Why is the bronchiolitis epidemic so strong this year?

For two and a half years, the Covid-19 pandemic has disrupted the classic seasonal cycle of other respiratory epidemics. Bronchiolitis, which usually starts in mid-November, peaks in December and dies out in January, was up 6 weeks earlier this year and is already higher than a decade ago, with about seven thousand emergency room visits. Last week of October.

If the indicators fell on Wednesday, November 16 in the bulletin, Public Health France (SPF) calls for caution: it could be a phenomenon after the school holidays and “It is likely that we will see a recovery this week, which will be reflected in next week’s epidemiological bulletin”– adds Sophie Vox, from the Infectious Diseases Department of the SPF. To explain this unusual dynamic, many pediatricians have put forward the concept “immune debt”At the forefront of lively debate among scientists.

The concept entered the public debate with a text published by French pediatricians Infectious diseases now in August 2021. According to these doctors, the barrier gestures associated with Covid-19 have limited the circulation of respiratory viruses and led to “Lack of immune stimulation” Population. This phenomenon, with the low volume of childhood vaccinations, “It caused immune debt which may have negative consequences when the pandemic is under control.”. Put more simply: since 2020, fewer people have been infected with respiratory viruses that cause bronchiolitis, such as respiratory syncytial virus (RSV) or rhinoviruses; Consequently, the population that will catch them in 2022 is larger than usual, which partly explains the levels observed today.

“reverse effect”

This hypothesis about the low immunization of the population against RSV “It’s interesting to watch”emphasizes Sophie Vaks, who prefers to talk“rebound effect” Coincides with the lifting of measures against Covid-19. If there is a debt, it in no way applies to newborns who simply have never encountered these viruses. That’s why Francois Angulvant, head of the pediatric department at the Hospital Université Vaudois Center in Switzerland and co-author of the article. Infectious diseases nowhighlights the population dimension of this debt. “Immune debt is not owed to hospitalized children, but to their parents. The more RSV circulating among them, the more contamination there will be., claims the pediatrician. Since RSV causes a simple cold in most adults, they are not necessarily aware of contaminating a younger person.