Deadly import

 作者:水瞍     |      日期:2019-03-07 06:10:00
By Emma Young A study of leukaemia cases in northern Scotland during World War II provides more evidence that the disease is caused by an infectious agent, says a British team. During the war, British servicemen flooded into the Shetland and Orkney isles, outnumbering the local population. Leo Kinlen and his team at Oxford University found that cases of leukaemia in children under five increased six-fold between 1941 and 1945. The number of cases in children aged up to 14 increased by 3.6 times. These extra cases would be expected if an infection causes the cancer, says Kinlen. More than a dozen other studies of sudden influxes of large numbers of people into established populations have also found two to threefold increases in childhood leukaemia. “Our number is slightly higher than that found in other studies. But these were unusually isolated people. For many of them, it was their first contact with outsiders,” Kinlen told New Scientist. If leukaemia is caused by an infectious agent it is clear that many people carry the bacterium or virus without becoming ill, Kinlen says. In a city, people would be exposed far more frequently, producing a steady stream of cases. But when the agent arrived in an isolated population, none of whom had been exposed to it, the disease could rage through the community, he says. Kinlen suspects that a virus is probably to blame. Viruses are known to cause leukaemia in many animals, including cats and cows. They are also known to cause cancers in humans, including liver, stomach and cervical cancer. But no one has yet managed to pin down a viral cause of leukaemia in people. British scientists have suggested that the influx of workers into the village of Seascale close to the Sellafield nuclear power plant in Cumbria, UK, may explain the observed local increase in the disease (New Scientist magazine, 21/8/99). Many locals have blamed raised levels of radioactivity. More at: The Lancet (vol 357,