The recurrence rate of shingles is generally 0, which means that in most cases shingles does not recur and a person will only have one episode in their lifetime, or two or more in a very small number of people. Like chickenpox, shingles is caused by the varicella-zoster virus, and like chickenpox, shingles has lifelong immunity, meaning it only occurs once in a lifetime. Similar diseases include measles and leprosy. In practice, a very small number of people have the possibility of developing shingles twice due to their very low resistance, such as patients who use immunosuppressive drugs for a long time, but for the general population shingles does not recur.