Update: influenza activity--United States, 1997-98 season

In collaboration with the World Health Organization (WHO), its collaborating laboratories, and state and local health departments, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. This report summarizes influenza surveillance in the United States from September 1 through December 12, 1997, which indicates that influenza activity is at typical levels for this time of year and that influenza A(H3N2) viruses have been most commonly isolated.