Introduction

Abstract

Respiratory syncytial virus (RSV) infection remains the most common reason for hospitalization of infants in the United States, and an important cause of mortality worldwide. The development of monoclonal antibodies against the fusion protein of RSV has provided the first means of protecting high-risk infants against severe forms of RSV infection. Many questions still remain concerning the optimal use of this preparation. Most important, the high cost of the product has limited its use primarily to those infants born at <32 weeks' gestation, with or without chronic lung disease of premature birth. Nevertheless, severe RSV disease occurs frequently in the group of infants born between 32 and 35 weeks' gestation, and the use of preventive measures in this group of infants deserves further scrutiny. The reports in this issue address this need in several ways. First, the clinical and social risk factors for severe outcomes of RSV infection are discussed including the potential mechanisms by which the presence of these factors actually translates into severe illness during RSV infection. Many of these mechanisms are present in infants born at 32 to 35 weeks' of gestation. Subsequent articles describe the degree to which RSV infection predominates as a cause of hospitalization in infancy, and illustrate how the 32- to 35-week gestational age group is perhaps the major consumer of resources such as intensive care and mechanically-assisted ventilation. Low birth weight irrespective of gestational age is identified as a predictor of increased morbidity after RSV infection. A preliminary but provocative analysis suggests that morbidity from RSV infection is not confined to the period of acute illness, but may be reflected in events occurring long after hospital discharge. Finally, the cost and benefit of RSV prophylaxis is compared with that of current measures for the prevention of varicella and pneumococcal infection. Readers of this issue will hopefully obtain further information concerning the epidemiology, pathogenesis, and economic impact of RSV infection. In addition, information in these articles may provide a new perspective for considering the use of preventive measures against RSV infection in the group of infants born at 32 to 35 weeks' gestation. The use of passive immunotherapy should not supplant instructing parents in various measures of reducing the frequency and severity of RSV infection. These measures include careful hand-washing, timing pregnancies so that infants will be several months of age before RSV epidemics occur, cessation of maternal smoking, and reducing the number of children to which the susceptible infant is exposed.