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Centers for Disease Control and Prevention

Influenza Summary Update

(Week ending November 25, 2000-Week 47)

The following information may be quoted:

Synopsis: During week 47 (November 19-25, 2000), 26 of the specimens tested by WHO and NREVSS laboratories were positive for influenza type A virus and 3 were positive for influenza type B virus.   The proportion of patient visits to sentinel physicians for influenza-like illness was within baseline levels of 0 % to 3 % in the United States overall and in all 9 surveillance regions.  The proportion of deaths attributed to pneumonia and influenza was 6,5 %.   This percentage is below the epidemic threshold for this time of year.  Two state and territorial health departments reported regional influenza activity, 24 reported sporadic activity, and 24 reported no influenza activity.  

U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) Collaborating Laboratory Reports*: During week 47, WHO and NREVSS laboratories reported 694 specimens tested for influenza viruses, of which 29 (4 %) were positive.  Nineteen were influenza A(H1N1) viruses, 2 were influenza A(H3N2) viruses, 5 were unsubtyped influenza A viruses, and 3 were influenza B viruses.

Since October 1, WHO and NREVSS laboratories have tested a total of 8 511 specimens for influenza viruses, and 118 (1 %) have yielded influenza virus isolates.  Of the 118 isolates identified, 101 (86 %) were influenza type A and 17 (14 %) were influenza type B.  Of the 101 influenza A viruses, 86 (85 %) have been subtyped; 79 (92 %) were A(H1N1) and 7 (8 %) were A(H3N2).   Influenza A(H1N1) isolates have been identified in California, Colorado, Florida, Oklahoma, and Texas; influenza A(H3N2) isolates have been identified in Florida, Hawaii, Kentucky, and Missouri; and unsubtyped influenza A isolates have been identified in Florida, Louisiana, Missouri, and Texas.  Influenza B isolates have been identified in Alaska, California, Florida, Missouri, North Carolina, and Oklahoma.

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Antigenic Characterization of Viral Isolates:  CDC has antigenically characterized 4 influenza viruses received from U.S. laboratories since October 1: 1 influenza A(H3N2) virus, 2 influenza A(H1N1) viruses, and 1 influenza B virus.  The viruses were antigenically similar to vaccine strains A/Panama/2007/99 (H3N2), A/New Caledonia/20/99 (H1N1), and B/Beijing/184/93, respectively.


Pneumonia and Influenza (P&I) Mortality: During week 47, the percentage of all deaths due to P&I as reported by the vital statistics offices of 122 U.S. cities was 6,5 %.  This percentage is below the epidemic threshold of 7,9 % for week 47. 


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Influenza Morbidity Reports from U.S. Sentinel Physicians*: During week 47, 1 % of patient visits to U.S. sentinel physicians were due to influenza-like illness (ILI).  The percentage of ILI was within baseline levels of 0 % to 3 % in all 9 surveillance regions.

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Influenza Activity as Assessed by State and Territorial Epidemiologists**: Influenza activity was reported as regional in 2 states (Kentucky and Texas) and sporadic in 24 states (Alabama, Alaska, California, Colorado, Florida, Georgia, Hawaii, Indiana, Kansas, Louisiana, Maine, Michigan, Missouri, New Mexico, New York, Nevada, North Carolina, Ohio, Oklahoma, Oregon, Tennessee, Utah, West Virginia, and Wyoming).  Twenty-four states reported no influenza activity.
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* Reporting is incomplete for this week. Numbers may change as more reports are received.

** Influenza activity is defined as influenza-like illness and/or culture-confirmed influenza.

 Report prepared: November 30, 2000               

Appendix I: Regions

New England:           Connecticut, Maine, Massachusetts, New Hampshire, Vermont, Rhode Island
Mid-Atlantic:              New Jersey, New York City, Pennsylvania, Upstate New York
East North Central:   Illinois, Indiana, Michigan, Ohio, Wisconsin
West North Central:  Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota
South Atlantic:           Delaware, Florida, Georgia, Maryland, North Carolina, South Carolina,
                                    Virginia, Washington, D.C., West Virginia
East South Central:  Alabama, Kentucky, Mississippi, Tennessee
West South Central: Arkansas, Louisiana, Oklahoma, Texas
Mountain:                   Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, Wyoming
Pacific:                       Alaska, California, Hawaii, Oregon, Washington


National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, GA

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