This year, the mosquito is showing itself to be particularly lively. A particularly acute dengue epidemic is affecting Guyana, with 800 new cases declared on average per week, health authorities announced on Monday February 12. According to Public Health France, 5,800 cases have been recorded in the Amazon department of 300,000 inhabitants since the start of 2023, including 2,996 already in 2024. Unheard of in twenty years.
“The epidemic threshold has been exceeded in the Antilles and throughout the Caribbean. But for Guyana, it is quite recent,” confirms epidemiologist Antoine Flahault, director of the Institute of Global Health at the Faculty of Medicine of the University of Geneva on France 24.
In its latest bulletin, the Regional Health Agency (ARS) specified on February 1 that at least 253 patients had been hospitalized, including ten “admitted to intensive care”. “Four people who tested positive for dengue died, one of whom was directly linked to dengue,” indicated the ARS.
The Regional Health Agency has opened a dedicated emergency reception at the Cayenne Hospital Center (CHC) for people with symptoms in order to take care of them immediately if necessary.
For the moment, the impact remains “relatively limited” on the Guyanese health system. At the beginning of February, the infection had only generated “8 to 10% more activity” for the emergencies of the Kourou and Cayenne hospitals.
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An aggressive virus for people with sickle cell disease
“The majority of infected people have only mild or no symptoms,” the Institut Pasteur indicates on its website. In its classic form, dengue fever manifests itself “by the appearance of a high fever often accompanied by headache, nausea and vomiting” lasting two to seven days.
But in the most serious cases, this disease endemic to tropical areas can cause bleeding or shock syndromes which can lead to death. For people with sickle cell disease in particular, the dengue virus can be very aggressive.
Also read: Sickle cell anemia, a disease poised to become a public health issue in France
“Dengue fever is generally benign [...] It is sometimes called tropical flu but its evolution is dangerous for certain subjects,” warns on Guyane La Première Professor Narcisse Elenga, head of the pediatric department and head of the integrated sickle cell center. at the Cayenne Hospital Center. However, in Guyana, 10% of the population carries the gene that transmits this disease, according to the Regional Health Observation.
“Domestic” mosquitoes in gardens
In tropical and intertropical areas, such as Guyana, dengue epidemics are common. They come back every three to five years and generally last 12 to 18 months. Viral waves are more or less intense.
Two dengue genotypes (DEN-2 and DEN-3) out of the four existing ones are circulating at the same time in the region, which may have contributed to the intensification of the epidemic, because a person immunized after being infected by the dengue DEN-2, could be infected again if she catches dengue DEN-3 this time.
Climatic conditions also contribute to the intensity of the epidemic. According to the World Health Organization (WHO), dengue fever is on the rise worldwide due to climate change. In Guyana, the epidemic was favored by the rainy season, which increased the number of areas of stagnant water and therefore the larval breeding sites.
Dengue fever is generally transmitted by the bites of the Aedes mosquito, nicknamed the tiger mosquito. “These are mosquitoes that don't travel a lot, they have a flight radius that only goes up to 70 or 100 meters,” specifies Antoine Flahault, who describes them as 'domestic' mosquitoes because they live close to houses. “You raise them in your garden, generally under flower pots in gardens,” explains the epidemiologist ironically. “You really need to remove the water under the saucers, do not water your plants, try to avoid these small collections of stagnant water which will cause mosquitoes to swarm in your direct environment,” he recommends.
Also read: The tiger mosquito, a threat to public health in France?
To combat their proliferation, a monitoring unit bringing together state services and the Territorial Collectivity of Guyana (CTG) was activated on February 6, indicated the prefect of Guyana Antoine Poussier. An order was signed to speed up the removal of end-of-life vehicles, which are numerous on the roadsides and “which constitute breeding grounds for mosquitoes facilitating the spread of dengue”.
The CTG promised to “increase its human and material resources” in the field of mosquito control, for which it has competence. Chemical spreading operations which are not without side effects. Mosquito control generally takes place at night because the product released can cause health problems. Furthermore, warns the Pasteur Institute "insecticides can also be used but their massive use can generate resistance phenomena among mosquito populations, making them less effective".
A “promising” Brazilian vaccine
Although there is no specific treatment for dengue fever, vaccines have been developed for several years. But they are not yet recommended by the French authorities.
Sanofi has developed a vaccine, but "it is not recommended in most cases", explains Antoine Flahaut, adding that it "has proven disappointing and complicated to handle for the moment due to adverse effects" . In a report published in January 2019 on this vaccine, Dengvaxia, the High Authority of Health noted “an increase in the risk of hospitalization and severe dengue” in people who have not contracted the disease in the past, “in particular young children.”
In Brazil, where 395,103 probable cases of dengue and 53 virus-related deaths were recorded in the first five weeks of the year, a free vaccination campaign was launched on February 9. Carried out with the Qdenga vaccine, produced by the Japanese laboratory Takeda, it begins with children aged 10 and 11, and will gradually be extended to patients up to the age of 14.
This vaccine “has the particularity of being usable by all, but does not protect against all types of dengue”, we can read on Guyane La Première.
A third vaccine, currently under study, raises a lot of hope. This is the Brazilian Butatan-DV vaccine, “very promising” according to Antoine Flahault. The single-dose vaccine would protect against all four types of dengue. Initial results from trials carried out on 16,235 people in Brazil, and started in February 2016, show high effectiveness, at 90% in those over 18 years old and 77.8% in children over 7 years old. . But it should not be marketed before 2025, the time to be examined by the health authorities who will decide to give the green light to its marketing.
With AFP
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