Acute Gastroenteritis Outbreak Among Colorado River Rafters and Backpackers in the Grand Canyon, 2022

• Published in: Wilderness & environmental medicine 2024-06, Vol.35 (2), p.173-182
• Main Authors: Miko, Shanna, Calderwood, Laura, Dale, Ariella P., King, Ronan F., Maurer, Matthew B., Said, Maria A., Gebhardt, Marette, Dyer, Laurie P., Maurer, Wendy, Wikswo, Mary E., Mirza, Sara A.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Caliciviridae Infections - epidemiology; Caliciviridae Infections - transmission; Caliciviridae Infections - virology; Colorado - epidemiology; Disease Outbreaks; Female; Gastroenteritis - epidemiology; Gastroenteritis - virology; Humans; Male; Middle Aged; Norovirus; Parks, Recreational; Risk Factors; Swimming; Young Adult
• ISSN: 1080-6032; 1545-1534
• DOI: 10.1177/10806032241245093

Introduction From April 1 to May 31, 2022, Grand Canyon National Park received increased acute gastroenteritis reports. Pooled portable toilet specimens identified norovirus genogroups I and II. We sought to determine outbreak transmission contributors and individual risk factors while rafting or backpacking in the park. Methods Grand Canyon rafters and backpackers were surveyed online from June 13–July 8, 2022, and a Cox proportional hazards model was used to identify predictors associated with illness and adjusted for potential confounding factors. Results Among 762 surveys, 119 cases and 505 well persons submitted complete survey data. Illness among rafters was associated with interaction with ill persons during the trip (adjusted hazard ratio [adjHR] = 3.4 [95%CI 2.3–5.0]) and lack of any hand hygiene (1.2 [0.7–1.9]) or use of only sanitizer or water (1.6 [1.04–2.6]) before snacks. Younger rafters had higher illness rates compared to those ≥60 y (1.5 [1.2–1.8] for ages 40–59 and 2.2 [1.4–3.5] for ages