During viral infections, gut microbiota modulates the macrophage and neutrophil activity against respiratory viruses, such as SARS-CoV-2, and can improve respiratory defenses through the induction of granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling, thus promoting pathogen destruction and elimination by alveolar macrophages [74]. This evidence concerns the gene CSF2 and viral infectious disease.