The coronavirus is said to compete with seasonal flu. – BUFKENS CEDRIC / SIPA
- The seasonal flu epidemic is less virulent this year compared to the previous year.
- This could be explained by an increased effectiveness of vaccination.
- But also by competition with the Covid-19 which is rampant at present.
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Every winter, the flu is at the heart of concerns. It affects millions of people and causes several thousand victims in France. However, the virus is less virulent this year, with lower mortality than during last year’s flu epidemic.
Since November 2019, 72 people have died from the flu virus after being admitted to intensive care, according to figures recorded until March 4 by Public Health France, against 197 in the same period a year earlier. How to explain such a difference ? Is the seasonal flu vaccination? Strengthening barrier measures? Or the concurrent epidemic of
coronavirus? 20 minutes make the point.
More effective immunization and a smaller epidemic
This year, more French people wanted to protect themselves against the flu. Vaccination is on the rise this winter, with 600,000 more doses administered than last year. This increase could be explained in part by a novelty: for the first time, pharmacists had the right to vaccinate patients, thereby facilitating access to this mode of prevention.
So there have been more people vaccinated, but also a more effective vaccine than last year. “This year, the flu is not quite the same as that which circulated last year, explains Professor Bruno Lina, virologist, director of the National Reference Center for influenza for the south of France and researcher at
International Center for Infectious Disease Research (CIRI). Last year, the H1N1 and H3N2 strains were in circulation. This year, it is the H1N1 strains and a type B virus. And this difference explains why the vaccine efficacy is not the same: it is very difficult to vaccinate against the H3N2 strain, while it is easier to get developed an effective vaccine for a combination of H1N1 and type B virus ”.
In comparison, “the 2018-2019 flu epidemic was characterized by significant severity, despite its short duration, linked to the co-circulation of viruses A (H3N2) and A (H1N1) in a context of insufficient vaccination coverage and ‘Vaccination effectiveness variable according to the viruses (…) and marked by a significant excess mortality, with approximately 8,100 deaths attributed to influenza ”, confirms Public Health France.
In addition, “there is a” small epidemic “this year also because it appeared rather during school holidays, which slowed the spread of the virus, notes Dr. Jean-Louis Bensoussan, general practitioner and member of the MG France union. This explains why there have been far fewer cases in total, and why fewer elderly people – much more vulnerable to the flu – have contracted the virus, “he said.
Barrier measures more applied for fear of coronavirus
And what about the coronavirus? Did the arrival of Covid-19 in France upset the seasonal flu epidemic? “It had already started to decrease when the coronavirus arrived in France, answers Professor Bruno Lina. But the passage of the peak of the flu epidemic corresponds to the reinforcement of the barrier measures advocated to fight against the coronavirus – the same, moreover, than those against the flu, he specifies. One can legitimately think that this reinforcement, the increased vigilance of the population, which applies more these protective hygiene measures to keep the coronavirus at a distance, made it possible to slow down the spread of the influenza virus “.
Because the explosion of the number of cases of coronavirus on the territory pushed the French to rush on the bottles of gel hydroalcoholic, today in total shortage. And for lack of sufficient stocks of the precious disinfectant liquid, many people have adopted the reflex of washing their hands very regularly. “A very effective protective measure against the coronavirus and against the seasonal flu,” recalls Dr. Bensoussan. Hopefully people will keep these good habits in the future. “
Possible competition between the flu and the coronavirus
But could the arrival of Covid-19 in France have limited the spread of the flu virus? “Yes, confirms Professor Lina. Now that the coronavirus is implanted on the territory, there is competition between the two viruses. This is called viral interference: when two epidemic viruses circulate at the same time, on the same territory and target the same population, they oppose each other, and it is the virus with the most significant growth potential that takes over above ”, decrypts Professor Lina.
And as “the flu epidemic was already in its downward phase when the coronavirus arrived in France”, notes Dr. Bensoussan, “it is Covid-19 which has the most open field to spread”, completes the Pr Lina.
And if the two viruses are both characterized by flu-like symptoms, such as fever, cough, or even respiratory distress, they don’t have the same risks. “The seasonal flu affects children a lot, but kills many people in the elderly,” says the virologist. And this virus, which returns every year, has a mortality rate of around 0.2%. The Covid-19, it would reach a mortality rate of about 2%. But this rate could actually be much lower, considering that many people infected with Covid-19 develop few symptoms and are unaware that they have contracted it.
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