Zoster is caused by reactivation of a latent varicella virus infection (from having chickenpox in the past). Zoster is not passed from one person to another through exposure to another person with zoster. However, if a person who is susceptible to chickenpox (i.e., they had never had chickenpox and were not vaccinated against chickenpox) comes in direct contact with a person with a zoster rash, the virus could be transmitted to the susceptible person. The exposed person would develop chickenpox, not zoster. Covering the zoster rash reduces the chances of transmitting varicella zoster virus.