Recent trends in severe respiratory syncytial virus (RSV) among US infants, 1997 to 2000.

To provide current estimates of the incidence, associated risk factors, and costs of severe respiratory syncytial virus (RSV) infections among infants in the United States, defined as emergency department (ED) visits, hospitalization, and death. Retrospective analysis of National Hospital Ambulatory Medical Care Survey data 1997 to 2000; National Hospital Discharge Survey data 1997 to 2000; Perinatal Mortality Linked Files 1998 to 1999. The Hospital Cost Utilization Inpatient Sample data 1997 to 2000 were used to estimate hospitalization costs, and the 2001 Medicare fee schedule was used to estimate ED visit costs. Census data were used for population estimates. Between 1997 and 2000, there were 718,008 ED visits by infants with lower respiratory infection diagnoses during the RSV season (22.8/1000), and 29% were admitted. Costs of ED visits were approximately 202 million US dollars. RSV bronchiolitis was the leading cause of infant hospitalization annually. Total hospital charges for RSV-coded primary diagnoses during the 4 years were more than 2.6 billion US dollars. An estimated 390 RSV-associated postneonatal deaths occurred in 1999. Low birth weight and prematurity significantly increased RSV-associated mortality rates. RSV is a major cause of infant morbidity and mortality. Severe RSV is highest among infants of black mothers and Medicaid-insured infants. Prematurity and low birth weight significantly increase RSV mortality rates.