Weekly Report: Influenza Summary Update

2008-2009 Influenza Season Week 42, ending October 18, 2008

(All data are preliminary and may change as more reports are received.)

Synopsis:

During week 42 (October 12-18, 2008), a low level of influenza activity was reported in the United States.

• Ten (1.0%) specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division were positive for influenza.
• The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
• The proportion of outpatient visits for influenza-like illness (ILI) was below national and region-specific baseline levels.
• Eleven states, the District of Columbia, and Puerto Rico reported sporadic influenza activity; 38 states reported no influenza activity; and one state did not report.

National and Regional Summary of Select Surveillance Components

Region	Data for current week			Data cumulative for the season
	Out-patient ILI*	% positive for flu?/strong>	Number of jurisdictions reporting regional or widespread activity?/strong>	A (H1)	A (H3)	A Unsub-typed	B	Pediatric Deaths
Nation	Normal	1.0 %	0 of 51	0	5	24	10	0
New England	Normal	0.0 %	0 of 6	0	0	0	0	0
Mid-Atlantic	Normal	0.2 %	0 of 3	0	0	1	0	0
East North Central	Normal	0.0 %	0 of 5	0	0	0	0	0
West North Central	Normal	0.0 %	0 of 7	0	0	0	0	0
South Atlantic	Normal	0.4 %	0 of 9	0	0	2	2	0
East South Central	Normal	0.0 %	0 of 4	0	0	0	0	0
West South Central	Normal	0.7 %	0 of 4	0	0	5	0	0
Mountain	Normal	4.1 %	0 of 8	0	5	3	3	0
Pacific	Normal	2.1 %	0 of 5	0	0	13	5	0

* Elevated means the % of visits for ILI is at or above the national or region-specific baseline
?National data is for current week; regional data is for the most recent three weeks.
?Includes all 50 states and the District of Columbia

U.S. Virologic Surveillance:

During week 42, WHO and NREVSS laboratories located in all 50 states and Washington D.C. reported 999 specimens tested for influenza viruses, 10 of which were positive: one influenza A (H3) virus (Mountain region), eight influenza A viruses that were not subtyped (Mountain, Pacific, and West South Central regions) and one influenza B virus (Pacific region).

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Pneumonia and Influenza (P&I) Mortality Surveillance

During week 42, 6.3% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage is below the epidemic threshold of 6.6% for week 42.

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Influenza-Associated Pediatric Mortality

No influenza-associated pediatric deaths were reported during week 42.

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Influenza-Associated Hospitalizations

Laboratory-confirmed influenza-associated hospitalizations are monitored in two population-based surveillance networks: the Emerging Infections Program (EIP) and the New Vaccine Surveillance Network (NVSN). EIP and NVSN estimated rates of hospitalization for influenza will be reported every two weeks starting later this season.

Outpatient Illness Surveillance:

During week 42, 1.1% of patient visits reported through the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) (formally known as the U.S. Influenza Sentinel Provider Surveillance Network) were due to influenza-like illness (ILI). This percentage is less than the national baseline of 2.4%. On a regional level, the percentage of visits for ILI ranged from 0.5% to 2.4%. All nine regions reported percentages of visits for ILI below their respective region-specific baselines.

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Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists:

During week 42 the following influenza activity was reported:

• Sporadic activity was reported in the District of Columbia, Puerto Rico, and 11 states (Alaska, California, Colorado, Connecticut, Florida, Hawaii, Indiana, Texas, Utah, Washington, and West Virginia).
• No influenza activity was reported in 38 states (Alabama, Arizona, Arkansas, Delaware, Georgia, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Vermont, Virginia, Wisconsin, and Wyoming).
• One state did not report (Idaho).

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A description of surveillance methods is available at: http://www.cy118119.com/flu/weekly/fluactivity.htm

• Page last updated October 24, 2008.
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