How the coronavirus stopped the flu epidemic

Social distancing and the closure of public places have shortened the seasonal flu epidemic, which ended precipitously in April. Other diseases such as chickenpox or measles have also seen their mortality plummet. The overall consequences on mortality will however be difficult to assess.

The seasonal flu causes between 290,000 and 650,000 deaths each year worldwide depending on the duration of the'epidemic and the effectiveness of vaccine. However, this year, the measures of confinement and social distancing brutally stopped the season, which could have saved hundreds of thousands of lives, estimates the World Health Organization which tracks cases of influenza via the FluNet network.

" Overall, influenza activity is lower than expected for this time of year. In the temperate zone ofnorthern hemisphere, a sharp drop in influenza activity has been observed in recent weeks Notes the organization. There has been a sharp drop in the number of cases from the last week of March, which coincides with the entry into force of the containment measures. The flu season has thus been shortened by 6 weeks compared to other years.

Local data confirms the trend. In Hong Kong, for example, the epidemic period of flu has been 63.2% shorter than the average of the last 5 years and the number of deaths has been reduced by 62.3%, says a study published in the BMJ May 4, when the season started on a date similar to that ofwinter previous (first week of January).

Barely 36 cases of rubella worldwide this year!

Other infectious diseases have been drastically reduced this year, says study co-author Pak-leung Ho and infectious disease researcher at the University of Hong Kong at the site Nature. The number of cases of varicella in Hong Kong fell by half, or even three-quarters, compared to previous years. In April, cases of measles and rubella were the lowest recorded since at least 2016: barely 36 cases of rubella had been counted worldwide in April, according to preliminary data. These diseases, which particularly affect children, were probably stopped by the closure of schools, judge Pak-leung Ho.

The 2020 flu promised to be particularly vigorous. In January, before the arrival of Covid-19, the epidemic had started on a high note, " on track to be one of the toughest in decades "Says Nature. But, with the brutal end of April, hundreds of thousands of lives could ultimately have been saved. Wearing masks, closing public places, seclusion … The measures put in place to combat the Covid-19 seem ironically to have had more effect on the flu than on this new one coronavirus himself, consider the study of BMJ. As the Sars-Cov, flu virus spreads via respiratory droplets.

Other factors, however, may have affected the statistics, says theWHO. It is, for example, likely that patients have seen less and gone to hospitals for fear of the coronavirus. According to data from Public Health France, the consultation rate for syndrome influenza is half as high this year as in 2019. Spring 2020 was also particularly hot in Europe, which weakens the virus. Finally, it is possible that elderly people who are normally dead from the flu have been taken away before by the coronavirus.

Will 2020 be more deadly than 2019?

This is in any case good news, when the flu season had already been exceptionally short in France in 2019, with only 8 weeks of epidemic. The overall excess mortality is however much higher in 2023. Between 1er March and May 15, 2020, we observe an excess mortality of 92.5% in Seine-Saint-Denis compared to the same period of 2019. The figure is 90.1% in the Haut-Rhin and 86.5% in the Hauts-de-Seine. But here again, let's not draw conclusions too quickly: " We could see a mortality deficit corresponding to the lives cut short by the epidemic, as it could be the case after the heat wave from 2003 ", Note INSEE. Likewise, the January 2017 peak of death from influenza was followed by low mortality points in March and April.

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