Key Points

• 40 cases reported in 2025 in Auvergne-Rhône-Alpes: on the rise since mandatory reporting began in 2021;
• Sex ratio (male to female) of 3.4;
• Median age of 51 years (minimum 22 years; maximum 81 years);
• 90% of cases were hospitalized;
• Most common neurological manifestations: meningitis (30% of cases), encephalitis, or meningoencephalitis (50% of cases);
• Haute-Savoie, the historical epicenter of the disease, accounts for half of the region’s cases;
• Other areas where the virus circulates identified in the region: the Pilat Mountains, the Bois Noirs Massif (Loire), and Trièves (Isère);
• Exposure to ticks was found in all cases, with 25 patients (63%) reporting a tick bite;
• Wearing long clothing and using repellents are the main preventive measures to avoid tick bites and reduce the risk of pathogen transmission.