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Weekly Report: Influenza Summary Update

Week ending November 4, 2006-Week 44

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Synopsis:

During week 44 (October 29 – November 4, 2006)*, a low level of influenza activity was reported in the United States. Eighty-four (4.8%) 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) and the proportion of deaths attributed to pneumonia and influenza were below baseline levels. One state reported regional influenza activity; two states reported local influenza activity; 12 states and the District of Columbia reported sporadic influenza activity; 34 states and New York City reported no influenza activity; and one state did not report.

Laboratory Surveillance*:

During week 44, WHO and NREVSS laboratories reported 1,743 specimens tested for influenza viruses, 84 of which were positive: five influenza A (H1) viruses, one influenza A(H3) virus, 58 influenza A viruses that were not subtyped, and 20 influenza B viruses.

Since October 1, 2006, WHO and NREVSS laboratories have tested a total of 8,937 specimens for influenza viruses and 276 (3.1%) were positive. Among the 276 influenza viruses, 218 (79.0%) were influenza A viruses and 58 (21.0%) were influenza B viruses. Fifty-five (25.2%) of the 218 influenza A viruses have been subtyped: 49 (89.1%) were influenza A (H1) viruses and 6 (10.9%) were influenza A (H3) viruses. Of the 276 influenza viruses reported this season, 180 (65.2%) have been reported from Florida. Nineteen states from eight of the nine surveillance regions** have reported laboratory confirmed influenza this season.

INFLUENZA Virus Isolated


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Antigenic Characterization:

Since October 1, 2006, CDC has antigenically characterized one influenza virus collected by U.S. laboratories. The influenza A (H1) virus was characterized as A/New Caledonia/20/99 -like, which is the influenza A (H1) component recommended for the 2006-07 influenza vaccine.

Pneumonia and Influenza (P&I) Mortality Surveillance*:

During week 44, 6.02% of all deaths were reported as due to pneumonia or influenza. This percentage is below the epidemic threshold of 6.65% for week 44.

Pneumonia And Influenza Mortality

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Influenza-Associated Pediatric Mortality*:

No influenza-associated pediatric deaths were reported for week 44.

Influenza-Associated Pediatric Hospitalizations*:

Laboratory-confirmed influenza-associated pediatric hospitalizations are monitored in two population-based surveillance networks: the Emerging Infections Program (EIP) and the New Vaccine Surveillance Network (NVSN). No influenza-associated pediatric hospitalizations have been reported from the EIP. NVSN estimated rates of hospitalization for influenza will be reported every 2 weeks, beginning December 2006.

Influenza-like Illness Surveillance*:

During week 44, 1.3%*** of patient visits to U.S. sentinel providers were due to ILI. This percentage is less than the national baseline**** of 2.1%. On a regional level**, the percentage of visits for ILI ranged from 0.6% to 2.2% with no regions above their region-specific baseline****.

Bar Chart for Influenza-like Illness
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Influenza Activity as Assessed by State and Territorial Epidemiologists*:

During week 44, the following influenza activity was reported:

• Regional activity was reported by North Carolina.
• Local activity was reported by two states (Florida and Louisiana).
• Sporadic activity was reported by the District of Columbia and 12 states (California, Connecticut, Hawaii, Indiana, Kentucky, Maryland, Massachusetts, Mississippi, New York, Pennsylvania, Texas, and Virginia).
• No influenza activity was reported by New York City and 34 states.
• No reports were received from one state.

U. S. map for Weekly Influenza Activity
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Foot notes

Report prepared November 09, 2006 Error processing SSI file
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