A study in southeast Michigan looked at ways to tell if high levels of E. coli in water were from recent poop contamination or just bacteria already in the water. They used a new test that can detect any kind of poop, not just from humans or animals. By testing five beaches, they found that this new test could tell the difference between fresh poop contamination and bacteria already in the water. This helps public health officials keep swimmers safe from harmful bacteria in the water.