Tick encephalitis: Why does the number of cases explode in France?

62 cases of tick encephalitis were identified in France in 2024, according to the latest assessment published by Public Health France. This represents an increase of 60 % compared to 2023 (39 cases) and 77 % compared to 2022 (35 cases).

The disease remains rare compared to other infections transmitted by ticks, such as Lyme Borreliosis (several tens of thousands of cases per year in France). But this rapid progression draws attention, especially as tick -eating (TBE) can cause severe neurological forms.

Tick encephalitis: an unprecedented increase in cases in France

But why this sudden increase?

Contrary to what one might think, this outbreak does not necessarily reflect an explosion of the virus in France. It is partly explained by a positive phenomenon: improving the surveillance system. Since 2022, tick encephalitis has been one of the mandatory declaration diseases. So, doctors report more cases, including those who have been ignored before because they manifested themselves in simple influenza symptoms.

But it would be reductive to see only an administrative question. Several environmental factors play a role:

• Global warming: softer winters and earlier spring promote the survival and multiplication of ticks.
• The modification of ecosystems: fragmentation of forests, proliferation of certain animals tanks (rodents, deer).
• New lifestyles: return to nature, the popularity of hikes, camping, picking … so many activities that mechanically increase contacts with ticks.

What are the most affected profiles?

In 2024, almost 9 out of 10 cases (88.7 %) were linked to infections contracted in France. It is therefore no longer just an “imported virus” from central or eastern Europe, but a disease that is gradually installed on our territory.

The most exposed professions are logically those working in contact with nature: foresters, farmers, breeders, loggers, pickers. According to Public Health France, a quarter of patients (25.8 %) belong to these professional categories.

As for the geographic areas, the most concerned regions are located in eastern France, notably the Grand Est and Burgundy-Franche-Comté, border with Germany and Switzerland where the disease has long been endemic.

Food transmission: a risk that is still unknown

If the majority of contaminations arise after a tick sting, a few cases have been attributed to the consumption of raw milk or non -pasteurized cheeses from infected animals.

In 2020, a contamination center had been identified in Haute-Savoie, linked to the consumption of raw dairy products (ANSES). The health agency therefore recommends prudence, especially for children, the elderly or immunocompromised: favor pasteurized products in areas at risk.

What symptoms after a tick bite?

The difficulty with tick encephalitis is that it does not always manifest itself. Many people stuck by infected tick will not develop any symptoms.

In others, the disease evolves in two phases:

1. Initial phase (5 to 15 days after the bite): fever, fatigue, muscle pain, headache. In short, a painting that looks like a classic flu.
2. Neurological phase (in around 30 % of symptomatic cases): more serious attacks with meningitis, encephalitis, even paralysis. The consequences can be heavy: memory disorders, chronic fatigue, persistent pain.

Unlike Lyme borreliosis, there is no specific curative treatment against the tick encephalitis virus. Management is only symptomatic, which strengthens the importance of prevention.

But then, what solutions to protect yourself?

A vaccine exists, but it is not for everyone

There is indeed a tick encephalitis vaccine. Used massively in Austria, Germany and Switzerland, it has made it possible to greatly reduce the number of cases in these countries.

In France, it is not recommended to the entire population. The High Authority for Health (HAS) advises vaccination only for:

• people who live or work in identified risk areas,
• Travelers going to endemic regions of central and eastern Europe.

How to protect yourself effectively?

Faced with the progression of tick encephalitis, prevention remains the most effective weapon. The basic advice is simple, but essential:

• Dressing properly: long pants, long sleeves, light clothes to better locate ticks.
• Use skin repellents approved against ticks.
• Inspect your skin after an outing in nature, especially the hot and humid areas (armpits, folds, scalp, behind the ears).
• Quickly remove a tick with a tick (available in pharmacies), never with fingers or alcohol.
• Avoid raw dairy products in risk areas.

These simple gestures considerably reduce the risk of infection.

Tick encephalitis: should you worry?

Today, tick encephalitis remains a rare disease in France: a few dozen cases per year. But its progression must alert us, because it testifies to both climate change, the evolution of ecosystems and the need to adapt our prevention habits.

For experts, it is not a question of yielding to panic, but of adopting an enlightened vigilance. The good news is that we already have tools to protect ourselves: information, simple gestures, targeted vaccination.

NAMELY

According to the latest annual report of the European Disease Prevention and Control Center (ECDC), in 2022, 20 countries in the European Union/EEE reported 3,650 cases of tick encephalitis, 3,516 of which were confirmed, which represents a notification rate of 0.81 cases per 100,000 inhabitants, up 14 % compared to 2021.