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Update: Influenza Activity -- United States

Influenza isolates reported to CDC this season have increased from 707 two weeks ago (1) to 971 (Figure 2). Seventeen states now report influenza type A(H1N1) virus activity, although most isolates (91%) continue to be identified as type A(H3N2) related to the A/Bangkok/79 component of the current vaccine. Influenza type A(H3N2) virus isolates have been reported from 42 states. An influenza B isolate was recently reported from Minnesota, raising to seven the number of states with influenza B activity.

Influenza morbidity reports collected weekly from each state suggest a gradual decline in activity. Since the week ending February 19, states reporting regional activity have decreased from 15 to seven, coincident with an increase in states reporting sporadic activity, 21 to 33. For the week ending March 19, 1983, four states (Iowa, Kentucky, Nebraska, and Virginia) reported widespread activity. For that same week, an excess in the ratio of pneumonia and influenza (P&I) deaths to total deaths was reported from 121 cities for the 10th consecutive week (Figure 2). The observed ratio was 5.1, and the expected ratio was 4.1. Reported by Respective state epidemiologists and laboratory directors; Div of Surveillance and Epidemiologic Studies, Epidemiology Program Office, WHO Collaborating Center for Influenza, Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.


  1. CDC. Update: influenza activity--United States. MMWR 1983;32:120-1.

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