Cause
Shingles is a
reactivation of the varicella-zoster virus, a type of herpes virus that causes
chickenpox. After you have had chickenpox, the virus
lies inactive in your
nerve roots and remains inactive until, in some
people, it flares up again. When the virus becomes active again, you get
shingles instead of chickenpox.
Anyone who has had even a mild
case of chickenpox can get shingles. People who have a weak
immune system are vulnerable to reactivation of the
virus that causes shingles. Many factors can weaken your immune system,
including aging, injury, and illness. Some medicines slow down the immune
system. For example, medicines that destroy cancer cells (chemotherapy) can interfere with the immune
system.
Transmission
Exposure to shingles will not cause
you to get shingles. But if you have not had chickenpox and you are exposed to
shingles, you can get chickenpox. Someone with shingles can potentially expose
you to chickenpox if you come into contact with the fluid in the shingles rash
blisters.
One study reports that the virus that causes shingles
may be released into the air from shingles sores. Covering the shingles sores
with a type of dressing that absorbs fluids and protects the sore (hydrocolloid
dressing, such as DuoDerm) appears to effectively contain the virus.2