Key Points

Acute respiratory infections (ARI)

• A season characterized by two successive peaks: one in late December, linked to the bronchiolitis outbreak and COVID-19, and another in late January, due to the flu outbreak.

• Impact on outpatient and hospital care provision was lower than in the 2022–2023 season.

Flu

• A flu season of typical duration from late December to late February, lasting 10 weeks.

• Moderate scope and intensity in community practice:

  • 1.5 million consultations for flu-like illness (Sentinelles network)

  • Flu-like symptoms accounted for 18% of SOS Médecins consultations at the peak of the epidemic in late January (S05-2024)

• Moderate severity with 14,000 hospitalizations following visits to the emergency room.

• Predominant circulation of A(H1N1)pdm09 viruses.

• Vaccination coverage estimated at 47.1% among at-risk individuals targeted for vaccination, and 54.0% among those aged 65 and older, lower than in 2022–2023.

Bronchiolitis

• Early epidemic in mainland France, beginning in mid-October (Week 42, 2023), i.e., 4 weeks earlier than usually observed, and ending in early January (Week 1, 2024).

• Typical epidemic duration of 12 weeks.

• The proportion of hospitalizations for bronchiolitis among all hospitalizations following emergency department visits in children under 2 years of age was 44.3% at the peak of the epidemic in late November (Week 48 of 2023).

• Intensity comparable to that of epidemics prior to the emergence of COVID-19. Intensity lower than that of last season (2022–2023), which was particularly severe.

• An immunization campaign using the monoclonal antibody nirsevimab (Beyfortus®), a preventive treatment for RSV infections in infants, was launched in mid-September 2023.

COVID-19

• The dynamics and intensity of the epidemic waves were comparable to those of 2022–2023.

• Indicators began to rise in July 2023, with two peaks in September and December. A decline has been observed since mid-December, with indicators at low levels since mid-February.

• Peak share of hospitalizations in December (3.3% in S50-2023).

• The JN.1 variant has been the predominant strain since late November 2023.

• Vaccination coverage estimated at 30.2% among people aged 65 and older following the vaccination campaign from October 2023 to February 2024.