Summer Floods, Swimming Holes, and Outdoor Adventures Are Creating the Perfect Conditions for a Waterborne Bacterial Disease That Most Americans Have Never Heard Of

Leptospirosis — caused by bacteria in animal urine that contaminate soil, water, and flood zones — peaks in summer outdoor activity season. The CDC updated leptospirosis prevention guidance in February 2026. Globally, it kills 60,000 annually. Here is what summer adventurers, flood victims, and outdoor enthusiasts must know.