Influenza From mid-November — Continuedthrough December 1993, influenza activity in the United States increased. This report summarizes surveillance information regarding influenza activity in the United States from October 3, 1993, through January 1, 1994. As of January 1, 1994, influenza viruses had been reported in 46 states; four states had not documented the presence of influenza this season (Delaware, Mississippi, New Hampshire, and Rhode Island). Nearly all (99%) influenza isolates reported to CDC have been influenza type A; one influenza type B virus was isolated in New York. Of the 750 influenza type A viruses reported from the World Health Organization (WHO) collaborating laboratories, 409 were subtyped as type A(H3N2) and 16 as type A(H1N1); 325 were not subtyped. As of January 10, 208 influenza isolates had been received by the WHO Collaborating Center for Influenza at CDC for antigenic analysis. Of the 68 influenza type A(H3N2) virus isolates completely analyzed, all were antigenically related to the A/Beijing/32/92(H3N2) strain included in the 1993–94 influenza vaccine. The ratio of specimens positive for influenza virus to total specimens submitted for respiratory virus testing increased from less than 0.01 in previous weeks t
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