Anthony Komaroff, M.D., is professor of medicine and editor-in-chief of Harvard Health Publications at Harvard Medical School. Dr. Komaroff also is senior physician and was formerly director of the Division of General Medicine at Brigham and Women's Hospital. Dr. Komaroff has served on various advisory committees to the federal government, and is an elected Fellow of the American Association for the Advancement of Science.

Question:

Is shingles contagious? If so, how long do I have to stay away from people? I've had the virus for one week.

Answer:

Shingles is contagious, and although you've had shingles for a week, you've had the virus that causes it a lot longer.

Shingles, also called "zoster," is caused by the varicella-zoster virus. Usually, this virus enters our bodies in childhood, when it is the cause of chickenpox. Then the virus stays inside our bodies for the rest of our lives. (Our immune system cannot kill it, so it just tries to keep it quiet.) The virus lives inside nerves that lead to our skin. In most of us, it remains "asleep" inside the nerves, causing no problems. But sometimes, it "wakes up" and begins making copies of itself, and that's when it can cause trouble.

When the virus wakes up, it can cause pain, itching, or a strange unpleasant sensation in a patch of skin. A few days later, that patch of skin starts to develop a rash. The skin turns red. Little blisters form. That's the condition called shingles or zoster. The rash usually lasts just a few days, but sometimes the pain and discomfort can persist.

The virus is present in the blisters on the skin. Other people who were not infected with the virus earlier in life can catch the virus. (This doesn't happen very often.)

When shingles develops, the virus also is often present in that person's saliva, so theoretically it could be transmitted by kissing, but we don't know how often this happens.

My advice to people with shingles is that they cover the shingles with a bandage if they are going to be in close contact with other people. I also advise them to avoid kissing others until the shingles has gone away, although I don't think there is strong evidence that this is necessary.