Influenza or Flu

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Local Information and Updates

Although reporting of flu cases to health departments is not required in Texas, WCCHD receives reports of flu throughout the year. During each flu season local, state, and federal public health agencies use enhanced surveillance systems to determine what type of influenza viruses are circulating. Enhanced surveillance allows WCCHD to monitor the progress and severity of a flu season at the community level. Enhanced flu reporting usually starts in October (week 40) and ends in May (week 20). During a pandemic reporting continues throughout the year.

Flu Surveillance by Area (Round Rock, Cedar Park/Leander, Georgetown, Taylor) provides the latest information on influenza surveillance.

Reporting Trends for Previous Flu Seasons

* Influenza-like illness (ILI) — Fever (temperature of ≥100ºF [37.8 ºC]) and a cough and/or a sore throat in the absence of a known cause other than influenza.

** Influenza (“flu”) — Illness due to influenza virus as confirmed by laboratory testing. A number of different laboratory diagnostic tests can be used for detecting the presence of influenza viruses in respiratory specimens, including direct antigen detection tests, virus isolation in cell culture, or detection of influenza-specific RNA by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR). Flu cases of all types confirmed by laboratory testing are combined under the category “total flu” for reporting purposes.

Rapid flu testing—often used in health care provider’s office or emergency room. Rapid tests may not differentiate between influenza A and influenza B. Rapid testing cannot distinguish between different subtypes of influenza A (e.g. novel H1N1 versus seasonal H1N1 versus seasonal H3N2 viruses).
rRT-PCR is a rapid method for confirming the presence of the novel H1N1 influenza A virus and seasonal influenza subtypes.
The CDC does not recommend routine subtyping of influenza illnesses. Laboratory confirmation of novel influenza A (H1N1) infection is performed for surveillance purposes and for special situations, e.g. severely ill patients, patients with immunocompromising conditions, and pregnant and breast feeding women.

The WCCHD flu surveillance system does not attempt to capture all cases of influenza or influenza-like illness. The number of reporters sending in flu reports may vary from week to week. These data should be used to look for trends over time rather than for estimating the total number of cases.

Trend charts showing the number of influenza-like illnesses and influenza cases reported during the flu season in Williamson County are posted on the website starting in September or October. Throughout the flu season, the charts may be updated for previous weeks to reflect data submitted late to WCCHD. Note that the number of reports received from school districts decreases during weeks 47, 52, 1, and 11 due to the Thanksgiving, Christmas, New Years, and Spring Break holidays respectively. The lower number of ILI and flu cases is most likely due to fewer reporters collecting surveillance data rather than an actual decrease in ILI and flu in the community.

For more information contact the WCCHD Disease Surveillance Team at (512) 943-3660 or email Mindy Powell, CDMT Team Lead.