Coronavirus disease 2019 (COVID-19) is caused by respiratory syndrome coronavirus qualified as SARS-CoV-2. Viral penetration requires binding of the viral spike (S) protein to a specific cellular receptor (ACE2) highly expressed in a nasal goblet and ciliated cells. In several countries, the COVID-19 evolution was relatively benign compared to others and despite noncompliance with health recommendations on several occasions. In this overview, we attempt to define the criteria that could explain such a difference. Among these criteria, the specificity of Lactobacillus genus strains, as a part of nasal microbiota, could play a role of a barrier against viral penetration and could strengthen the host's immune system in some populations rather than others. In fact, several studies have shown the role of lactic acid bacteria, including lactobacilli, in the prevention of viral respiratory infections. This could provide important information on a possible mechanism of the virus spreading.
Keywords: SARS-CoV-2; lactobacilli; nasal microbiota.
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