An infectious cause for childhood leukaemia has long been suspected and a research letter published in 17 March
Kinlen and Balkwill compared the incidence of childhood leukaemia in two populations in Orkney and Shetland, UK during and after World War II. During the war, local people were outnumbered by servicemen stationed there in case of a northern invasion. This favoured unusual rural–urban population mixing, which increases contacts between susceptible individuals (more prevalent in rural areas) and possible infected individuals. The authors found that childhood leukaemia increased 3·6-fold (
The findings are consistent with those in other examples of unusual rural–urban population mixing and suggest an underlying infectious cause in childhood leukaemia. The agent remains to be identified.