Key points

Acute Respiratory Infections (ARI)

• Winter surveillance of acute respiratory infections (ARI) during the 2024–2025 season was characterized by two epidemic waves: the first in September/October 2024 linked to the circulation of the SARS-CoV-2 virus, and the second, more significant wave in December/January 2024 linked to a resurgence of bronchiolitis and influenza cases.

Influenza

• The influenza epidemic began earlier and lasted longer than the previous year’s. It lasted 12 weeks.

• The epidemic reached high levels of morbidity and mortality, approaching those observed during the 2022–2023 epidemic, the most severe ever recorded.

• This epidemic was characterized by the co-circulation of type A (primarily A H1N1) and type B viruses.

• The influenza vaccination rate was only 57.7% among people aged 65 and older and was lower than in previous years. Among severe cases admitted to intensive care, 75% were unvaccinated.

COVID-19

• The Covid-19 epidemic began in early September 2024 and continued through the end of October 2024. It was less severe than previous waves.

• Among the severe cases reported by intensive care units, 89% were unvaccinated.

• The Covid-19 vaccination rate among healthcare workers in long-term care facilities (LTCFs) remained very low (5%) given the risk of viral transmission within these facilities.

Bronchiolitis

• In Normandy, the 2024–2025 bronchiolitis epidemic was relatively brief (six weeks), and its intensity remained moderate.

Acute gastroenteritis

• In Normandy, indicators for acute gastroenteritis (AGE) showed a moderate increase starting in mid-December (week 50), peaking in late December (week 52).

• Activity then gradually declined, stabilizing at a moderate level by late January (week 04), and then at a low level by mid-May (week 21).