The risk of seasonal and pandemic influenza: prospects for control.

Seasonal influenza is an underappreciated cause of morbidity and mortality in the United States. Seasonal vaccination of individuals in groups at high risk of complications has long been recommended. However, there has been a gradual expansion of the recommended groups for annual influenza immunization in order to reduce the incidence of uncomplicated infection, to alleviate the impact of seasonal influenza on health care, and to simplify the application of recommendations. The threat of an influenza pandemic, heightened by recent cases of highly pathogenic avian influenza in humans, requires continued efforts in preparedness. Strategies for the control of pandemic influenza must include vaccines, antiviral drugs, and nonpharmaceutical interventions like school closure and voluntary quarantine around cases. The prophylactic efficacy of neuraminidase inhibitors, previously observed in household studies, suggests that they will be a useful adjunct to voluntary quarantine. Stockpiles of antiviral drugs are being established for therapeutic and perhaps preventive use for pandemic influenza.