Earlier, stronger: the wave affecting France no longer corresponds to pre-Covid benchmarks.
The bronchiolitis epidemic, which mainly affects infants, has reached the highest level of hospitalizations for more than ten years, announced this week Public Health France (SPF), in charge of its surveillance. The disease was the cause of half of the visits to the emergency room of children under 2 years old in the first week of November, and a third of the children who came for this reason were hospitalized in the process. The Minister of Health launched on Wednesday the national plan provided for in exceptional health situations (Orsan).
How to explain this wave which overwhelms many hospital pediatric services, already weakened by the hospital crisis? “Bronchiolitis this year was more severe from the outsetnotice the Pr Isabelle Claudet, head of the children’s department and pediatric emergencies at the Toulouse University Hospital. We currently have as many children in intensive care as at the ordinary peak of the epidemic, even though this peak is not expected, in our region, before the beginning of December.
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Maybe we should see the effect of traffic “concomitant and unusual” of several viruses causing bronchiolitis, reported by SPF. RSV (respiratory syncital virus), the main cause of bronchiolitis, is circulating earlier this year. This advance on the calendar makes it overlap with rhinoviruses (classic in this season) and metapneumoviruses, all of which can cause the same symptoms: inflammation of the walls of the bronchioles (the smallest bronchi), resulting in coughing and rapid, wheezing. The baby may have trouble feeding and breathing. Co-infections (simultaneous infections by two viruses) favored by this context are known to cause more severe cases.
Another hypothesis put forward is that of the “immune debt”, a concept devised by scientists during the Covid pandemic to explain the virulence of certain seasonal epidemics. The low circulation of viruses thanks to barrier measures (confinements, masks, ventilation, etc.) would have reduced the collective protection offered by regular exposure to these germs. Mahmoud Zureik, professor of public health at the University of Versailles Saint-Quentin-en-Yvelines, however, warns against hasty conclusions. “It is an attractive concept but which has not yet been scientifically demonstrated, we must let research continue on the subject. The risk is that people, the general public or decision-makers, deduce that it is not useful to protect themselves, since they will have to be contaminated sooner or later – to pay their debt, in a way. Assuming that the hypothesis is true, we can accumulate debts by avoiding ever catching the virus thanks to barrier gestures, and therefore, never pay said debts.
Pressure on hospitals
What about the evolution of the epidemic? “We observe a phenomenon of replacement of rhinoviruses, responsible for the first cases of bronchiolitis, by RSV which progresses, notes Bruno Lina, director of the reference center on influenza viruses in the southern region. This is not very good news: RSV causes more severe bronchiolitis in toddlers.
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The pressure on hospitals should therefore not ease immediately. Difficult, however, to make predictions, underlines the virologist. “The outbreak of Sars-Cov-2 has upset the known dynamics of other respiratory viruses.” Before the Covid-19 pandemic, bronchiolitis epidemics were very regular, with a peak reached around the 50e week of the year. But “it is now extremely complicated to model the evolution of the epidemic, it is very disturbing”, confirms Isabelle Claudet. It is therefore difficult to predict the volumes of visits to the emergency room, and the personnel required. His establishment has brought forward the annual recruitment campaign to August to strengthen the teams for winter epidemics. “But other hospitals are struggling, especially in areas where doctor and nurse positions are less attractive than before.”