Week 06

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2007-2008 Texas Influenza Surveillance Information

Influenza Surveillance Report for MMWR Week 6

The influenza (flu) activity level for Texas for the week ending February 9, 2008 is “widespread.” Widespread activity indicates that at least half of the regions in the state are experiencing an increase in influenza–like illness (ILI) and have recent culture–confirmed influenza.

Reports were received from all 11 Health Service Regions (HSRs) for week 6. HSRs 1, 2/3, 8, and 9/10 reported an increase in flu activity from the previous week. HSR 7 reported a decrease in flu activity compared to the previous week. For a map of Health Service Regions, please visit the following website:

Texas Health Service Regions Map

During week 6, eight hospital laboratories and public health agencies across Texas reported conducting a total of 2,421 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 2,142 antigen detection tests performed, 591 were positive for influenza A/not subtyped and 121 were positive for influenza B. These results were reported from Bell, Bexar, Harris, Lubbock, Tarrant, and Webb counties. Of the 53 PCR tests performed, 3 were positive for influenza A/H3, 9 were positive influenza A/not subtyped, and 11 were positive for influenza B. These were reported from patients residing in Bell, Coryell, McLennan, Tarrant, Travis, and Williamson counties. Additional PCR tests positive for influenza A/not subtyped and influenza B were reported from Tarrant County. A total of 306 reports of culture–confirmed influenza were received from NREVSS, the Texas Department of State Health Services (DSHS) Laboratory, Scott and White Hospital Laboratory, Texas Children‘s Hospital Laboratory, University Hospital, 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/. It is too early in the season to tell how well circulating strains will match the vaccine strains, or which influenza viruses will predominate this season. The DSHS Laboratory sends a representative sample of influenza viruses to the CDC throughout the flu season.

Influenza–Associated Pediatric Mortality

One influenza–associated pediatric fatality occurred during MMWR week 6. The death occurred in a 14–year–old resident of Ellis County. The child had no significant underlying medical conditions prior to illness onset; however, a sputum specimen obtained during the illness was positive for methicillin resistant Staphylococcus aureus (MRSA). The child was not vaccinated for influenza for the current season. A direct fluorescent antibody test was positive for influenza A/not subtyped. As of week 6, Texas has reported five influenza–associated pediatric deaths in the 2007–08 influenza season.

School Closures and Institutional Outbreaks

School closures due to increased influenza–like illness were reported in Comanche (four schools), Hale (one school), and Wood (one school) counties in week 6. Institutional outbreaks due to influenza–like illness were reported in two Collin County schools (the schools remained open). 

Sentinel Provider Surveillance Network

Seventy–five sentinel providers 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 6; of those, 70 (93%) providers reported seeing at least one patient with ILI. Of all patient visits during this week, 9.74% were due to ILI. 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

The map showing influenza activity in the United States for MMWR week 6:

 
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 6:

*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, 02/16/08, 02/23/08, 03/01/08, 03/08/08, 03/15/08, 03/22/08, 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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