Error processing SSI file
Error processing SSI file
Error processing SSI file
Error processing SSI file
Error processing SSI file
Error processing SSI file
Error processing SSI file
Error processing SSI file

Weekly Report: Influenza Summary Update

Week ending November 8, 2003-Week 45

Error processing SSI file

The following information may be quoted:

Synopsis

Influenza activity in the United States continued to increase during week 45 (November 2 - 8, 2003). Two hundred three 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 percentage of specimens testing positive for influenza increased from 7.9% during week 44 to 19.2% for week 45. In a review of U.S. virologic surveillance data from the 1976-77 influenza season to present, this is the earliest week that the percentage of specimens testing positive for influenza has exceeded 10% nationally; the regions with the highest percentage of specimens testing positive are the West South Central region (46.5%) and the Mountain region (34.7%).

The proportion of patient visits to sentinel providers for influenza-like illness (ILI) overall was 3.2%, which is above the national baseline of 2.5%. The proportion of deaths attributed to pneumonia and influenza was 6.2%, which is below the epidemic threshold for the week. One state health department reported widespread influenza activity, 1 state reported regional activity, 8 states reported local influenza activity, 22 states, New York City, Guam, and Puerto Rico reported sporadic influenza activity, and 18 states and the District of Columbia reported no influenza activity.

Laboratory Surveillance*:

During week 45, WHO and NREVSS laboratories reported 1,056 specimens tested for influenza viruses, and 203 (19.2%) were positive. Thirty influenza A(H3N2) viruses, 170 unsubtyped influenza A viruses, and 3 influenza B viruses were identified.

Since September 28, WHO and NREVSS laboratories have tested a total of 6,024 specimens for influenza viruses and 443 (7.4%) were positive. Of the 443 viruses identified, 437 (99%) were influenza A viruses and 6 (1%) were influenza B viruses. One hundred ten (25%) of the 437 influenza A viruses have been subtyped; all were influenza A (H3N2) viruses. All 9 surveillance regions** have reported laboratory-confirmed influenza this season. Two hundred eighty-five (64%) of the 443 isolates were reported from the West South Central region and 102 (23%) were from the Mountain region.

Influenza Virus Isolated


View Chart Data

Antigenic Characterization:

CDC has antigenically characterized 55 influenza A (H3N2) viruses submitted by U.S. laboratories since September 28. Of the 55 A (H3N2) viruses tested, 9 (16%) were similar antigenically to the vaccine strain A/Panama/2007/99 (H3N2), and 46 (84%) were similar to the drift variant, A/Fujian/411/2002 (H3N2), that predominated in Australia and New Zealand during the recent Southern Hemisphere influenza season. This drift variant is related to the vaccine strain, A/Panama/2007/99. Antibodies produced against the vaccine virus cross-react with A/Fujian/411/2002-like viruses, but at a lower level. Vaccine effectiveness depends, in part, on the match between vaccine strains and circulating viruses. Although vaccine effectiveness against A/Fujian/411/2002-like viruses may be less than that against A/Panama/2007/99-like viruses, it is expected that the current U.S. vaccine will offer some cross-protective immunity against the A/Fujian/411/2002-like viruses and reduce the severity of disease.

Pneumonia and Influenza (P&I) Mortality Surveillance:

During week 45, the percentage of all deaths due to pneumonia and influenza as reported by the vital statistics offices of 122 U.S. cities was 6.2%. This percentage is below the epidemic threshold of 7.1% for week 45.

Pneumonia and Influenza Mortality

View Full Screen

Influenza-like Illness Surveillance *:

During week 45, 3.2%*** of patient visits to U.S. sentinel providers were due to ILI. This percentage is above the national baseline of 2.5%. On a regional level**, the percentage of visits for ILI was highest in the West South Central region(14.2%); all other regions were below 4%. Due to wide variability in regional level data, it is not appropriate to apply the national baseline to regional level data.

Bar Chart for Influenza-like Illness
View Chart Data

Influenza Activity as Assessed by State and Territorial Epidemiologists**:

Influenza activity was reported as widespread in 1 state (Texas), regional in 1 state (Colorado), local in 8 states (Arkansas, Louisiana, Montana, Nevada, New Mexico, Tennessee, Utah, and West Virginia). Sporadic influenza activity was reported in 22 states (Alabama, Alaska, Arizona, Connecticut, Florida, Georgia, Hawaii, Idaho, Kansas, Minnesota, Mississippi, Missouri, Nebraska, New York, North Carolina, North Dakota, Oklahoma, South Carolina, Virginia, Washington, Wisconsin, and Wyoming), New York City, Guam, and Puerto Rico. Eighteen states and the District of Columbia reported no influenza activity.

Usmap for Weekly Influenza Activity


* Reporting is incomplete for this week. Numbers may change as more reports are received.

** Surveillance 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)

*** The national and regional percentage of patient visits for ILI is weighted on the basis of state population.

Report prepared November 14, 2003

Error processing SSI file
Error processing SSI file
Error processing SSI file
Error processing SSI file