Epidemiological evidence for an infective basis in childhood leukaemia

TLDR: In several vertebrate species, the specific agents responsible for leukaemia belong to a class that is notoriously difficult to isolate as discussed by the authors, and many infectious illnesses do not cluster because they are uncommon responses to the relevant infection.

Abstract: An infective basis for childhood leukaemia is not a new suspicion (Kellett, 1937). The failure of microbiologists to identify any specific agent and of epidemiologists to demonstrate marked space-time clustering of the disease (Smith, 1982) have been discouraging, but neither is incompatible with an infectious origin. In several vertebrate species, the specific agents responsible for leukaemia belong to a class that is notoriously difficult to isolate. Also, many infectious illnesses do not cluster because they are uncommon responses to the relevant infection. Thus, the agent responsible for infectious mononucleosis is mainly spread not by those with the illness but by that very much larger number of infected individuals who are clinically unaffected (or only trivially so). Such infections can be considered as 'mainly immunising': they can be seen as representing the most probable broad category to which the infection underlying childhood leukaemia belongs.