"Why has it been so difficult to identify infectious agents as cancer-inducing factors in humans? Because there is no human pathogenic infectious agent causing cancer as the acute consequence of infection ... Infections linked to human cancers are common in human populations, most of them were present during the whole human evolution,and only a small proportion of infected individuals develops the respective cancer type ... Except for rare germline mutations, (XLLP), cancers linked to infection commonly occur decades after primary infection ..."