There are several things that influence how well-suited a microbe is to causing a disease. The ability of a microbe to cause disease is termed pathogenicity. This is a qualitative description. For example, some microbes are pathogenic, meaning they can harm you and cause you a disease. They're like the alcoholic drinks at the casino that will end up hurting you the morning after you drink them. This is in contrast to non-pathogenic microbes that will not cause you any harm. This is akin to the non-alcoholic drinks that you may encounter at a casino.