What is shingles?
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.
Later in life, typically decades later, with increasing age and associated natural decline in immunity, and/or when a person's immune system becomes weakened such as with HIV/AIDS, certain cancers and their treatments, or with immunosuppressive drugs given after an organ transplant, the virus can re-activate and cause shingles. VZV 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.
Shingles is less contagious than chickenpox, but the virus may be passed to another person through contact with an open vesicle. The person exposed will only become infected if he or she has not been previously exposed to a VZV infection or has not been vaccinated – and will develop chickenpox, not shingles.
Almost all adults in the U.S. have had chickenpox and about one million people a year get shingles in this country. It is most common in those over 60 years of age and in those with weakened immune systems. It is estimated that 50% of Americans will get shingles by the time they are 80 years old.
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.