Overview
- Multiple rafters reported prolonged illness after Colorado River trips through the Grand Canyon in May–June 2026, prompting concern among participants and online boating groups.
- Affected people described flu-like fever, severe muscle and joint aches, and in some cases localized skin infection (cellulitis) or pneumonia.
- The National Park Service says its Office of Public Health is leading an active investigation and is contacting and interviewing potentially affected visitors.
- BEACON, a crowd-sourced surveillance network, flagged spatiotemporal clustering across two independent trip groups and investigators are testing for pathogens such as Coccidioides (valley fever), dengue, hantavirus, and water- or soil-linked agents.
- No definitive cause has been identified and officials caution cases may be unrelated or reflect reporting effects; public health partners will release findings as test results and interviews clarify whether a shared exposure occurred.