Regional clustering of specific cancer types triggered some investigations on a potential role of infectious agents in these malignant proliferations.
Maybe I should mention it: I was not from the beginning mainly interested in papilloma virus; I was mainly interested in infectious agents in human cancer. So papilloma viruses came up as the most likely candidate from my viewpoint.
In retrospect, I have devoted my scientific life mainly to the question to what extent infectious agents contribute to human cancer, trusting that this will contribute to novel modes of cancer prevention, diagnosis and, hopefully, later on, also to cancer therapy.