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Influenza Summary Update

(Week ending December 9, 2000-Week 49)

The following information may be quoted:

Synopsis: During week 49 (December 3-9, 2000), 39 of the specimens tested by WHO and NREVSS laboratories were positive for influenza type A virus and 12 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 7.2%.  This percentage is below the epidemic threshold for this time of year.  Five state and territorial health departments reported regional influenza activity, 31 reported sporadic activity, and 13 reported no influenza activity.  

U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) Collaborating Laboratory Reports

During week 49, WHO and NREVSS laboratories reported 870 specimens tested for influenza viruses, of which 51 (6%) were positive.  Thirty-three were influenza A (H1N1) viruses, 6 were unsubtyped influenza A viruses, and 12 were influenza B viruses.

Since October 1, WHO and NREVSS laboratories have tested a total of 11,744 specimens for influenza viruses, and 245 (2%) have yielded influenza virus isolates.  Of the 245 isolates identified, 182 (74%) were influenza type A and 63 (26%) were influenza type B.  Of the 182 influenza A viruses, 145 (80%) have been subtyped; 138 (95%) were A (H1N1) and 7 (5%) were A (H3N2).  Influenza A (H1N1) isolates have been identified in California, Colorado, Florida, Indiana, Massachusetts, North Carolina, Oklahoma, Pennsylvania, South Dakota, Texas, and Wisconsin; influenza A (H3N2) isolates have been identified in Florida, Hawaii, Kentucky, and Missouri; and unsubtyped influenza A isolates have been identified in California, Florida, Georgia, Indiana, Louisiana, Missouri, New York, North Dakota, Oklahoma, Texas, and West Virginia.   Influenza B isolates have been identified in Alaska, California, Florida, Louisiana, Missouri, North Carolina, Oklahoma, Oregon, South Carolina, and Texas.


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Antigenic Characterization of Viral Isolates:  CDC has antigenically characterized 22 influenza viruses received from U.S. laboratories since October 1: 1 influenza A (H3N2) virus, 19 influenza A (H1N1) viruses, and 2 influenza B viruses.  These viruses are 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 49, the percentage of all deaths due to P&I as reported by the vital statistics offices of 122 U.S. cities was 7.2%.  This percentage is below the epidemic threshold of 8.1% for week 49. 

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Influenza Morbidity Reports from U.S. Sentinel Physicians *: During week 49, 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.   

Bar Chart for Influenza-like Illness(3368 bytes)

 Influenza Activity as Assessed by State and Territorial Epidemiologists**: Influenza activity was reported as regional in 5 states (Georgia, Hawaii, Kentucky, Tennessee, and Texas) and sporadic in 31 states (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Florida, Illinois, Indiana, Iowa, Kansas, Louisiana, Maine, Michigan, Mississippi, Missouri, Nevada, New Mexico, North Carolina, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Utah, Virginia, Washington, West Virginia, Wisconsin, and Wyoming).  Thirteen states reported no influenza activity and 1 state did not report.

Usmap for Weekly Influenza Activity (8735 bytes)

* 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: December 14, 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

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