What are shingles?
Shingles results from the same virus (varicella zoster) that causes chickenpox. All individuals who have had chickenpox are at risk for shingles. The disease most commonly affects those over fifty, but can develop at any age. After initial manifestations of chickenpox, the virus remains dormant in sensory dorsal root ganglia. Each dorsal root receives sensation from a strip of skin on only one side of the body in a particular distribution called dermatome (map of the skin). Shingles outbreaks occur most commonly on the back, along the distribution of a single dermatome wrapping around one side to the chest or abdomen. They may travel from the upper back to the arm or from the lower back to the leg. Shingles can also occur on the face and, in rare cases, can involve the optic nerve of the eye.
The virus can stay inactive in the nerve root for decades. It is reactivated by stress, illness, decreases in immune function, or aging. The first symptom is often a sensation of tingling, burning, or sharp pain over the skin area supplied by the affected nerve root. Within several days, a rash appears, characterized by a cluster of blisters with surrounding redness spreading along the dermatomal pattern. The rash typically does not cross the midline. The blisters scab over in about three days and clear within several weeks. Until the blisters are completely scabbed over, the fluid within the blisters can be contagious via contact. Shingles cannot be acquired from contact exposure, but people who have never had chickenpox can develop chickenpox following exposure to the shingles rash.
The fluid within the blister may be sampled for viral culture to obtain an accurate diagnosis. The diagnosis can usually be made clinically by the characteristic rash. In rare cases, generally in the elderly, nerve pain may persist for months to years after disappearance of the rash, a condition called postherpetic neuralgia.
If shingles is diagnosed within three days of appearance of the rash, then antiviral medications (acyclovir, famciclovir, or valacyclovir) can be used to stop viral replication and help to shorten the course of the illness. Treatment also involves pain control with local cool compresses, anti-inflammatory medications, or even mild narcotics. Gabapentin, a drug similar in structure to an inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), is useful against pain experienced in postherpetic neuralgia.
In 1995, the chickenpox vaccine was approved for use in the United States; individuals who are vaccinated against chickenpox will not contract chickenpox and, thus, will never be at risk for developing shingles. In 2006, Zostavax (zoster vaccine live) was approved for use in the United States to reduce the risk of shingles in older adults. The vaccine is only a preventive measure and does not treat ongoing shingles.
The association between chickenpox and shingles was first made in 1888. The virus belongs to a family of viruses called herpes, which is derived from the Greek word herpein, meaning “to creep.”
Because more than 90 percent of adults in the United States harbor the varicella zoster virus, diseases caused by the virus remain significant clinical problems, particularly in the elderly and those with compromised immune systems. Although vaccination, antiviral therapy, and symptomatic therapies provide effective prevention and treatment to many patients, further research on the varicella virus and improved therapies continues.
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