The strain [E. coli] O157:H7 kills 60 people a year in the USA alone. It produces toxins that cause bloody diarrhoea and can lead to kidney failure. It is likely to be more common in cattle and, following slaughter, in beef meat than previously thought. In one study, more than 80 percent of 900 calves tested had already been exposed to it, and in 13 of 15 herds tested at least one animal was infected.