Proliferation-inducing viruses in non-permissive systems as possible causes of human cancers

Animal viruses, some of which are probably unable to replicate in human cel ls, could be transmitted to people where they may be linked to tumours curr ently not attributed to viruses. Several human virus types have oncogenic p otential in animals. A potential risk for acquiring such infections by hand ling and preparation of animal products was analysed against the background of available epidemiological reports. Human tumours should be systematical ly assessed for proliferation-inducing viruses in non-permissive systems.