Caption:A coloured scanning electron micrograph (SEM) of a group of Yersinia pseudotuberculosis bacteria.Photo credit:SCIENCE PHOTO LIBRARYCryptosporidiosis is a stomach bug that can cause diarrhoea, stomach cramps and vomiting.KATERYNA KON / SCIENCE PHOTO LIBRA / KKO / Science Photo Library via AFPFile photo.RNZ / Rebekah Parsons-King123rfWellington.123rf