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Centers for Disease Control and Prevention

INFLUENZA SUMMARY UPDATE

(Week ending November 11, 2000-Week 45)

The following information may be quoted:

Synopsis: During week 45 (November 5-11, 2000), 23 of the specimens tested by WHO and NREVSS laboratories were positive for influenza type A virus and 2 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. Twenty state and territorial health departments reported sporadic influenza activity and 30 reported no influenza activity.

U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) Collaborating Laboratory Reports* : During week 45, WHO and NREVSS laboratories reported 631 specimens tested for influenza viruses, of which 25 (4 %) were positive. Twenty-one were influenza A (H1N1) viruses, 2 were unsubtyped influenza A viruses, and 2 were influenza B viruses.

Since October 1, WHO and NREVSS laboratories have tested a total of 5 562 specimens for influenza viruses, and 56 (1 %) have yielded influenza virus isolates. Of the 56 isolates identified, 49 (88 %) were influenza type A and 7 (12 %) were influenza type B.  Of the 49 influenza A viruses, 42 (86 %) have been subtyped; 40 (95 %) were A(H1N1) and 2 (5 %) were A(H3N2). Influenza A(H1N1) isolates have been identified in California, Florida, and Texas; influenza A (H3N2) isolates have been identified in Hawaii and Kentucky; and unsubtyped influenza A isolates have been identified in Florida, Louisiana, and Oklahoma. Influenza B isolates have been identified in Alaska, California, Florida, and Oklahoma.

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Pneumonia and Influenza (P&I) Mortality: During week 45, 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 7,7 % for week 45.

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Influenza Morbidity Reports from U.S. Sentinel Physicians*: During week 45, 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 sporadic in 20 states (Alabama, Alaska, Arkansas, Colorado, Florida, Georgia, Indiana, Kansas, Kentucky, Louisiana, Maine, Michigan, Nevada, New Mexico, Ohio, Tennessee, Texas, Utah, West Virginia, and Wyoming). Thirty 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 16, 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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