It is also known that respiratory virus infection causes perturbations in the gut microbiota. Diet, environmental factors and genetics play an important role in shaping gut microbiota which can influence immunity [164]. There is growing evidence that supports the roles of the gut microbiota and diet to shape immunity [165]. Modulating the composition and metabolic capacity of the microbiome for specific dietary components is a promising strategy for influencing immune responses against VRIs. Functional food components including probiotics, prebiotics and other bioactive ingredients of plant origin have been associated with immune benefits, mainly via microbiota modulation and impact on oxidative stress [65].