Control of common viral epidemics but not of SARS-CoV-2 through the application of hygiene and distancing measures.

BACKGROUND: We systematically survey respiratory and gastrointestinal infections of viral origin in samples sent to our university hospital institute in Marseille, southern France. Here, we evaluated whether the measures implemented to fight COVID-19 had an effect on the dynamics of viral respiratory or gastrointestinal infections. METHODS: We analysed PCR performed and positive for the diagnoses of viral respiratory and gastrointestinal infections over five years (January 2017-February 2021). Data were collected from our epidemiological surveillance system (MIDaS). Dates and contents of French measures against SARS-CoV-2 were collected from: https://www.gouvernement.fr/info-coronavirus/les-actions-du-gouvernement. RESULTS: Over the 2017-2021 period, 990,364 analyses were carried out for respiratory infections not including SARS-CoV-2, 510,671 for SARS-CoV-2 and 27,719 for gastrointestinal infections. During winter 2020-2021, when the most restrictive lockdown measures were in place in France, a marked decrease of infections with influenza viruses (one case versus 1,839-1,850 cases during 2017-2020 cold seasons) and with the RSV (56 cases versus 988-1,196 cases during 2017-2020 cold seasons) was observed, demonstrating the relative effectiveness of these measures on their occurrence. SARS-CoV-2 incidence seemed far less affected. Rhinoviruses, parainfluenza 3 virus, and the coronavirus NL63 remained at comparable levels. Also, the norovirus winter season positivity rates decreased continuously and significantly over time from 9.3% in 2017-2018 to 2.0% in 2020-2021. CONCLUSION: The measures taken to control COVID-19 were effective against lower respiratory tract infections viruses and gastroenteritis agents, but not on the agents of the common winter cold and SARS-CoV-2. This suggests that more specific measures to prevent COVID-19 and upper respiratory tract infections need to be discovered to limit the spread of this epidemic.