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January 8, 1997

Update: Influenza Activity— United States, 1996-97 Season

JAMA. 1997;277(2):105-106. doi:10.1001/jama.1997.03540260019010

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 activity in the United States from September 29 through December 7, 1996, and indicates that influenza activity has increased since mid-November.

From September 29 through December 7, a total of 602 (7%) of 8927 respiratory specimens tested by WHO collaborating laboratories in the United States were positive for influenza virus. Of the 602 positive cultures, 458 (76%) were reported during November 17-December 7. Of the 602 influenza isolates, 595 (99%) were influenza type A, and seven (1%) were type B. Of the 158 influenza type A isolates subtyped, all were A(H3N2). CDC further characterized 13 influenza A(H3N2) isolates, and all were antigenically similar to the H3N2 component of