Top 5 Takeaways

  1. Largest Recorded Outbreak: This was the largest documented outbreak of acute gastroenteritis in the Grand Canyon National Park’s backcountry, affecting at least 222 rafters and backpackers, likely due to norovirus.
  2. Key Public Health Responses: Effective partnerships with river outfitters and National Park staff facilitated the implementation of control measures, including rapid case reporting, water disinfection, and promoting hand hygiene.
  3. Investigation and Findings: Initial reports in April were followed by increased cases through June. Tests on portable toilets used by rafters confirmed norovirus presence, with different genotypes identified in April and May.
  4. Control and Prevention Strategies: Public health measures included education on norovirus, promoting handwashing, isolation of ill individuals, and enhanced environmental cleaning.
  5. Challenges and Limitations: The report highlights the challenges in managing outbreaks in backcountry settings and acknowledges potential underreporting and difficulties in identifying individual cases.

Original Article Author and Citation

Corresponding Author

Ariella P. Dale,

Suggested Citation

Dale AP, Miko S, Calderwood LE, et al. Outbreak of Acute Gastroenteritis Among Rafters and Backpackers in the Backcountry of Grand Canyon National Park, April–June 2022. MMWR Morb Mortal Wkly Rep 2022;71:1207–1211. DOI: .


The report discusses an outbreak of acute gastroenteritis, primarily due to norovirus, among visitors to the Grand Canyon backcountry between April and June 2022. The outbreak, affecting rafters and backpackers, was the largest of its kind recorded in the area.


The investigation involved reviewing illness report forms, conducting a detailed survey, and testing specimens from portable toilets. Public health measures were implemented in partnership with local and national park authorities.


The outbreak’s scale and rapid spread highlight the challenges in managing public health in backcountry environments. The findings underscore the importance of rapid response, effective communication, and adherence to hygiene and sanitation protocols in preventing and controlling such outbreaks.


This significant outbreak of acute gastroenteritis in a challenging environment underscores the need for continued vigilance in public health practices, especially in settings with limited access to hygiene facilities and close contact among individuals.


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