“The risk should end quickly”, how do indigenous dengue outbreaks impact blood donations?

Since the start of 2024, mainland France has recorded a record number of cases of indigenous dengue fever, with 85 infections localized in the south. People living in affected areas may therefore be refused to donate blood, to prevent transmission of the virus.

Patrice donates blood whenever he can.

The 51-year-old from Nîmes says he has been a regular donor for at least five years, eight to ten times each year. “For me, it’s a free and obvious gesture”he maintains. This Saturday, November 23, Patrice is going to the Maison du don in Nîmes, at the University Hospital. As usual. But this time, he is asked a new question.

“I was asked if I had been to Montpellier or Fréjus in the last three weeks, in which case I would not have been able to donate blood. I was told that it was because it was There were outbreaks of dengue fever there.he says.

Indeed, according to information transmitted by the regional branch, PACA, of the French Blood Establishment (EFS), four cities in the south of France are currently hotbeds of autochthonous dengue fever: Fréjus and Ramatuelle in the Var, Vallauris in the Alpes-Maritimes, then Montpellier.

The Occitan city is the last outbreak to have been detected, last October. “The risk should end quickly”however reassures Doctor Catherine Lazaygues, regional manager of samples at EFS PACA.

Since the start of 2024, at least 85 indigenous cases of dengue fever were localized in mainland France. This is a record figure, previous was 66, in 2022. And if we look at the map provided by Public Health France, we see that these outbreaks are concentrated only in the south of France

This is nothing trivial. Walls characterized as a “tropical flu”, lDengue fever is a viral disease transmitted by the bite of mosquitoes of the genus Aedes. These are mainly present in tropical and subtropical climates. This is why, in mainland France, infected people are particularly infected when traveling abroad.

However, France also experiences cases of autochthonous dengue fever, that is to say infections contracted on the territory without any link to any travel. These outbreaks are mainly located around the Mediterranean rim, a region conducive to the proliferation of mosquitoes due to the hot climate.

“As soon as a case of indigenous dengue fever is confirmed, mosquito control actions are carried out in the area to prevent any spread”indicates Catherine Lazaygues.

As for the symptoms of dengue, the doctor assures that they are not always noticeable. According to her, some people may be asymptomatic. Otherwise, they boil down to a flu-like state, between fever, fatigue and severe muscle pain.

“Without being always fatal, it is a disease which can nevertheless present serious forms in immunocompromised or elderly people, for example”also specifies Catherine Lazaygues. She adds: “And since blood donations make it possible to transfuse rather fragile and vulnerable people, we are careful not to bring them a virus that could make them worse.”

They are therefore asked not to donate blood for at least 28 days. This delay then allows us to be sure that they are no longer carrying the virus.

Catherine Lazaygues, regional head of sampling at EFS Paca

Indeed, the risk of transmission of dengue fever is through mosquito bites and therefore through the bloodstream. Thus, to avoid taking blood from contaminated people, the French Blood Establishment has the right to refuse any person who has traveled in an area identified as a dengue outbreak.

“On asks them not to donate blood for at least 28 days. This delay then allows us to be sure that they are no longer carrying the virus.details Catherine Lazaygues. In certain situations, screening tests can also be carried out so as not to miss potential donors.