Update: influenza activity--United States and worldwide, and composition of the 1992-93 influenza vaccine.

During the 11 influenza seasons from 1977 through 1988, more than 10,000 excess deaths attributed to pneumonia and influenza (P&I) were reported during each of seven seasons, and approximately 45,000 deaths were reported during each of two seasons (CDC, unpublished data, 1992). The most important strategy for preventing influenza-associated morbidity and mortality is vaccination of persons in high-risk groups with vaccine closely matched to circulating strains. In collaboration with state and local health departments, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza virus. This report summarizes surveillance for influenza in the United States and worldwide during the 1991-92 season and describes the composition of the 1992-93 influenza vaccine.