Factors predicting childhood respiratory syncytial virus severity: what they indicate about pathogenesis

A plethora of clinical experience exists defining the factors associated with differences in severity of childhood respiratory syncytial virus (RSV) infections. These clinical severity factors reveal a wealth of information about the pathogenesis of this disease. Reviewing and interpreting the clinical risk factors to gain an insight into RSV pathogenesis is important, especially considering the relative lack of parallel between many animal models of RSV infection and observed human disease.

Existing and unpublished data on severity risk factors are reviewed and placed into a working pathogenesis model.

Important factors discussed are: (1) the critical role of the timing of the infection; (2) its rapidity of progression to involve the lower respiratory tract; (3) factors limiting this spread; (4) the nature of the pathogenic immune response; and (5) the host genetic and other factors that alter this immune response.

Pending new data involving these and other processes will more fully illuminate the spectrum of childhood RSV disease.