Shingles
Shingles (herpes zoster) is infection with the varicella-zoster virus that produces a severely painful skin eruption of fluid-filled blisters.
Chickenpox and shingles are caused by the varicella-zoster virus. Chickenpox is the initial infection with varicella-zoster virus (see Section 23, Chapter 273), and shingles is a reemergence of the virus, usually years later. During the chickenpox infection, the virus spreads in the bloodstream and infects many nerve cells (ganglia) of the spinal or cranial nerves, remaining there in a dormant (latent) state. The virus may never cause symptoms again, or it may reactivate many years later. When it reactivates, the virus travels back down the nerve fibers to the skin, where it creates painful sores resembling those of chickenpox. This outbreak of sores (shingles) is almost always limited to a strip of the skin on one side of the body that contains a group of infected nerve fibers. This area is called a dermatome (see Section 6, Chapter 93). Unlike HSV infections, there is usually only one outbreak of shingles in a person's lifetime.
Shingles may develop at any age but is most common after age 50. Most often, the reason for reactivation is unknown, although reactivation sometimes occurs when the body's immunity is reduced by another disorder, such as AIDS or Hodgkin's disease, or by use of drugs that impair the immune system. However, the occurrence of shingles does not usually mean that the person has another serious disease.
Symptoms and Complications
Some people with shingles feel unwell and have chills, a fever, nausea, diarrhea, or difficulties with urination in the 3 or 4 days before shingles develops. Others experience pain, a tingling sensation, or itching in an area of skin. Clusters of small, fluid-filled blisters surrounded by a small red area then develop. The blisters occupy only the limited area of skin served by the infected nerves. Most often, blisters appear on the trunk, usually on only one side. However, a few blisters may appear elsewhere as well. The involved area of the body is usually sensitive to any stimulus, including light touch, and may be severely painful. Children with shingles usually have less severe symptoms than adults.
The blisters begin to dry and scab about 5 days after they appear. Until scabbing occurs, the blisters contain varicella-zoster virus, which can cause chickenpox if transmitted to susceptible people. Blisters that cover large areas of skin or persist for more than 2 weeks usually indicate that the immune system is not functioning properly.
One attack of shingles usually gives a person lifelong immunity from further attacks; fewer than 5% of people have further attacks. Scarring of the skin, which can be extensive, may occur, but most people recover without any lasting effects.
A few people, more commonly older people, continue to have chronic pain in the area (postherpetic neuralgia). Involvement of the part of the facial nerve leading to the eye can be quite serious, and if it is not treated properly, vision may be affected.
 See the sidebar What Is Postherpetic Neuralgia?
Diagnosis
A doctor may have trouble diagnosing shingles before the blisters appear, but the location of the initial pain in a vague band on one side of the body can be a useful clue. Depending on the nerves involved, the pain may resemble that caused by appendicitis, a kidney stone or gallstone, or inflammation of the large intestine. However, once the blisters appear in the typical pattern following a nerve root, the diagnosis is usually clear. Laboratory tests are seldom performed but may be used to confirm the diagnosis.
Treatment
There are several effective antiviral drugs for shingles. Oral antiviral drugs such as famciclovir, valacyclovir, and acyclovir are often given, particularly to older people and to those with an impaired immune system. These drugs do not cure the disease, but they can help relieve the symptoms and shorten the duration of illness. There is also evidence that taking corticosteroids along with these drugs may help. To prevent secondary bacterial infections, the skin should be kept clean and dry.
Pain-relieving drugs are often required. Nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen may be tried, but oral opioids are often necessary (see Section 6, Chapter 78).
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