Bronchiolitis: An Overview of the Disease

Bronchiolitis is an epidemic respiratory illness caused primarily by the respiratory syncytial virus (RSV). It mainly affects children under the age of 2. In the vast majority of cases, bronchiolitis is mild and resolves on its own. The most common symptom of bronchiolitis is nasal congestion (mild cough, moderate fever).

Bronchiolitis is highly contagious and spreads through saliva, sneezing, coughing, hands, and contaminated objects (toys, pacifiers, “security blankets”). Thus, a cold in a child or adult can cause bronchiolitis in an infant.

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Winter 2020–2021: a much lower incidence than in previous seasons

The bronchiolitis outbreak began in week 05/2021, peaked in week 13/2021, and ended in week 23/2021. It lasted 15 weeks, comparable to the previous season, though the outbreak occurred later in the year, with the peak occurring 13 weeks later than in the 2019-2020 season.

Key points in mainland France

• 6.4% of all emergency department visits among children under 2 years of age were due to bronchiolitis—a sharp decline compared to previous seasons.

• Among children seen in the emergency room for bronchiolitis, 38.9% were hospitalized—a proportion comparable to previous seasons.

• Among medical procedures performed by SOS Médecins on children under 2 years of age, 4.1% were related to bronchiolitis—a downward trend compared to previous seasons.

• RSV continued to circulate during July 2021 in certain metropolitan regions.

Key Points in the Overseas Territories

• Antilles: Epidemic thresholds were never exceeded.

• Mayotte: The outbreak began in week 17, and the peak was reached in week 24. See the latest epidemiological update on bronchiolitis in Mayotte.

• Réunion: The epidemic, which began in week 17, has been declining since week 23 and ended in week 29. See the latest epidemiological update on bronchiolitis in Réunion.