Shingles, also called herpes zoster, is an infection caused by the varicella zoster virus (VZV), the same virus that causes chickenpox. It can cause nerve inflammation and intense pain, a reddened rash, and blisters (vesicles) that break open and crust over before slowly resolving. In most cases, the rash and pain subside within a few weeks, but some of those affected may have severe pain that lingers for months or even years.
When someone is first exposed to VZV, usually in childhood, the person develops chickenpox, a common, highly contagious, primary systemic infection that causes multiple "crops" of vesicles in multiple locations on the body. Chickenpox is passed from person to person through direct contact with fluid from the blisters or coughing or sneezing. Once the chickenpox has resolved, the virus becomes dormant, persisting in a latent form at the base of sensory nerve cells near the spinal cord and brain. Normally, the body's immune system maintains this latency and produces sufficient VZV antibodies to protect against future exposures.
The virus can re-activate and cause shingles in people with:
- Medical conditions such as certain cancers or HIV/AIDS that compromise the immune system
- Immunosuppressive drug treatments given after an organ transplant
- A decline in immunity due to aging
The virus begins to reproduce again and moves outward along the length of one or more sensory nerves to the surface of the skin. This can cause symptoms associated with shingles, including a ribbon or band of lesions on one side of the trunk, face, or arm corresponding to the section of skin (dermatome) that the affected nerve serves.
The virus that causes shingles may be passed to other people through contact with an open vesicle. The people who are exposed will only become infected if they have not been previously exposed to a VZV infection or have not been vaccinated – and will develop chickenpox, not shingles.
Almost one out of three people in the United States will develop shingles during their lifetime. Nearly 1 million Americans are affected each year. About half of those cases occur in people who are over the age of 60.
Although most people will only have shingles once, the virus can potentially re-activate and cause shingles again. Those with weakened immune systems may have difficulty regaining and maintaining virus latency. A baby who is born with chickenpox is at an increased risk for developing pediatric shingles. This is a rare event that sometimes occurs when a woman has chickenpox, or – even more rarely – develops shingles, during her pregnancy.