I just found this on the dept of health website and thought it might be useful

Most child care related infections are more common in infants and toddlers than among older children. A study of bacterial contamination in centres found that the prevalence of faecal coliforms on hands, surfaces and in air samples was inversely related to the age of the children. The likelihood of faecal contamination was greatest on the hands of infants and carers, and least on those of the older children.38 Disposable nappies appear to be superior to cloth nappies in preventing faecal contamination of the environment.39 Whether the use of disposable nappies can reduce the incidence of diarrhoeal illness is not clear.

Two prospective studies of risk factors for diarrhoeal illness found that centres with non-toilet trained infants, and those in which food-handling staff also changed nappies, had higher diarrhoeal rates.40,41 The risk of diarrhoeal illness in three year old children who stayed in the same room as under two year olds was 4.3 (95%, CI 2.1-9.0) times greater than the risk in those separated from the under two year olds.40 In common with other enteric infections, hepatitis A outbreaks are most likely to involve centres containing many children who are still in nappies.42

Prevention of the spread of enteric infections is best achieved by ensuring that wherever possible, carers have not been involved in nappy changing prior to handling food on the same shift, that minimal contact occurs between children in nappies and older children, and that the same members of staff do not look after both age groups at the same time.