Key Points

• The incidence of bronchiolitis among children under two years of age is on the rise in mainland France as well as in the overseas departments and regions.

• In mainland France, four regions have entered the pre-epidemic phase (Grand-Est, Normandy, Nouvelle-Aquitaine, and Pays-de-la-Loire). In the overseas departments and regions, French Guiana has also entered the pre-epidemic phase.

• The increase in bronchiolitis-related activity observed in mainland France continues across all syndromic surveillance indicators: for SOS Médecins medical consultations, for emergency room visits, and for hospitalizations following emergency room visits for bronchiolitis. These increases are comparable to those observed during the same period in the two previous years, indicating another early onset of bronchiolitis-related activity.

• The detection rate of RSV (respiratory syncytial virus) in nasopharyngeal swabs from all age groups in hospitals remains very low (<1%). This rate is 4.7% in samples collected in community settings. Other viruses capable of causing bronchiolitis are circulating, notably rhinoviruses.