While the coronavirus circulates less and the bronchiolitis epidemic decreases, remaining at a high level, the spread of the flu is accelerating everywhere in France at the end of 2022. The Minister of Health, François Braun, mentioned, on Wednesday, December 28 , “a week of all dangers”. “There is an explosion of cases [de grippe]with also serious cases, which makes resuscitation services globally saturated”said the former ER doctor. In fact, hospitalizations for flu-like illnesses have increased by 75%, Public Health France (SPF) said in its latest epidemiological bulletin.
Several indicators show the earliness of the flu this season. According to data from the Sentinelles network, which brings together more than 1,300 liberal general practitioners, the rate of consultations for flu symptoms was estimated at 460 per 100,000 inhabitants for the penultimate week of 2022. This figure is very high for this period. of the year, compared to those of the last ten years, when the peak of the epidemic generally occurred between February and March.
The proportion of flu-like illnesses among SOS-Doctors consultations also provides information on the scale of the epidemic. For eight weeks in a row, these inquiries have been on the rise and are earlier than in previous years.
The proportion of hospitalizations due to influenza is the highest since 2010
Hospital data also shows that the epidemic is accelerating. Across all age groups, the number of ER visits for influenza continued to increase (+52% over week 50), as did the number of hospitalizations after an ER visit for influenza (+75% in one week). . ).
The health authorities indicate that, the week of December 19, the proportion of hospitalizations due to influenza or influenza-like illness reached 41.2 per 1,000 hospitalizations for all causes combined, that is, the “highest value observed for this indicator during the period 2010-2023” in the same week of the year.
Since October 3, at least 193 severe cases of influenza have been admitted to intensive care, including 142 since December 5. Among them we found mostly older people (80 were 65 years of age or older), but also younger: 16 were between 0 and 4 years old, 16 between 5 and 14 years old, and 79 between 15 and 64 years old, according to the SPF weekly bulletin, which specifies that these data are based on about forty intensive care units and are not exhaustive.
A growing positivity rate
Like the SPF shade, certain indicators taken into account in influenza surveillance are based on patients’ symptoms, which tends to skew data during the Covid-19 pandemic. “Therefore, it is likely that some of the cases of influenza-like illness reported by our influenza surveillance are due to Covid-19 and not influenza.”says the organization.
“This is the ambiguity of the expression “flu syndrome”, which can be related to various diseasescomments Vincent Enouf, deputy director of the National Reference Center for Respiratory Infectious Viruses at the Institut Pasteur. Therefore, we must look next to the tests, whose positivity rate for the flu has increased in recent weeks. » In city medicine, the Sentinels network reported a positivity rate of 65.3% in week 51, up from 56% the week before. In hospitals, the positivity rate was 20.1%, up from 13.9% two weeks earlier.
“In the past, epidemics where H3N2 was the majority were stronger, more virulent and caused more deaths”
“We are facing the first flu epidemic in at least a decade.comments Sibylle Bernard-Stoecklin, an epidemiologist in SPF’s department of infectious diseases. It arrived two weeks earlier than in 2017-2018, which was already one of the first. » This specificity is observed in other parts of Europe, in North America, but also in Australia and New Zealand this summer, while last season’s epidemic was, on the contrary, very late: it had started in March. The epidemiologist, however, specifies that “The time of year when an influenza epidemic occurs is not necessarily related to its severity”.
Difficult to predict the peak or duration of theepidemic
Vincent Enouf shares this observation: “What will tell us if it is a great epidemic is the majority virus. » In metropolitan France, subtype A (H3N2) continues to be the most prevalent, although an increase in the detection of type B virus (Victoria) has been observed for several weeks. “A (H3N2) is a virus that evolves faster than others, adapts better and has a greater ability to escape the vaccineexplains the Institut Pasteur researcher. When we look back, the epidemics where A (H3N2) predominated were stronger, more virulent and caused more deaths, especially among people at risk, in terms of the [coronavirus] SARS-CoV-2. »
“However, it is not because the A (H3N2) virus is in the majority at the beginning of the epidemic that it will remain so throughout the season.specifies Sibylle Bernard-Stoecklin. This is, in particular, why it remains very difficult to predict the peak of the epidemic or how long it will last: there may be a rebound carried by another virus. »
The flu causes between 10,000 and 15,000 deaths each year, according to the Institut Pasteur, the health authorities point to the” emergency “ vaccinate people at risk and remember the importance of barrier gestures, especially during the end of the year celebrations. In 2021-2022, only 56.8% of people over the age of 65 got a flu shot. For this season the figures are not yet known.
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