Early Life Microbiota and Respiratory Tract Infections.

Over the last decade, it has become clear that respiratory and intestinal tract microbiota are related to pathogenesis of respiratory tract infections (RTIs). Host and environmental factors can drive respiratory microbiota maturation in early life, which in turn is related to consecutive susceptibility to RTIs. Moreover, during RTIs, including viral bronchiolitis, the local microbiome appears to play an immunomodulatory role through complex interactions, though causality has not yet been fully demonstrated. The microbiota is subsequently associated with recovery after RTIs and can be related to persistent or long-term sequelae. In this Review, we explore the epidemiological evidence supporting these associations and link to mechanistic insights. The long-term consequences of childhood RTIs and the comprehensive role of the microbiota at various stages in RTI pathogenesis call for early life preventative and therapeutic interventions to promote respiratory health.