(P72) EFFECT OF U.S. FEDERAL HOLIDAYS ON STI REPORTING, 2016–2022

Background:
Trends in STI surveillance data are usually examined annually to minimize surveillance artifacts that may occur at more granular levels (e.g., month or week). To describe the potential impact of U.S. federal holidays on weekly STI surveillance trends, we reviewed trends in weekly number of reported nationally notifiable STIs from 2016–2022.

Methods:
We reviewed chlamydia, gonorrhea, and primary & secondary (P&S) syphilis case notifications provided to CDC’s National Notifiable Diseases Surveillance System from 2016–2022. Cases from 2020 were excluded because of variability from the COVID-19 pandemic. Outliers were defined as weeks with counts that fell above or below set thresholds based on the distributions of weekly reported case counts by year and reported STI.  Thresholds were set using values below the first quartile minus 1.5 times the interquartile range or above the third quartile plus 1.5 times the interquartile range.

Results:
During 2016–2022, 38 outlier weeks were identified for chlamydia case notifications; 97% represented lower than average weekly case notifications. For most years, outliers occurred during weeks that included federal holidays, but in 2016 and 2022, some outliers occurred during the week before or after a federal holiday. 

For P&S syphilis, there were 14 outlier weeks that were below average; all occurred on weeks with federal holidays. Three outliers with abnormally high weekly case notifications occurred directly before and after the week of Thanksgiving in 2016 and the week after Labor Day in 2018.

For gonorrhea, only 12 weeks included outliers (none during 2017–2019); most outliers coincided with federal holidays.

Conclusion:
Variations in the annual reporting of STIs exist around federal holidays and differ by STI.  Outliers around holidays likely reflect delayed access to clinical care versus changes in disease transmission. These variations should be considered when analyzing partial year STI data to communicate trends accurately.