Shingles, also known as herpes zoster, is a painful rash caused by the varicella-zoster virus (VZV). The varicella-zoster virus also causes chickenpox.
Chickenpox is an infectious disease mainly seen in childhood, associated with a fever, rash, and skin blisters. After a person recovers from chickenpox and is no longer ill, the body never completely rids itself of the virus. Instead, VZV remains present in an inactive (dormant) state in dorsal root ganglia, the part of the spinal nerves responsible for sensations such as pain. Years after an episode of chickenpox, VZV can become reactivated, causing shingles. Typically, shingles appears as a painful rash along a band of skin (dermatome) supplied by a single nerve root.
Most cases of shingles occur in people over the age of 50. Approximately a third of the population in the United States will experience shingles during their lifetime. Shingles is not a life-threatening condition, but it is extremely painful.
Only individuals who have experienced chickenpox or received the chickenpox vaccine can develop shingles. It is unclear what triggers dormant VZV to reactivate and cause shingles in some people and not in others. Older people and individuals with suppressed immune systems or cancer have a higher risk of developing this condition.
Shingles usually causes a band of blisters, affecting one side of the trunk or face. Typically, the condition affects one or two thoracic dermatomes and is called localized herpes zoster. However, individuals with weakened immune systems may develop disseminated zoster, a type of shingles that spreads across large areas of the body.
Pain is the primary symptom of herpes zoster. Often, there is excruciating pain described as burning, aching, or stabbing. Other symptoms may include itching, numbness, and tingling of the skin. A few days after the onset of pain, the rash will appear. Next, clear fluid-filled blisters (vesicles) develop along the affected dermatome. Over a period of two to four weeks, the vesicles break open, crust over, and heal, but often the affected skin is left darkened and scarred.
Older individuals and people with a weakened immune system are more likely to experience severe forms of shingles and more complications from the infection.
The virus associated with shingles is very contagious. Direct contact with active blisters can spread the infection to susceptible people (those who have never experienced chickenpox). When the virus from shingles infects others, it causes chickenpox, not shingles.
After the lesions dry and crust over, there is no longer a risk of spreading the infection to other people. While contagious, a person with shingles should avoid contact with pregnant women, newborns, and people with impaired immune systems, because chickenpox infections may cause serious complications in these individuals.
Most cases of shingles are diagnosed by the patient’s symptoms and physical examination, revealing a painful rash with blisters on one side of the body. The diagnosis can be verified by scraping the skin lesions to identify the virus in a laboratory.
The chickenpox vaccine (Varivax®) is given to reduce a person’s chance of experiencing chickenpox. It does not provide a guarantee against developing the infection, but it often lessens the severity of the illness. Children who have received the chickenpox vaccine have a significantly lower risk of developing shingles than people who have experienced a chickenpox infection.
The shingles vaccine (Zostavax®) is recommended for adults over age 60 to prevent reactivation of VZV and shingles. The shingles vaccine is not effective for everyone and some patients develop shingles despite having received the vaccine, but their illness is usually milder with fewer complications, such as postherpetic neuralgia.