Update: influenza activity--worldwide, 1990-91, and influenza vaccination--United States.

During the 1990-91 influenza season, influenza occurred at relatively low levels throughout much of the world. All reporting countries (except Brazil and Papua New Guinea, which reported epidemic levels) indicated either sporadic cases, small local outbreaks, or regional outbreaks. This report summarizes worldwide influenza activity reported from April through September 1991.