Shingles is an infection caused by the varicella zoster virus, the same infection that causes chicken pox. The main difference, however, is that shingles generally erupts in a band on one side of the body, rather than all over your body.

After the chicken pox blisters have healed, the varicella zoster virus lies dormant (inactive) in neurons (nerve cells) next to your spinal cord, sometimes for decades. When the virus becomes active again, it travels down the nerve fibers that extend to your skin, and a rash develops.

Who Is at Risk?

Anyone who has had chicken pox is at risk of developing shingles. More than 90% of Americans over age 15 have had chicken pox. Although young people can get shingles, this disease usually occurs in people over age 50. The frequency of shingles is basically constant between the ages of 20 and 50 years (2.5 cases per 1,000 people per year). The chances of getting shingles then doubles in people between ages 50 and 60 years, and then doubles again in people age 80 to 90 years.

An important factor, though, is the immune system, which helps keep viruses at bay. The varicella zoster virus can become active again because of a decrease in a person's immunity to the virus. This decrease in immunity can occur with advanced age. However, sometimes it is not known why the virus becomes active again.

The following may cause the varicella zoster virus to become active and cause an outbreak of shingles:

• Diseases that affect the immune system (eg, non-Hodgkin's lymphoma and HIV)
• Anticancer and immunosuppression drugs that suppress the immune system (eg, chemotherapy)
• Temporary depression of the immune system from a cold or sunburn
• Stress (due to negative life events)
• Major depression

Shingles in Children

Children whose mothers developed chicken pox within 5 to 21 days before giving birth are susceptible to developing shingles. These babies are usually born with chicken pox or develop it within a few days of birth. One-third of these children develop shingles during the first 5 years of their life.

Can I Get Shingles Again?

Most people who get shingles develop immunity to the varicella zoster virus and will not get it again. Only about 4% of people will have another outbreak in the future. When shingles does recur, it is often in people with a compromised immune system (eg, they are infected with HIV or are undergoing chemotherapy treatments). A second outbreak of shingles may occur many years after the first outbreak. When shingles does recur, the rash usually does not appear in the same location as the first outbreak.

Can I Catch Shingles?

You cannot catch shingles from someone who has it. However, the rash that occurs with shingles sheds the same varicella zoster virus that causes chicken pox and may be contagious. So, if you have not had chicken pox or have not been vaccinated against the varicella zoster virus, you can develop chicken pox (not shingles) if you come in contact with someone who has shingles. People with shingles can transmit the virus only if the blisters have broken and the virus is transmitted when skin-to-skin contact with broken blisters occurs.