Week 05

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2007-2008 Texas Influenza Surveillance Information

Influenza Surveillance Report for MMWR Week 5

The influenza (flu) activity level for Texas for the week ending February 2, 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 5. All regions reported an increase in flu activity from the previous week. For a map of Health Service Regions, please visit the following website:

Texas Health Service Regions Map

Laboratory Results

During week 5, eleven hospital laboratories across Texas reported conducting a total of 2,130 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). Five hundred and twenty–nine antigen detection tests positive for influenza A/not subtyped and ninety–one antigen detection tests positive for influenza B were reported from Bell, Bexar, Dallas, Collin, Harris, Lubbock, Nueces, Webb, and Wilson counties. Ten PCR tests positive for influenza A/not subtyped were reported from patients residing in Bell, McLennan, and Williamson counties. Additional PCR tests positive for influenza A/not subtyped and influenza B were reported from Tarrant County. The Air Force Institute for Operational Health (AFIOH) reported 12 cultures positive for influenza A/not subtyped, 3 cultures positive for influenza A/H3, and 5 cultures positive for influenza B from Texas Air Force bases in week 5. A total of 304 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, AFIOH, 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 33 influenza isolates [7 influenza A/H1, 23 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 [23]

• Two (9%) of the 23 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 (91%) of the 23 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.

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

Two influenza–associated pediatric fatalities occurred during MMWR week 5. The first death occurred in a 10–year–old resident of Parker County who had no significant underlying medical conditions. The child had not been vaccinated for the current flu season. The child tested positive for influenza B by rapid flu test. The second death occurred in a 4–month–old resident of Tarrant County who had no significant underlying medical conditions. The child was too young to be vaccinated for influenza. The child tested positive for influenza A/not subtyped by rapid flu test. As of week 5, Texas has reported four 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 Dallam (one school), Henderson (multiple schools), Smith (one school), and Travis (one school) counties in week 5. One institutional outbreak due to influenza–like illness was reported in a Johnson County elementary school (the school remained open).

Sentinel Provider Surveillance Network

Seventy–six 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 5; of those, 69 (91%) providers reported seeing at least one patient with ILI. Of all patient visits during this week, 10.38% 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 5:

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 5:

*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, 02/09/08, 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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