental Agreement for Mosquito Control of the Mediterranean Coast operates, 28 cases have been reported since the start of the season and 20 treatments have been carried out. “But the biggest is ahead of us and things are accelerating with the return from vacation,” says Grégory L’Ambert, head of the preventive control center against Aedes albopictus.
In the Occitanie and Nouvelle-Aquitaine regions, where the company Altopictus is responsible for mosquito control around proven cases of dengue fever, 106 surveys had been carried out by August 2, leading to 87 treatments of areas deemed potentially at risk, either by spraying insecticide or larvicide, or by the massive installation of traps in sensitive places, for example on the banks of rivers. By way of comparison, on the same date the previous year, only 47 surveys and 34 treatments had been activated. “The number of imported cases increases the risk of indigenous cases but does not prejudge the balance sheet of the end of the season”, warns Charles Tizon, director of Altopictus. In May and June, the company’s monitoring network found two to three times more mosquito eggs than the previous year, due to regular rains and higher than normal temperatures.