Respiratory syncytial virus bronchiolitis : current and future strategies for treatment and prophylaxis.

Respiratory syncytial virus (RSV) is the most important cause of viral lower respiratory tract illness in infants and children worldwide and is responsible for over 120 000 annual hospitalizations in infants in the US alone. RSV is also recognized as a major respiratory viral pathogen in the elderly and other high-risk populations. Bronchiolitis, pneumonia, apnea, respiratory failure, and death are well known manifestations of severe acute RSV disease. RSV infection has also been associated with recurrent wheezing in children, but the mechanisms involved in this association are not completely understood. The host immune response plays a significant role in controlling the infection but is likely also involved in augmenting the disease through pathways that have not been completely identified. The treatment options for RSV infection are very limited. Ribavirin, corticosteroids, and bronchodilators are not used routinely because they have not proven to be sufficiently effective. Education of caregivers, strict handwashing, and avoidance of exposure to environmental factors associated with severe forms of RSV infection are among the most effective preventive means. Passive immunization with monoclonal antibodies provides protection against severe RSV disease in high-risk children. Clinical trials to evaluate the safety and efficacy of a second-generation monoclonal antibody are underway. Efforts to develop a safe and effective RSV vaccine have continued despite the poor outcomes observed following the administration of formalin-inactivated formulations in the 1960s. In the last decade, live attenuated vaccines (including those developed by recombinant techniques) and purified subunit vaccines have all been evaluated in humans. Results of clinical trials have been encouraging, but the availability of a safe and effective RSV vaccine is not a reality yet. Better prevention strategies will have an impact, not only on acute morbidity caused by RSV, but will also likely have an effect on ameliorating the chronic consequences of this disease.