New research suggests that measures to prevent COVID-19 have reduced global flu cases and may have resulted in the disappearance of the B/Yamagata strain. The study highlights the impact of non-pharmaceutical interventions on virus evolution
During the COVID-19 pandemic, there was a dramatic decrease in seasonal flu cases worldwide following closures, travel restrictions and other social measures. But in areas where restrictions were less severe, such as South Asia and West Asia, the circulation cycle of certain influenza strains continued, and they even evolved in this environment. In particular, it seems that the B/Yamagata influenza strain has disappeared from surveillance since the beginning of the epidemic, and may be extinct.
In a new study, Chen and his colleagues from the American Association for the Advancement of Science (AAAS) examined the effect of non-pharmaceutical interventions (NPIs) implemented to control the corona virus, such as lockdowns, social distancing and mandatory mask wearing. They used epidemiological, genetic and international travel data from the period before, during, and after the pandemic, in order to examine the changes in the dynamics of the spread and evolution of influenza viruses.
The results showed that in areas where restrictions were less severe, such as South and West Asia, the spread of influenza A and B/Victoria strains continued. These trends highlight the impact of human interventions on the patterns of influenza and its evolution.
However, since the beginning of the pandemic, no additional cases of the B/Yamagata strain of influenza appear to have been recorded, suggesting the possibility that this strain is extinct. The researchers note that the non-pharmaceutical interventions were most effective in disrupting the spread of viruses and pathogenic diversity, and may even be more effective than vaccines alone.
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Why?
Very interesting, a very explosive topic, even after a few years.
It seems to me, on the contrary, that closures caused more seasonal flu morbidity due to the weakening of the immune system because we were closed and did not "train" for viruses.