Week 12

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2007-2008 Texas Influenza Surveillance Information

Influenza Surveillance Report for MMWR Week 12

The influenza (flu) activity level for Texas for the week ending March 22, 2008 was “regional.” During week 12, 104 (18.1%) specimens tested by NREVSS laboratories in Texas were positive for influenza. Of all the specimens that were positive for influenza, 87 (83.7%) were positive for influenza B. The percentage of visits due to influenza–like illness (ILI) as reported by SPSN providers in Texas was below baseline. Flu activity in Texas in week 12 continued to decrease in all regions.

Reports from Health Service Regions

Reports were received from all 11 Health Service Regions (HSRs) for week 12. All regions reported a decrease in flu activity compared to week 11. For a map of Health Service Regions, please visit the following website:

Texas Health Service Regions Map

Laboratory Results

During week 12, nine hospital laboratories and public health agencies across Texas reported conducting a total of 576 influenza tests (antigen, culture, and PCR) to the National Respiratory and Enteric Virus Surveillance System (NREVSS) sponsored by the Centers for Disease Control and Prevention (CDC). Of the 512 antigen detection tests performed, 12 were positive for influenza A/not subtyped and 72 were positive for influenza B. These results were reported from Bell, Bexar, Collin, Harris, Hunt, Lubbock, and Nueces counties. Positive PCR results for influenza A/not subtyped and influenza B were reported from Tarrant County. A total of 19 reports of culture–confirmed influenza were received from the Texas Department of State Health Services (DSHS) Laboratory, Scott and White Hospital Laboratory, Texas Children’s Hospital Laboratory, NREVSS, and other sources for the following counties:

Additional positive results from point-of-care rapid flu tests were reported by providers throughout the state (see Texas map below).

Antigenic Characterization

CDC has reported antigenic characterization results from 34 influenza isolates [7 influenza A/H1, 24 influenza A/H3, and 3 influenza B viruses] received from the DSHS Laboratory since the beginning of the 2007–08 flu season.

Influenza A/H1 [7]

• Seven (100%) of the seven viruses were characterized as A/Solomon Islands/3/2006, the influenza A/H1 component of the 2007–08 influenza vaccine for the Northern Hemisphere.

Influenza A/H3 [24]

• Two (8%) of the 24 viruses were characterized as A/Wisconsin/67/2005–like, the influenza A/H3 component of the 2007–08 influenza vaccine for the Northern Hemisphere.
• Twenty–one (88%) of the 24 viruses were characterized as A/Brisbane/10/2007–like. A/Brisbane/10/2007 is a recent antigenic variant which evolved from A/Wisconsin/67/2005–like.
• One (4%) of the 24 viruses showed somewhat reduced titers with antisera produced against A/Wisconsin/67/2005 and A/Brisbane/10/2007.

Influenza B (B/Victoria/02/87 and B/Yamagata/16/88 lineages) [3]

Victoria lineage [0]
• The influenza B component for the 2007–08 influenza vaccine is a B/Malaysia/2506/2004–like virus, belonging to the B/Victoria lineage.
  Yamagata lineage [3]
• Three (100%) of the three viruses were identified as belonging to the B/Yamagata lineage of viruses.
  

These results are very similar to national antigenic characterization results. The national results may be found in the CDC weekly flu report at  http://www.cdc.gov/flu/weekly/. The DSHS Laboratory sends a representative sample of influenza viruses to the CDC throughout the flu season.

Influenza–Associated Pediatric Mortality

No influenza–associated pediatric fatalities occurred during MMWR week 12. As of week 12, Texas has reported six influenza-associated pediatric deaths in the 2007–08 influenza season.

School Closures and Institutional Outbreaks

During week 12, an outbreak of influenza occurred among residents and staff in a Dallas County long–term care facility. Rapid flu tests were positive for influenza A/not subtyped; viral cultures were collected and the results are pending. No new cases of influenza have been reported.

No school closures were reported during week 12.

Sentinel Provider Surveillance Network

Sixty–three sentinel providers in Texas reported data to the U.S. Influenza Sentinel Provider Surveillance System (SPSN) on patients with influenza–like illness (ILI) and total patients seen for any reason during week 12. Of the 62 providers who reported seeing patients during week 12, 37 (60%) saw at least one patient with ILI. Of all patient visits during this week, 2.84% were due to ILI. This is the first time since week 51 (mid–December) that the percentage of visits due to ILI has fallen below the regional baseline. The ILI baseline for the West South Central Region (Arkansas, Louisiana, Oklahoma, and Texas) of the United States is 4.3% for the 2007–2008 season. The baseline is the mean percentage of patient visits for ILI during non–influenza weeks for the previous three seasons plus two standard deviations.

National Influenza Activity Map

For more information on flu surveillance activities in the State of Texas, please visit our main surveillance page.

The map showing influenza activity in the State of Texas for MMWR week 12:

*Influenza activity level corresponds to current MMWR week only and does not reflect previous weeks' activity.

2007-2008 Texas Influenza Surveillance Information - Flu Reports

For the week ending: 
10/06/07, 10/13/07, 10/20/07, 10/27/07, 11/03/07, 11/10/07, 11/17/07, 11/24/07, 12/01/07, 12/08/07, 12/15/07, 12/22/07, 12/29/07, 01/05/08, 01/12/08, 01/19/08, 01/26/08, 02/02/08, 02/09/08, 02/16/08, 02/23/08, 03/01/08, 03/08/08, 03/15/08, 03/29/08, 04/05/08, 04/12/08, 04/19/08, 04/26/08, 05/03/08, 05/10/08, 05/17/08

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