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Current Trends Update: Influenza Activity -- United States

Reports of influenza activity from family physicians, state health departments, and collaborating diagnostic laboratories indicate that U.S. influenza activity is at elevated but declining levels.

Reports of influenza-like cases from the practices of sentinel physicians* for the week ending February 26 averaged 10.4, a decrease from the average of 11.2 reported for the preceding week (Figure 3). Outbreaks of influenza-like illness were reported by 14 states and the District of Columbia for the week ending March 8, a decrease from the 25 states that reported outbreaks the preceding week. Seven states indicated widespread outbreaks; seven states and the District of Columbia indicated regional outbreaks.

Isolates of type B influenza virus have now been reported from every state, and type A(H3N2) influenza viruses, from 31 states during the 1985-1986 influenza season. Incomplete totals for the week ending March 1 include 130 type B and 35 type A(H3N2) isolates; 187 type B and 47 type A(H3N2) viruses were reported for the week ending February 22. Overall, 1,714 influenza virus isolates, including 78.5% type B viruses and 21.5% type A(H3N2) viruses have been reported this season.

The percentage of pneumonia and influenza (P&I) deaths reported from the 121 U.S. cities for the week ending March 8 was 6.1%, compared with 6.3% for the preceding week. This is the ninth consecutive week that the P&I percentage has exceeded the statistical limit expected in the absence of influenza outbreaks nationwide. Reported by State and Territorial Epidemiologists; State Laboratory Directors; Statistical Svcs Br, Div of Surveillance and Epidemiologic Studies, Div of Field Svcs, Epidemiology Program Office, WHO Collaborating Center for Influenza, Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC. *Cases reported by those members of the American Academy of Family Physicians research panel who serve as sentinel physicians for influenza.

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