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Centers for Disease Control and Prevention


Influenza Summary Update

(Week ending October 21, 2000-Week 42)


The following information may be quoted:

Synopsis: During week 42 (October 15-21, 2000), none of the specimens tested by WHO and NREVSS laboratories were positive for influenza 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 6.8%. This percentage is below the epidemic threshold for this time of year. Twelve state and territorial health departments reported sporadic influenza activity and 37 reported no influenza activity.

U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) Collaborating Laboratory Reports*: During week 42, WHO and NREVSS laboratories reported 625 specimens tested for influenza viruses. No influenza isolates were identified.

Pneumonia and Influenza (P&I) Mortality: During week 42, the percentage of all deaths due to P&I as reported by the vital statistics offices of 122 U.S. cities was 6.8%. This percentage is below the epidemic threshold of 7.4% for week 42.

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 42, 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.

Influenza Activity as Assessed by State and Territorial Epidemiologists**: Influenza activity was reported as sporadic in 12 states (Colorado, Florida, Hawaii, Kansas, Kentucky, Louisiana, Ohio, Nevada, New Hampshire, New Mexico, Texas, and West Virginia). Thirty-seven states reported no influenza activity, and 1 did not report.




* 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: October 26, 2000



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

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