The coronavirus epidemic raging in France should not make us forget another disease that has already killed 72 people in the country since the start of winter: seasonal flu. The most fragile subjects, generally very young children or the elderly, often face more or less serious complications, which can bring them to the hospital. However, a study carried out jointly by researchers from the Lille Center for Infection and Immunity and the National Institute for Agronomic Research, maintains that it would be possible to fight against bacterial secondary infections caused by influenza thanks to the microbiota , that is to say the microorganisms naturally present in our digestive system.
What are the main complications from the flu?
The most frequent complications are respiratory decompensations in patients suffering from chronic obstructive pulmonary disease or asthma or pneumonia due to a secondary bacterial infection.
How can the microbiota act on these complications?
When you have the flu, you eat less spontaneously. This reduction in food transiently modifies the composition and metabolic activity of the intestinal microbiota.
In addition, during the flu, the production of short-chain fatty acids by microbiota bacteria is also reduced. However, according to this study, these fatty acids promote the bactericidal activity of macrophages present in the lungs from a distance. The disruption of the intestinal microbiota by influenza therefore compromises the pulmonary defenses, in particular against Streptococcus pneumoniae, the primary cause of bacterial pneumonia in humans.
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How can we change the composition of the microbiota to allow it to better fight the complications of influenza?
Researchers have shown that this sensitivity to secondary bacterial infection can be corrected by treatment with acetate, one of the main short-chain fatty acids produced by the microbiota. Ultimately, it would be possible to avoid the serious complications of the flu.
Beyond the complications, there is an effective means of prevention against influenza: vaccination. Vaccination decreases morbidity in healthy adults by about 80%. It is a little less effective in the elderly, but still lowers mortality by 70 to 80% in this fragile population. The variability of the virus implies an annual renewal of the vaccination. However, flu vaccination coverage remains rather low. It was 51% among people over 65 in 2018, and would only be 7% among pregnant women.