Health. Tick-borne encephalitis: the worrying contamination from raw milk cheese confirmed

"This is a mode of transmission not previously observed in France," the French National Agency for Food, Environmental and Occupational Health and Safety (ANSES) told us about the outbreak of tick-borne encephalitis cases that has occurred since 2020. And for good reason: this rare disease (usually 35 cases per year in France) has experienced a real outbreak in recent years. It is caused by the TBE virus ( tick-borne encephalitis ), which belongs to the same family as the West Nile virus or dengue fever . According to Santé publique France, it is usually transmitted through tick bites, and rarely - until now - through the ingestion of raw goat or sheep milk, after these animals have themselves been bitten.

But things have changed: "Since 2020, cases linked to the consumption of raw milk products […] have been reported," says ANSES, which specifies that this is new in the country. The result is a "geographical extension of the virus's presence and an increase in the number of cases in Europe, all transmission routes combined."

Health authorities are warning: this disease can be serious. Of 71 serious cases studied between 2021 and 2023, 94% required hospitalization, and after-effects persisted in 30 of them, including one of the four infected children.

In 2020, "native" cases occurred in departments that had already been affected previously: Haute-Savoie, Haut-Rhin, Bas-Rhin, Loire, Ain, Puy-de-Dôme, Isère, and Savoie. Until then, traces of tick bites had always been observed. But Ain recorded a record number of 43 cases that year, more than for the entire country in a full year. Other departments that had been spared before 2020 were quickly affected, still in eastern France: Rhône, Ardèche, Cantal, Doubs, Vosges, Meurthe-et-Moselle, Marne, Moselle, and Haute-Saône.

In the Rhône region, a link was quickly made to a rare collective food poisoning, attributed to fresh goat cheese made from raw milk from a local herd. But more importantly, ANSES notes that, in the Ain region as well, the 43 sick people had consumed raw goat cheese from the same farm. They all displayed flu-like symptoms or meningitis.

In its report published on July 8, ANSES calls for increased collaboration between farmers and scientists to improve detection and better prevent the risk of infection: "Many questions remain about the mechanisms of virus circulation and transmission," explains Elsa Quillery, co-coordinator of the text. She adds that "research must be conducted on […] the strains circulating in France, the risk factors for transmission, and the impact of milk components and milk processing methods on the persistence of infectious viruses in dairy products." The virus is now present throughout France - with the exception of the Mediterranean region.