International field data suggest that up to one out of every four piglets dies before weaning. After accounting for stillbirths, crushing and piglets that die because they do not get enough to drink or are too weak to survive, most of the remainder die of scours. In the first week of life most scours are caused by Escherichia coli. Data have suggested that up to 50% of these scour deaths are caused by the K88 type E. coli, accounting directly for the deaths of about 150 thousand piglets per year in the U.K. and over 10 million worldwide.

Field observations have suggested that only some litters are affected while others remain healthy even though they are reared alongside litters with K88 scour. Similarly, it has been observed that the progeny from certain boars are more susceptible.