It's not just Lyme disease: this tick-borne virus is even more serious

This disease, which is affecting more and more people in Europe, including in France, is worrying health authorities.

It's summer, the sun is shining... and ticks are out. The problem is that these little creatures can transmit several diseases, including Lyme disease, which affects around 50,000 people a year in France, according to the Pasteur Institute . Ticks can also transmit a much rarer but potentially very serious disease.

This disease is becoming increasingly common: an " increase in the number of cases " has been observed in several countries, including France, according to ANSES (French National Agency for Food, Environmental and Occupational Health and Safety), which recently published the results of an expert report on the subject. Around thirty cases are reported each year in France. In 2023, 39 cases were recorded.

According to ANSES, in addition to the increase in the number of cases, "several factors raise fears of an increased risk of virus transmission in France." First, " the virus is expanding its area of circulation ." While cases were previously limited to Alsace, cases are now being " reported outside " this region. In Europe, the disease is " endemic " in Germany, Austria, Norway, Sweden, and Finland.

Then, while tick-borne encephalitis, as its name suggests, is generally transmitted by ticks, " cases linked to the consumption of raw milk products, a mode of transmission not previously observed in France, have been reported ," notes ANSES. Milk from animals affected by ticks can indeed be contaminated. ANSES also specifies that " raw milk and dairy products made from raw goat's milk appear to present a greater risk of transmission than dairy products from other animals ." For all these reasons, tick-borne encephalitis " is a growing concern in France ."

In infected individuals, tick-borne encephalitis is symptomatic in 10 to 30% of cases. These are usually flu-like symptoms. However, " among symptomatic individuals, 20 to 40% present neurological signs similar to meningitis, which can lead to long-term after-effects and a loss of autonomy ," explained Elsa Quillery in the ANSES expert report.

Fortunately, it is possible to reduce the risk of becoming infected with tick-borne encephalitis. First, avoid tick bites by wearing long clothing and using repellent when walking in nature. For those particularly at risk of being infected, such as forestry workers or livestock farmers, vaccination against the virus is available. Ticks are most active from March to November.