Viral respiratory tract infections and asthma in early life: cause and effect?

Interactions between viral respiratory tract infections in infancy and childhood, and asthma development and exacerbation, are complex and intriguing. This review aims to unravel some of these complexities. Does severe respiratory viral infection early in life predispose to later asthma development, or is it indicative of a predisposition to allergic respiratory disease? How could variables such as age and severity of viral infection affect the interaction between respiratory viral infections and asthma? How could respiratory viral infection drive allergic sensitization? Here, we review the evidence surrounding these questions, and discuss current and future research and therapeutic approaches targeting the interplay between viral respiratory tract infection and asthma.