Surface water sampling is an essential part of the study of waterborne pathogens. However, it’s a complex and delicate procedure that can give misleading results. A team of researchers from the Istituto Superiore di Sanità (ISS) in Italy are undertaking an evaluation of sampling methods, using the Arrone River as their test site.The Arrone River flows from Lake Bracciano (which is a drinking water reservoir) to the Tyrrhenian Sea. It’s 35km long, with a catchment area of 125km2. The surrounding land is mainly agricultural, and this, combined with two wastewater treatment plants, means that the presence of waterborne pathogens can be high.