What is it?
Shingles is an infection caused by the same virus that causes chickenpox (varicella zoster virus, which is a type of herpes virus). You can not develop shingles unless you have had a previous infection of chickenpox (usually as a child). The shingles may occur in people with suppressed immune system, including people with HIV and those over the age of 60 (especially those having diabetes, cancer, or other disease that may suppress immunity).
More than 90% of people in the United States have antibodies against varicella-zoster virus and many develop chickenpox at some point in their lives, usually when they are school children. Despite the chickenpox lesions heal the virus does not die - he continues to live quietly in nerve cells near the spine. Since the immune system can not kill the virus completely, it can prevent the virus becomes active again, usually for life of the infected person. However, if the immune system becomes suppressed, the virus can escape the nerve roots and become active. Instead of coming back as chickenpox (varicella), he returns as shingles (zoster).
When shingles occurs, it affects only one side of the body, usually in the form of a strip-shaped belt along a single line of nerves. The most common areas are the back, upper abdomen or face. It can also affect the eyes and more rarely the inner ear. Shingles can be very painful, but can be treated.
You may not transmit shingles to someone who has had chickenpox in the past or has been vaccinated against varicella-zoster virus. However, the rash can "accommodate" the varicella-zoster virus. Someone who has not had chickenpox or have not been vaccinated against the virus can develop chickenpox if they come into contact with the shingles eruptions.
Approximately 3% to 5% of people infected with the varicella-zoster virus will suffer from shingles at some point in their lives, most of them after 50 years. The shingles are from 15 to 25 times more prone to occur in HIV-positive people, regardless of their CD4 cell count. In other words, the CD4 cell count need not be low for the person to be at risk; the disease can develop even when the immune system seems relatively healthy. In HIV-positive people with significant suppression of the immune system (CD4 cell count below 50), there is an increased risk of zoster infection in other parts of the body, including the retina in the fundus of the eye. This can result in rapid blindness.