Top 5 Takeaways

1. Increasing Algal Blooms: The number of harmful algal blooms is rising in the U.S., driven by higher water temperatures and nutrient runoff.
2. Seasonal Patterns: Harmful algal bloom-associated emergency department (ED) visits peak during warmer months (June–October).
3. Documentation Gaps: Most harmful algal bloom-associated ED visits (67%) were identified through chief complaint text rather than ICD-10-CM codes.
4. Demographic Insights: The majority of ED visits were among females and individuals aged 18–44 years.
5. Regional Impact: Region 4 (southeastern U.S.) had the highest number of harmful algal bloom-associated ED visits, particularly during a large red tide event in 2018.

Original Article Author and Citation

Corresponding Author

Amy M. Lavery, alavery@cdc.gov

Suggested Citation

Lavery AM, Backer LC, Roberts VA, DeVies J, Daniel J. Evaluation of Syndromic Surveillance Data for Studying Harmful Algal Bloom-Associated Illnesses — United States, 2017–2019. MMWR Morb Mortal Wkly Rep 2021;70:1191–1194. DOI: http://dx.doi.org/10.15585/mmwr.mm7035a2

Summary

This study evaluated the use of syndromic surveillance data to study health effects from harmful algal bloom exposures in the U.S. from 2017 to 2019. A total of 321 harmful algal bloom-associated ED visits were identified, with a significant increase during warmer months. The majority of visits were identified through chief complaint text rather than ICD-10-CM codes, highlighting the need for better documentation in medical records.

Methods

The study utilized data from the National Syndromic Surveillance Program (NSSP), which captures ED visit data electronically. A query was developed using chief complaint text terms and ICD-10-CM codes related to harmful algal bloom exposure. The query excluded visits associated with contaminated seafood ingestion. Basic demographic information and syndrome categories were summarized, and data were visualized by U.S. Department of Health and Human Services region and time series.

Discussion

The analysis revealed that harmful algal bloom-associated ED visits are more frequently identified through chief complaint text than ICD-10-CM codes. The peak in ED visits during 2018 corresponded with a large red tide event in the Gulf of Mexico. The findings suggest that increasing awareness among healthcare providers and patients about harmful algal bloom exposures could improve documentation and understanding of associated health effects.

Conclusion

Better documentation of harmful algal bloom exposures in medical records is essential for accurate assessment of their public health impact. Improved electronic health record systems could help monitor long-term health effects from these exposures. As harmful algal blooms become more frequent, healthcare providers should discuss and document exposures to ensure proper patient treatment and prevention.

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