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 March 20, 2004-Week 11

Error processing SSI file

The following information may be quoted:

Synopsis:

Influenza activity remained low during the week of March 14-20, 2004. The percentage of patient visits for influenza-like illness (ILI) has remained below the national baseline (2.5%) for 10 consecutive weeks. During week 11, mortality due to pneumonia and influenza (P&I) remained below the epidemic threshold (8.3%). Four (0.3%) of 1,189 specimens collected from throughout the United States and tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories were positive for influenza. Twenty-one states, New York City, Guam, and Puerto Rico reported sporadic activity and 29 states and the District of Columbia reported no influenza activity.

Laboratory Surveillance*:

During week 11, WHO and NREVSS laboratories reported 1,189 specimens tested for influenza viruses, and 4 (0.3%) were positive. Of these, 1 was an influenza A virus that was not subtyped and 3 were influenza A (H3N2) viruses.

Since September 28, 2003, WHO and NREVSS laboratories have tested 113,517 specimens for influenza viruses, of which 24,108 (21.2%) were positive. Of these, 23,932 (99.3%) were influenza A viruses, and 176 (0.7%) were influenza B viruses. Of the 23,932 influenza A viruses, 6,818 (28.5%) have been subtyped; 6,816 (99.9%) were influenza A (H3N2) viruses and 2 (0.1%) were influenza A (H1) viruses.

Influenza Virus Isolated


View Chart Data

Antigenic Characterization:

CDC has antigenically characterized 757 influenza viruses collected by U.S. laboratories since October 1, 2003: three influenza A (H1) viruses, 727 influenza A (H3N2) viruses, and 27 influenza B viruses. The hemagglutinin proteins of the influenza A (H1) viruses were similar antigenically to the hemagglutinin of the vaccine strain A/New Caledonia/20/99. Of the 727 influenza A (H3N2) isolates that have been characterized, 106 (14.6%) were similar antigenically to the vaccine strain A/Panama/2007/99 (H3N2), and 621 (85.4%) were similar to the drift variant, A/Fujian/411/2002 (H3N2). Twenty-four influenza B viruses characterized were similar antigenically to B/Sichuan/379/99 and 3 were similar antigenically to B/Hong Kong/330/2001.

Pneumonia and Influenza (P&I) Mortality Surveillance:

During week 11, 7.2% of all deaths reported by the vital statistics offices of 122 U.S. cities were due to pneumonia and influenza. This percentage is below the epidemic threshold of 8.2% for week 11.

Pneumonia And Influenza Mortality

View Full Screen

Influenza-like Illness Surveillance *:

The percentage of patient visits to approximately 1,000 U.S. sentinel providers nationwide for ILI was 1.2%** during week 11, the tenth consecutive week this indicator has been below the national baseline of 2.5%. The percentage of patient visits for ILI in each of the nine surveillance regions*** was below 2.0%. 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 | View Full Screen

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

There were no reports of widespread, regional, or local activity for week 11. Sporadic activity was reported in 21 states (Arizona, California, Colorado, Hawaii, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Montana, Nevada, New Mexico, New York, North Dakota, Ohio, Texas, Utah, and West Virginia), New York City, Guam, and Puerto Rico. All other states and the District of Columbia reported no influenza activity.

U. S. map for Weekly Influenza Activity
View Full Screen

--------------------------------------------------------------------------------

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

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

*** 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)

Report prepared March 25, 2004

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