French Guiana, gripped by an alarming dengue epidemic

This year, the mosquito is especially lively. A particularly acute dengue epidemic is affecting French Guiana, with an average of 800 new cases registered each week, as announced by health authorities on Monday, February 12. According to French public health authorities, 5,800 cases have been registered in the Amazon department of 300,000 inhabitants since the beginning of 2023, of which 2,996 have occurred in 2024. This is an unprecedented figure in the last 20 years.

“The epidemic threshold has been surpassed in the Antilles and throughout the Caribbean. But for French Guyana, it is quite recent,” epidemiologist Antoine Flahault, director of the Institute for Global Health at the Faculty of Medicine of the University, told France 24. of Geneva.

In its latest report, the Regional Health Agency (ARS) indicated on February 1 that at least 253 patients had been hospitalized, including ten “admitted to intensive care.” “Four people who had tested positive for dengue had died, one of them directly related to dengue,” the ARS said.

The Regional Health Agency has opened a specific reception area in the emergency department of the Cayenne Hospital Center (CHC) for people with symptoms, so that they can be treated immediately if necessary.

For now, the impact on the Guyanese health system remains “relatively limited.” At the beginning of February, the infection had only generated “between 8 and 10% more activity” in the emergency departments of the Kourou and Cayenne hospitals.

An aggressive virus for sickle cell disease patients

“The majority of infected people present only mild symptoms, or none at all,” the Pasteur Institute states on its website. In its classic form, dengue manifests itself as “high fever often accompanied by headaches, nausea and vomiting” that lasts from two to seven days.

But in the most severe cases, this disease endemic to tropical areas can cause hemorrhages or shock syndromes that can lead to death. For people with sickle cell disease in particular, the dengue virus can be very aggressive.

“Dengue is generally benign […] It is sometimes called tropical flu, but it can be dangerous for some people,” Professor Narcisse Elenga, head of the pediatric service and head of the integrated sickle cell anemia center at the Cayenne hospital, warned Guyane La Première. In French Guiana, the 10% of the population carries the gene that transmits the disease, according to the Observation régional de santé.

“Domestic” mosquitoes in gardens

In tropical and intertropical areas such as French Guiana, dengue epidemics are common. They repeat every three or five years and usually last between 12 and 18 months. Viral waves vary in intensity.

Two of the four existing dengue genotypes (DEN-2 and DEN-3) circulate at the same time in the region, which may have contributed to the intensification of the epidemic, since a person is immune after becoming infected with dengue DEN-2 You can get infected again if you contract dengue DEN-3 this time.

Climatic conditions also contribute to the intensity of the epidemic. According to the World Health Organization (WHO), dengue is increasing worldwide as a result of climate change. In French Guiana, the epidemic has been enhanced by the rainy season, which has increased the number of areas of stagnant water and, therefore, breeding sites.

Dengue is generally transmitted by the bite of the Aedes mosquito, nicknamed the tiger mosquito. “They are mosquitoes that do not travel very far, they only have a flight perimeter of 70 or 100 meters,” explains Antoine Flahault, who describes them as “domestic” mosquitoes because they live near houses. “They are raised in the garden, normally under the pots in the gardens,” the epidemiologist explains ironically. “You must remove the water from under the saucers, do not water the plants, and try to avoid these small accumulations of stagnant water, which will cause mosquitoes to multiply in their direct environment,” he recommends.

To combat the proliferation of the dengue mosquito, a surveillance unit was created on February 6 in which the State services and the Territorial Collective of Guyana (CTG) participate, according to the prefect of French Guiana, Antoine Poussier. A decree has been signed to accelerate the removal of unused vehicles, of which there are many on the sides of the roads and “which constitute breeding sites for mosquitoes that facilitate the spread of dengue.”

The CTG has promised to “increase its human and material resources” in the field of the fight against mosquitoes, for which it is responsible. Chemical fumigation operations are not free of side effects. Mosquito control operations are usually carried out at night, as the sprayed product can cause health problems. Furthermore, warns the Pasteur Institute, “insecticides can also be used, but their massive use can cause resistance phenomena in mosquito populations, which makes them less effective.”

A “promising” Brazilian vaccine

Although there is no specific treatment against dengue, vaccines have been developing for several years. But the French authorities still do not recommend them.

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 at the moment due to adverse effects.” In a report published in January 2019 on this vaccine, Dengvaxia, the French National Health Authority found “an increased risk of hospitalization and severe dengue” in people who had not previously contracted the disease, “in particular young children.”

In Brazil, where in the first five weeks of the year 395,103 probable cases of dengue and 53 deaths related to this disease were recorded, a free vaccination campaign was launched on February 9. Using the Qdenga vaccine, produced by the Japanese laboratory Takeda, the campaign begins with children aged 10 and 11, and will gradually extend to patients up to 14 years old.

This vaccine “has the particularity of being usable by everyone, but it does not protect against all types of dengue”, as reported by Guyane La première.

A third vaccine, currently being studied, raises great hopes. This is the Brazilian vaccine Butatan-DV, which Antoine Flahault describes as “very promising.” The single-dose vaccine is said to protect against all four types of dengue. Initial results from trials conducted with 16,235 people in Brazil, which began in February 2016, show a high level of efficacy, 90% in people over 18 years of age and 77.8% in children over 7 years of age. However, its commercialization is not expected until 2025, when it will be examined by health authorities, who will decide whether to give the green light to its commercialization.

This article was adapted from its original in French