What causes shingles?
Shingles is caused by the varicella zoster virus, which also causes chickenpox. If you have had chickenpox, the varicella virus remains in a group of nerves in your central nervous system, but doesn't cause any symptoms. This is called a dormant virus. The central nervous system consists of the brain and spinal cord, which are connected to the nerves in the body. When the virus becomes active again, it causes the symptoms of shingles. No one is sure why the virus becomes
active. However, it seems to be linked to a weakened immune system, such as in people who are ill (such as with cancer or HIV), have had major surgery, or are taking immunosuppressant medications or drugs with cortisone.
Varicella zoster virus, the same virus that causes chicken pox, causes shingles. This virus is in the herpes family. Shingles is also called herpes zoster. Although caused by the same virus that causes chickenpox, shingles does not occur in the same way. Shingles, unlike chickenpox, cannot be spread through the air from an affected individual to another person. Only individuals who have had chickenpox can develop shingles, which results when the dormant chickenpox virus in the individual's nervous system is reactivated.
Individuals with shingles should nonetheless take care when in close contact with others. That is because shingles blisters on the skin contain the live varicella zoster virus. If the blisters are broken, the live virus can be passed to another person through direct skin-to-skin contact. Individuals exposed to the virus in this way who have not had chickenpox or have not received the chickenpox vaccine can develop chickenpox.
Any weakening of the body's immune system can cause the varicella zoster virus to "reawaken" and appear in adulthood as shingles, although the exact reasons are not entirely understood. The immune system can be weakened by aging; sunburn; use of steroids; illnesses such as cancer, HIV/AIDS, and colds; certain medical treatments - for example, chemotherapy and radiation therapy; periods of increased stress; and excessive alcohol intake.
Shingles is not a new infection; rather, it is a second outbreak of the chicken pox virus. Some of the virus germs that cause chicken pox stay in the body, remaining inactive in the nerve cells near the spine for many years. Then the herpes zoster virus suddenly wakes up from the dormant state and grows. Once active, the germs travel along the nerve paths to the skin, leaving a path of destruction along the nerves in which they travel. The result is the pain and rash of shingles.