It is an unprecedented winter. Influenza virus, rhinovirus and respiratory syncytial virus (RSV), responsible for most cases of bronchiolitis… For the first time since the start of the Covid-19 pandemic in France, in March 2020, several other respiratory viruses are circulating at the same time as SARS-CoV-2, at very high levels. The lifting of restrictive measures, such as confinements or the compulsory wearing of masks, gives the usual seasonal viruses the opportunity to spread.
Across the Atlantic, this intensive co-circulation has been popularized under the term “triplemic”a triple epidemic that threatens to overwhelm – in the United States too – a health system already very weakened by the pandemic and a structural hospital crisis. “The particular challenge for this year is to study the interaction of SARS-CoV-2 with other viruses”underlines Anne-Claude Crémieux, professor of infectiology at the Saint-Louis hospital, in Paris, and author of the Citizens have the right to know (Fayard, 324 pages, 20 euros).
The bronchiolitis epidemic, which particularly affects children under 2 years of age, began early in October, whereas it usually adopts a very regular cycle, with an onset in mid-November, a peak in December and end in January. After a decrease linked to the school holidays, visits to the emergency room and hospitalizations have started to rise again since the week of November 14 and have reached levels not seen for ten years. At the origin of this infection of the bronchioles, the RSV and the rhinovirus share the metropolitan territory, one or the other imposing itself differently according to the regions.
It’s an early start also for influenza, known to have greater variability in the onset and magnitude of its seasonal epidemic. After Brittany, four other regions have entered the pre-epidemic phase, according to the bulletin of Public Health France (SPF) of November 23. The currently predominant subtype is the A(H3N2) virus. “Who says H3N2 says a fairly strong epidemic, which mainly affects people at riskunderlines Vincent Enouf, deputy head of the national reference center for respiratory infection viruses at the Institut Pasteur. Every year, influenza epidemics cause 8,000 to 10,000 deaths, figures which risk being exceeded if the majority strain remains the H3N2 flu. » This virus is not necessarily more dangerous than the others, but it evolves a lot genetically, which makes it more difficult to acquire long-lasting immune protection.
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