IS ACUTE LYMPHOBLASTIC-LEUKEMIA IN CHILDREN VIRUS-RELATED

The sharp peak in incidence of acute lymphoblastic leukemia at ages 2 and 3 years strongly suggests the effect of an agent, whether viral or not, to which either exposure occurs only in the earliest months of life or to which immunity develops very rapidly. Suspected clusters of childhood leukemia in the neighborhoods of two British nuclear reprocessing facilities led Leo Kinlen to postulate that large-scale immigration into areas that had previously been remote and isolated offers opportunities for spread of viral infections to which most urban populations become immune at a very early age: leukemia may be a rare manifestation of infection by one or more of such viruses. He and his group have presented evidence in support of this hypothesis. Lack of increase in childhood leukemia in the contexts of the massive evacuation of mothers and children from British cities during the Second World War, and of the considerable immigration into previously isolated islands of Greece during the last several decades, indicates that some large movements of children have occurred without providing the circumstances postulated by Kinlen. The marked inverse association of leukemia risk with birth order, noted almost 30 years ago, remains unexplained and deserves to be recalled when considering the possibility of viral involvement in the etiology of acute lymphoblastic leukemia of children.