Crawford L
Ciba Found Symp. 1986;120:104-16. doi: 10.1002/9780470513309.ch8.
To prove that a particular infectious agent causes a disease is much more difficult in human subjects than in other animals for both ethical and practical reasons. Where the disease is a malignant tumour with a long latent period the situation is even more difficult. For these reasons, it is often necessary to concentrate in the first instance on association of the virus with the disease, and this is discussed in the context of papillomaviruses. Association of a virus with a tumour may occur for a variety of reasons other than the virus being the cause of the tumour. This is illustrated by several examples of parvoviruses and DNA tumour viruses. Conversely, the absence of any sign of virus or viral nucleic acid in a tumour does not prove that the tumour was not induced by a virus. Apart from association of a virus with a tumour it is also necessary to show that the virus in question is oncogenic. Again this cannot normally be done directly, so that indirect evidence from animal experiments or from in vitro transformation is likely to be the best available alternative. In the final analysis the best proof of oncogenicity may be the effectiveness of intervention directed at the virus.
由于伦理和实际原因，在人体中证明某种特定的传染因子会引发疾病比在其他动物中要困难得多。如果该疾病是潜伏期很长的恶性肿瘤，情况就更加困难了。出于这些原因，通常有必要首先专注于病毒与疾病的关联，这将在乳头瘤病毒的背景下进行讨论。病毒与肿瘤的关联可能由于多种原因而发生，而不只是因为病毒是肿瘤的病因。细小病毒和DNA肿瘤病毒的几个例子说明了这一点。相反，肿瘤中没有任何病毒或病毒核酸的迹象并不能证明该肿瘤不是由病毒诱发的。除了病毒与肿瘤的关联之外，还必须证明所讨论的病毒具有致癌性。同样，这通常不能直接进行，因此来自动物实验或体外转化的间接证据可能是现有的最佳选择。归根结底，致癌性的最佳证据可能是针对该病毒的干预措施的有效性。
