 The results indicated that swimmers were more likely to have gastrointestinal symptoms, eye infections, skin complaints, ear, nose, and throat infections and respiratory illness than non-swimmers and in some cases, higher coliform levels correlated to higher incidence of gastrointestinal illness, although the sample sizes in these studies were small.Since then, studies have been done to confirm causative relations between swimming and certain health outcomes.A review of 22 studies in 1998 confirmed that the health risks for swimmers increased as the number of indicator bacteria increased in recreational waters and that "E. coli" and enterococci concentrations correlated best with health outcomes among all the indicators studied.