Shingles is caused by a reactivation of the varicella zoster virus, the same virus that causes chicken pox. Shingles is also called zoster and herpes zoster virus. The words "shingles" and "zoster" both translate from different languages into the word "belt," which describes the pattern of the rash of blisters as they appear on the body—generally a band (dermatome) on one side of the body.

Chicken Pox Virus Becomes Active Again

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.

Unfortunately, it isn't yet known exactly what causes the varicella zoster virus to become active again. An important factor, though, is the immune system, which helps keep viruses at bay. Shingles tends to appear when your immune system is weakened. For example, the chances of getting shingles are higher as we get older. But other things can also weaken, or suppress, the immune system's ability to fight infection, such as HIV, anticancer and transplant drugs, stress, and depression.

Is Shingles Contagious?

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.