An outbreak of diarrhoea due to Escherichia coli 0157:H7 in Pennsylvania in September 2000 was traced to a dairy farm open to the public where children observed and petted the animals (

). Of 51 confirmed or suspected cases 47 were under 11 years old, of whom eight developed the haemolytic-uraemic syndrome. Twenty-eight of 216 cattle on the farm were colonised with an organism that appeared to be identical to the one isolated from patients. Handwashing protected against infection. Several recent reports have suggested that farm animals are a more important source of this infection than has been realised.

A case report from Copenhagen (

; see also editorial, ibid: 609–12) has shown that mitochondrial DNA may be inherited from the father. Usually mitochondria from sperm are effectively eliminated in the early embryo by selective destruction, inactivation, or dilution by oocyte mitochondria. The Danish report describes a 28-year old man with a mitochondrial myopathy. His muscle tissue had a novel mitochondrial DNA deletion in the ND2 gene but there was no such deletion in blood lymphocytes, hair roots, or cultured fibroblasts. Sequence analysis showed that the mitochondrial DNA in the patient’s muscle was the same as his father’s mitochondrial DNA although in other tissues he had his mother’s mitochondrial DNA. His father did not have the mitochondrial DNA deletion so the gene deletion must have occurred in paternal mitochondrial DNA …