Gut Microbiota and Probiotics in Influenza: A Narrative Review of Mechanisms and Emerging Evidence

The gut microbiota, often referred to as the "forgotten organ", plays an indispensable role in maintaining host physiological metabolism, immune function, and nutrient absorption. Moreover, the gut microbiome serves as a critical biological barrier against viral infections and is increasingly recognized as a potential target to augment antiviral therapies. Recent studies have revealed that microbial ligands and metabolites derived from the gut microbiota are pivotal in modulating respiratory immune responses, providing compelling evidence of the complex interaction network between microorganisms and the host, particularly the signaling pathways linking the gut to distal organs such as the lungs. This review examines the communication and regulatory mechanisms between the gut microbiota and pulmonary mucosal surfaces during influenza virus infection, emphasizing how gut microbial communities and probiotics influence host immune responses, promote the production of immune-related molecules, and enhance antiviral defenses. The aim is to provide comprehensive insights into the gut-lung axis and its implications for respiratory health.