Week ending October 18, 2003-Week 42

The following information may be quoted:

Synopsis: During week 42 (October 12 ?18, 2003)*, 15 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories were positive for influenza. The proportion of patient visits to sentinel providers for influenza-like illness (ILI) overall was 1.9%, which is less than the national baseline of 2.5%. The proportion of deaths attributed to pneumonia and influenza was 6.3%. One state health department (Texas) reported widespread influenza activity, 5 states and New York City reported sporadic influenza activity, and 40 states and the District of Columbia reported no influenza activity.

Laboratory Surveillance*: During week 42, WHO and NREVSS laboratories reported 520 specimens tested for influenza viruses, and 15 (2.9%) were positive. Eleven influenza A(H3N2) and 4 unsubtyped influenza A viruses were identified.

Since September 28, WHO and NREVSS laboratories have tested a total of 1,980 specimens for influenza viruses and 70 (3.5%) were positive. Of the 70 viruses identified, 69 (99%) were influenza A viruses and 1 (1%) was an influenza B virus. Fourteen (20%) of the 69 influenza A viruses have been subtyped; all were influenza A (H3N2) viruses. Sixty-six (94%) of the 70 isolates were reported from the East South Central region**. Six states have reported laboratory-confirmed influenza during October. Influenza A viruses have been identified in Arkansas, Louisiana, New York, Texas, and Washington. An influenza B virus has been identified in Hawaii.

In the 2 previous influenza surveillance reports, CDC incorrectly reported influenza A viruses from Washington State during September. Although influenza A viruses have been identified in Washington State during October, there were no influenza A viruses reported from Washington State in September.

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Pneumonia and Influenza (P&I) Mortality Surveillance: During week 42, the percentage of all deaths due to pneumonia and influenza as reported by the vital statistics offices of 122 U.S. cities was 6.3%. This percentage is below the epidemic threshold of 6.8% for week 42.

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Influenza-like Illness Surveillance *: During week 42, 1.9%*** of patient visits to U.S. sentinel providers were due to ILI. This percentage is less than the national baseline of 2.5%. On a regional level**, the percentage of visits for ILI ranged from 0.5% to 7.0%. Due to wide variability in regional level data, it is not appropriate to apply the national baseline to regional level data.

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Influenza Activity as Assessed by State and Territorial Epidemiologists**: Influenza activity was reported as widespread in 1 state (Texas) and sporadic in 5 states (Arizona, Arkansas, Louisiana, Nebraska, and New York) and New York City. Forty states and the District of Columbia reported no influenza activity, and 4 states did not report.