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The cluster culprit

作者:阮切    发布时间:2019-03-07 02:12:02    

By Andy Coghlan THE hunt is on for a virus or bacterium that triggers childhood leukaemia. A major new epidemiological study has turned up the best evidence yet that leukaemia “clusters” are triggered by infections that occur in populations where many of the people are new to the area. The best known of Britain’s childhood leukaemia clusters is in the village of Seascale in Cumbria, close to the Sellafield nuclear plant, where the disease is 10 times as common as it is in Britain overall. Radiation was initially blamed, but in 1988, Leo Kinlen of the University of Oxford suggested a “population mixing” theory. When large numbers of workers move into an isolated area, Kinlen argued, the immunity passed down by migrant mothers may not prepare their children to fight off the particular strains of viruses and bacteria found in the area. Heather Dickinson and Louise Parker of the University of Newcastle have now scrutinised the health records of 120 000 children born in Cumbria between 1969 and 1989. They found that if both parents came from outside Cumbria, the chance that their child would develop leukaemia during the first 6 years of their life was 2.5 times as high as when one or both parents came from Cumbria. In areas where the population influx was heaviest, and up to 80 per cent of the parents were migrants, the risk was up to 11 times as high as in the areas with the fewest migrants. To add credence to their findings, the researchers initially excluded data from Seascale. But based on their results for the rest of Cumbria, they then predicted the number of cases in Seascale itself, given the village’s size and the number of migrants (British Journal of Cancer, vol 81, p 144). They predicted three cases of acute lymphoblastic leukaemia, rather than the six real cases. While this may not sound especially impressive, no other theory has been able to produce any sort of quantitative prediction. “I would say that Kinlen’s infection hypothesis is now established,” says Richard Doll of the University of Oxford, the epidemiologist who proved the link between smoking and lung cancer. But what infection could be the trigger? “We think it’s probably something common and that most children get over it,” says Dickinson. Researchers at the Leukaemia Research Fund’s Virus Research Centre in Glasgow are hunting for the culprit,

 

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