 That HIV causes AIDS does not follow from Koch's postulates, which may have supported HIV/AIDS denialism.The role of oncoviruses in causing some cancers also does not follow Koch's postulates.While Koch's postulates have served the microbiology community well for nearly two centuries, new discoveries of methods of infections as a result of Koch and many others' hard work have shown that diseases and certain conditions are not always caused by one lonesome microbe species.