The Changing Epidemiology of Respiratory Syncytial Virus and Influenza

Abstract

Influenza and respiratory syncytial virus (RSV) are the most important causes of medically attended acute respiratory illnesses. Medical encounters for acute respiratory illness peak each winter, coinciding with the peak of influenza activity. RSV is the most important cause of hospitalization of infants for acute lower respiratory illness. Surveillance of influenza and RSV have been maintained in Houston since 1974. Hospitalization rates during that period were compared with national data. U.S. influenza mortality rates and population dynamics were reviewed. The number of deaths attributed to influenza in the United States have increased from approximately 15,000 per year for the period from 1972 through 1984 to >50,000 from 1990 to 1999. RSV hospitalization rates for infants have more than doubled during the same period. Influenza epidemics have tended to occur earlier in Texas, with epidemic disease evident in early November in 3 of the last 4 years. Population dynamics with increased population density and urbanization probably are responsible for worsening of epidemics of the major respiratory viruses. New approaches to control will be necessary to reduce impact of these infections. These include earlier availability of influenza vaccine each autumn and use of antivirals and new vaccines for RSV.