The germs in the blisters and sores will cause chickenpox in a person who has never had it. Nine out of 10 adults have already had chickenpox and can't get it again, ut many children are susceptible. They could catch chickenpox if they touched the zoster rash. To be safe, keep the rash covered if possible, don't let anyone touch it, and don't share towels or washcloths. Chickenpox itself is most dangerous in the last month of pregnancy or if someone has another serious illness like AIDS or cancer.
Nobody can get zoster itself from another person with zoster.
People get zoster from themselves, from the chickenpox they had when they were young. Zoster can occur when there is even a small decline in the immune system, such as happens in early HIV infection, or just with advancing age. Some symptoms may require medical attention.