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Centers for Disease Control and Prevention

INFLUENZA SUMMARY UPDATE

(Week ending November 4, 2000-Week 44)

The following information may be quoted:

Synopsis: During week 44 (October 29- November 4, 2000), two of the specimens tested by WHO and NREVSS laboratories were positive for influenza type A 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 6,3 %. 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 44, WHO and NREVSS laboratories reported 606 specimens tested for influenza viruses. Two influenza A isolates were identified: one A(H1N1) and one A(H3N2).

Since October 1, WHO and NREVSS laboratories have tested a total of 4 066 specimens for influenza viruses, and 17 were positive. Of the positive results, 14 were influenza type A and 3 were influenza type B. Of the 14 influenza A viruses, 13 have been subtyped; 11 were A(H1N1) and 2 were A(H3N2).

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Pneumonia and Influenza (P&I) Mortality: During week 44, the percentage of all deaths due to P&I as reported by the vital statistics offices of 122 U.S. cities was 6,3 %. This percentage is below the epidemic threshold of 7,6 % for week 44.

Prior to the 1999-2000 season, a new case definition for a P&I death was introduced in the 122 Cities Mortality Reporting System. It was recognized that one potential effect of using this case definition was to increase P&I mortality measurement levels in comparison to previous seasons. During the summer of 2000, the P&I mortality data were analyzed to determine if the modified case definition had affected mortality estimates. On the basis of this analysis, we estimate that there was an approximately 0,8 % upward shift in 1999-2000 mortality estimates. The 0,8 % shift did not represent a true increase in mortality. To adjust for this upward shift in mortality estimates, the 122 cities P&I mortality baseline and epidemic threshold for the 2000-01 season have been adjusted upward as well.

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Influenza Morbidity Reports from U.S. Sentinel Physicians*: During week 44, 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 (Alaska, Arkansas, Colorado, Florida, Georgia, Hawaii, Indiana, Kansas, Kentucky, Louisiana, Maine, Michigan, Ohio, Nevada, New Mexico, 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 8, 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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