Update: influenza activity--United States and worldwide, 1993-94 season, and composition of the 1994-95 influenza vaccine.

In collaboration with the World Health Organization (WHO) and its network of international collaborating laboratories and with state and local health departments in the United States, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. This report summarizes surveillance for influenza in the United States and worldwide during the 1993-94 season and describes the composition of the 1994-95 influenza vaccine.