Key Points

• Between January 1 and December 31, 2025, 309 cases of acute hepatitis A were diagnosed and reported in the Auvergne-Rhône-Alpes region. This number of cases represents a sharp increase compared to 2024 (+91%).
• For the fourth consecutive year, the regional reporting rate has been higher than the national rate (3.7 cases vs. 2.6 cases per 100,000 residents).
• In 2025, the seasonal peak occurred earlier, driven primarily by the Rhône department, where an outbreak took place during the summer.
• The demographic and clinical characteristics of the cases are similar to those of 2024: male-to-female ratio of 1.2, median age of 30 years, 71% of cases presenting with jaundice, and a hospitalization rate of 56%. However, identified risk exposures in the 2 to 6 weeks before the onset of symptoms were less frequent (57% vs. 70% in 2024), which was partly due to the outbreak in the Rhône.
• The increase in the number of cases at the regional level was greatest in Isère and the Rhône.
• An outbreak occurred in the Rhône department during the summer of 2025, with 93 cases reported between July 1 and September 30—six times more than during the same period in 2024. The majority of cases had visited Lyon’s 7th arrondissement, although no common risk exposure could be identified.