Surveillance

The state of Texas participates in conducting influenza surveillance by reporting the estimated level of influenza activity to the CDC every week during flu season (October to May). Influenza activity levels are reported as no activity, sporadic, local, regional, or widespread based on the definitions noted below. There are 11 health service regions in Texas. The Infectious Disease Control Unit (IDCU) of the Texas Department of State Health Services (DSHS), in cooperation with the DSHS Medical Virology Laboratory, monitors influenza around the state. Texas currently has culture surveillance sites in Amarillo, Austin, Corpus Christi, Dallas, El Paso, Fort Worth, Galveston, Laredo, Lubbock, San Antonio, Tyler, and Wichita Falls. Health care providers at participating sites collect and submit viral cultures to the DSHS lab on a weekly basis during flu season. There is also the CDC-sponsored Sentinel Provider Surveillance Network (SPSN) in Texas that has over 120 providers who voluntarily report outpatient influenza-like illness by age group to the CDC on a weekly basis; some providers also submit cultures to the DSHS lab. Other laboratories, regional and local health departments, facilities participating in influenza research, and private physicians around the state also participate in flu surveillance. It is through these efforts of health care providers and laboratories in Texas and all other states, that the CDC develops a national picture of influenza virus activity, the geographic distribution of influenza viruses, and the clinical impact of the circulating viruses.

Influenza Activity Levels

† Lab confirmed case = case confirmed by rapid diagnostic test, antigen detection, culture, or PCR. Care should be given when relying on results of point of care rapid diagnostic test kits during times when influenza is not circulating widely. The sensitivity and specificity of these tests vary and the positive predictive value may be low outside the time of peak influenza activity. Therefore, a state may wish to obtain laboratory confirmation of influenza by testing methods other than point of care rapid tests for reporting the first laboratory confirmed case of influenza of the season. During periods of elevated influenza activity, the positive predictive value of rapid point of care tests will be higher.

* Influenza-Like-Illness (ILI) activity can be assessed using a variety of data sources including sentinel providers, school/workplace absenteeism, and other syndromic surveillance systems that monitor influenza-like illness.

‡ Institution includes nursing home, hospital, prison, school, etc.

**Region: population under surveillance in a defined geographical subdivision of a state. A region could be comprised of 1 or more counties and would be based on each state's specific circumstances. Depending on the size of the state, the number of regions could range from 2 to approximately 12. The definition of regions would be left to the state but existing state health districts could be used in many states. Allowing states to define regions would avoid somewhat arbitrary county lines and allow states to make divisions that make sense based on geographic population clusters. Focusing on regions larger than counties would also improve the likelihood that data needed for estimating activity would be available.

Influenza surveillance questions may be directed to  , Influenza Coordinator, or , Influenza Surveillance Coordinator, at 512-458-7676. Questions about the Sentinel Provider Surveillance Network (SPSN) may be directed to   at 512-458-7676.

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