https://www.sfgate.com/national-parks/article/grand-canyon-rafters-sick-22346642.php
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Consensus is narrowing, however, around leptospirosis as a likely candidate. The disease is caused by the Leptospira bacteria, which infects humans and other animals through contact with soil or water contaminated by infected urine. The bacteria enters the body through cuts, scrapes or mucous membranes such as in the eyes, nose and mouth..."