**4. Disadvantages in relying solely on** *E. coli* **to monitor water contamination**

Although historically total coliforms, faecal coliforms, *Enterococci* and *E. coli* have all been used as indicator organism for faecal water pollution and currently employed methods continue to largely rely on these, it is clear that alternative indicators need to be developed to address limitations in identifying other water contaminants of considerable public health concerns. Water‐borne diseases including diarrhoea and gastrointestinal illness can be caused by bacteria, viruses and protozoa [4]. Approximately 3.4 million people, mainly children, die from water‐borne diseases [66] and solely relying on *E. coli* can result in misleading information [67]. Major etiological agents including *Giardia*, *Cryptosporidium*, *Vibrio cholerae* and *Salmonella* would be missed by current testing procedures. Often outbreaks are due to local flood or storm events or releases of untreated sewage which result in significant contamination of environmental water. Worldwide morbidity and mortality caused by contaminated drinking water is of considerable magnitude. The WHO ranks diarrhoeal diseases sixths highest in the list of causes of environmental deaths with an estimate of 846,000 deaths annually [68]. This highlights the need for a concentrated effort to make both recreational and drinking water safe in both developing and developed countries [4]. The development of methods detecting a wide range of significant pathogens is most likely to be achieved by extraction and antibody based detection, as described for pathogenic protozoa [69] or molecular techniques such as PCR, shown for *Cryptosporidium parvum* and *Giardia lamblia* [70], and with further developments of NGS and MALDI. However, the advantage of the currently used *E. coli–*based procedures is their simplicity, low cost and functionality for rapid onsite detection. Additional more broad ranging tests would need to be rigorously assessed in a wide variety of environmental situations before they could be adapted as international standards. There is, therefore, a clear need to re‐examine the precision and reproducibility of both culture and molecular-based methods in the assessment of environmental samples to take into account local variations and design new methods to be applicable for a wide range of scenarios in order to make a significant contribution to improving water safety globally.
