While health authorities fear the saturation of hospitals, put under pressure by winter viruses and shortages of caregivers, the epidemiologist Antoine Flahault director of the Institute of Global Health in Geneva (Switzerland), gives keys to guard against the Christmas flu.
Why is the flu epidemic earlier this year and possibly more severe, like in the United States?
During the last twenty years, half of the flu epidemics started before Christmas and the other half after the holidays. Its early arrival this fall is therefore not exceptional. The extent of epidemics also varies: some winters, only 1 to 3% of the population is affected; sometimes it goes up to 5 or 10%. Will the flu be more severe this year? It’s still too early to tell, but that seems to be the case in the United States, where the epidemic is a bit ahead of ours. A clue: H3N2, the dominant strain in Europe this season, as across the Atlantic, is characterized by greater virulence in the elderly.
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New hospitalizations have more than doubled in a week according to Public Health France, and the Ile-de-France regional health agency launched a call on Friday for the mobilization of liberal health professionals to help hospitals. Could the circulation of influenza viruses lead to saturation of health establishments in the coming weeks?
As the epidemic was very moderate last year and almost non-existent in 2020, the pool of people likely to catch the virus has increased a little. The circulation of bronchiolitis viruses, Covid and influenza is currently intense and coincides, this year, increasing hospital tension. The main risk, with the flu, is a significant excess of mortality among the elderly. Even if white plans are regularly triggered in winter as the epidemic peak approaches and even if the situation can become tense during these holidays or in January, the phenomenon of excess mortality, which appears in the statistics after the fact, is sometimes difficult to perceive in real time. Because the flu rocks frail, elderly and sick people. And death certificates don’t always list it as the cause of death.
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Half of flu cases occur in people under 20
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The flu is almost as old as human beings. Are we doing enough to guard against this well-known threat?
We did it once in human history: during the first two years of the pandemic! In 2020 and 2021, we had almost no flu epidemic. It was a real miracle that went unnoticed: it is therefore possible to counter these respiratory viruses. The flu is much less contagious than the Covid: the R, its reproduction rate, that is to say the number of people infected by a patient, is indeed 1.5. This is enough to trigger strong epidemics but it is much less than the R of the Covid. The current sub-variants of Omicron have an R greater than 10. There is even talk of an R of 16 in China today! However, to stop an epidemic, this figure must be brought down below 1. With the flu, the path to go from 1.5 to 1 is much shorter than with the Covid. To do this, three prevention strategies must be combined: convince the over 65s and other people at risk of severe forms (immunocompromised, pregnant women, etc.) to get vaccinated; better ventilate enclosed spaces; wear the mask in transport and all closed and poorly ventilated places. Individually too, the flu is not inevitable, and a fortiori at Christmas! Grandparents can avoid being contaminated by a sick grandchild by isolating them in a room, putting on a mask and ventilating their home well. It is promiscuity in a poorly ventilated room that is risky.
The government has not reinstated the wearing of compulsory masks despite the triple epidemic of bronchiolitis-Covid-flu. Do you understand it?
I have long been reluctant to comment, as a scientist, on the question of the obligation concerning the mask, thinking that it was the sole responsibility of politicians, but it is becoming clear that the recommendations and other calls for individual responsibility made by the political and health authorities have failed in this area . Several North American scientific publications have also shown that the obligation to wear a mask was much more effective in reducing the risk of Covid than the simple recommendation. The population is expressing signs of pandemic fatigue after almost three years of Covid and, without the obligation, it is likely that it will not be put back. I now wear an FFP2 mask in the train because the surgical mask is only effective if everyone or almost everyone wears it in the car. This more filtering model is the most relevant today to protect those who wish to be protected.
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How to distinguish influenza from other respiratory viruses?
It is not easy because the symptoms of the flu and the Covid are similar: fever, sore throat, cough, asthenia, etc. Drug tests cannot fully resolve the dilemma as antigenic Covid tests are less sensitive with Omicron. You can be falsely negative after a sample in a pharmacy or after a self-test at home. As for the flu, tests are generally not done in practice, except in hospitals or as part of research or health monitoring protocols.
Flu vaccines have a bad reputation, and the target of 75% of risk groups set by the High Authority for Health has never been reached (56% in 2020-2021). Is their effectiveness in question?
It all depends on what we’re talking about. As the influenza virus mutates frequently, the composition of vaccines must be adapted each year, and their effectiveness in real life is not known until after the start of the winter epidemic. In general, their effectiveness against clinical forms of the disease is variable, from 40 to 70%, but not 100%. Hence their bad reputation in the population. On the other hand, influenza vaccines are very effective in preventing severe forms, those that cause death.
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There was a form of laziness of the pharmaceutical laboratories
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Given their contribution to the transmission of influenza and to avoid pediatric hospitalizations, the WHO as well as several European and North American countries recommend influenza vaccination in children and even infants. What do you think ?
Half of the cases of influenza occur in people under the age of twenty. Although the effectiveness of influenza vaccines is not perfect, it is better in children. Vaccinating them would therefore be interesting from an epidemiological point of view. For the health of children and teenagers, to reduce absenteeism at school and also to protect families, especially the elderly, as has been demonstrated for a long time in Japan. But French pediatricians seem rather reluctant to this prospect…
Why is this question not publicly debated in France?
The main reason for the poor image of flu vaccines seems to me to be their average performance. There has been a form of laziness on the part of pharmaceutical companies, which are reaping juicy gains but devoting little effort to innovation in this area. However, as the Covid has shown, when you want to innovate, you can! Pharmaceutical companies have been sitting on a situational annuity for years, thanks to seasonal campaigns for the elderly, without investing to find more effective vaccines against influenza, that is to say closer to 100% on clinical forms.