During their lifetime about 30% of Americans will develop herpes zoster, which translates into an estimated 1 million cases each year in this country. The risk of zoster increases with increasing age; about half of all cases occur among people age 60 years or older. People who are immunosuppressed, including those with leukemia, lymphoma, and human immunodeficiency virus (HIV) infection, and people who receive immunosuppressive drugs, such as steroids and cancer chemotherapy, also are at greater risk of zoster. Most people have only one episode of shingles. The risk of recurrence is low in people who are not immunosuppressed, but the precise incidence is unknown.