February 19, 1997

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

JAMA. 1997;277(7):528. doi:10.1001/jama.1997.03540310026016

INFLUENZA activity in the United States increased from mid-November through December 1996, peaked during December 22,1996-January 4,1997, and began to decline during January 5-18. Laboratory-confirmed influenza type A and/or type B has been reported in all states this season. This report summarizes influenza surveillance data from September 29,1996, through January 18, 1997.

As of January 18, World Health Organization collaborating laboratories in the United States had tested 20 754 specimens for respiratory viruses, and 4063 (20%) were positive for influenza. Of these isolates, 3959 (97%) were influenza type A, and 104 (3%) were influenza type B. The number of influenza isolates and percentage of specimens positive for influenza increased steadily during November and December. During the weeks ending December 28 and January 4, 31% of specimens tested were positive for influenza; however, the percentage positive for influenza declined to 25% during the week ending January