According to the University of Maryland Medical Center, there are about 500,000 cases of shingles, or herpes zoster, in the United States every year. Shingles is a viral infection that is caused by the varicella-zoster virus, the same virus that causes chickenpox.
After a person has had chickenpox, the virus remains dormant in the body, in nerve tissue near the spinal cord and brain. It may reappear at any time in the form of shingles---or never, depending on the person's health. During an outbreak, only those who have not had chickenpox before are susceptible. Shingles are infectious until all blisters have crusted over. If someone becomes infected by exposure to shingles, symptoms will appear in 14 to 21 days in the form of chickenpox.
The symptoms of shingles often begin as pain or a burning sensation that affects a small area on one side of the body. This may be followed by a red rash four or five days later and then the appearance of fluid-filled blisters that break open and crust over, causing severe itching.
The exact cause of an outbreak of shingles is unclear. It is more common in older people and those with weakened immune systems. Since it is caused by a reactivation of a latent virus, shingles has no incubation period.
Some people experience complications from shingles that may include postherpetic neuralgia, or continued pain after the blisters have cleared; vision loss that may result from shingles in and around the eye; and in more severe cases, encephalitis, hearing or balance problems, or facial paralysis.
Though a shingles outbreak usually heals on its own within a few weeks, some physicians will prescribe antiviral drugs and pain medication to ease pain, speed healing and help prevent complications.
According to the Mayo Clinic, two vaccines may help prevent shingles or lessen the severity. The varicella vaccine is routinely given to children and adults who have never had chickenpox, and the varicella-zoster vaccine is given to people over the age of 60 who have had chickenpox and run the risk of getting shingles.