Ripples Left by H1N1: Care Utilization and Repeat Visits for Influenza-Like-Illness (ILI) in Houston, Texas (2008-2011)

In December 2007, the Houston Department of Health and Human Services (HDHHS) instituted a collaboration with local healthcare providers to enhance influenza surveillance by performing tests on specimens from patients with ILI symptoms. Kelsey-Seybold Clinic contributes the largest number of samples for this surveillance network. When H1N1 arose in April 2009, this program provided an opportunity to effectively monitor the highly publicized outbreak's impact on local patients' behavior and care utilization through number of return visits. The data used for this study comprised 3,674 patients' records with 4,046 visits obtained between August 2008 and January 2011 from Kelsey-Seybold Clinic as part of the HDHHS enhanced Influenza surveillance project. Return visits (a visit made twice or more in one season) were classified within three periods as: pre-H1N1, during H1N1, and post-H1N1. Both descriptive and inferential statistical analyses were conducted using SPSS software version 16. Results indicated that a total of 259 ILI-related return visits (6.4%) were recorded. The age category with the highest percentage of return visits was 5-24 years (3.6%). Further analyses indicated a significant difference (p<.01) in the proportion of return visits between pre-H1N1 (8.8%), H1N1 (6.3%) and post-H1N1 (3.8%). Overall, 4.8% of return visits were by patients with no vaccination history, compared to 9.1% for vaccinated patients (p<0.0001). A significant successive decline was observed in the percentage of ILI-related return visits from before to after the H1N1 period, which may reflect the delayed availability of the H1N1 vaccines, changes in CDC guidelines, media publicity, and/or the level of vaccine effectiveness during these periods.