Flu | Week 7 Activity Report 2007-8

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2007-2008 Texas Influenza Surveillance Information

Influenza Surveillance Report for MMWR Week 7

The influenza (flu) activity level for Texas for the week ending February 16, 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 7. HSRs 2/3, 4/5N, 6/5S, and 9/10 reported the same level of flu activity as the previous week. HSRs 1, 7, 8, and 11 reported a decrease in flu activity from the previous week. Flu activity in Texas remains widespread overall, but activity appears to be decreasing slightly in some regions. For a map of Health Service Regions, please visit the following website:

Texas Health Service Regions Map

Laboratory Results

During week 7, thirteen hospital laboratories and public health agencies across Texas reported conducting a total of 2,722 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 2,481 antigen detection tests performed, 586 were positive for influenza A/not subtyped and 227 were positive for influenza B. These results were reported from Bell, Bexar, Collin, Dallas, Harris, Lubbock, Nueces, Tarrant, Webb, and Wilson counties. Of the 44 PCR tests performed, 7 were positive for influenza A/H3, 6 were positive influenza A/not subtyped, and 3 were positive for influenza B. These results were reported from Bell and Tarrant counties. One additional PCR test positive for influenza A/not subtyped was reported from Taylor County. The Air Force Institute for Operational Health (AFIOH) reported 2 cultures positive for influenza A/not subtyped from Texas Air Force bases in week 7. A total of 157 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, AFIOH, and other sources for the following counties:

Influenza A/H1	Influenza A/H3	Influenza A/not subtyped	Influenza B
	Angelina County	Bell County (29)	Bell County (6)
	Travis County (2)	Bexar County (16)	Bexar County (25)
		Brazos County (14)	Brazos County
		Burleson County	Dallas County (5)
		Coryell County	Harris County (5)
		Dallas County (10)	Madison County
		Harris County (14)	McLennan County (4)
		McLennan County (14)	Starr County
		Milam County (2)	Tarrant County
		Tom Green County
		Washington County
		Williamson County (2)

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]

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.

It is not too late to get a flu vaccine for the current season. Although this season‘s flu vaccine strains do not appear to be optimally matched to circulating strains, the flu vaccine may reduce the severity and duration of illness and the risk of serious complications and death due to influenza.

Influenza–Associated Pediatric Mortality

No influenza–associated pediatric fatalities occurred during MMWR week 7. As of week 7, Texas has reported five influenza–associated pediatric deaths in the 2007–08 influenza season.

School Closures and Institutional Outbreaks

One school district closed in Hopkins County due to increased influenza–like illness in week 7. No institutional outbreaks were reported.

Sentinel Provider Surveillance Network

Seventy–seven 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 7; of those, 70 (91%) providers reported seeing at least one patient with ILI. Of all patient visits during this week, 8.98% 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.