Gilleland and Walnut Creeks, in Travis County, have been identified as having elevated levels of E. coli bacteria. Health experts say swimming or ingesting water from water polluted by bacteria can cause a variety of intestinal illnesses, including stomach aches and diarrhea. Fecal bacteria can cause diseases such as gastroenteritis, ear infections, typhoid, dysentery, hepatitis A, and cholera. Therefore, it is important to decrease bacteria levels in waterways to protect human health and the environment.