Researchers from the University of Zaragoza (Spain) have analysed drinking water and detected oocysts of Cryptosporidium and cysts of Giardia, two protozoa that cause outbreaks of diarrhoea in humans. The levels detected are very low and do not represent a health risk; however, according to the study, the ubiquity of these parasites and the inefficiency of conventional water treatment in reducing them may present a public health issue.