The varicella zoster virus, which causes shingles and chickenpox, spreads through direct contact with the rash when it is in the blister phase. It does not spread before blisters form or after they form a crust, according to MedlinePlus. Keeping blisters covered helps to prevent spreading the virus.
The varicella zoster virus can only spread to a person who has never had chickenpox. If the virus infects a person, he develops chickenpox and not shingles, according to MedlinePlus. Once the body heals from the chickenpox, the virus remains dormant. Anyone who has had chickenpox has the potential to develop shingles; however, most with the condition are age 50 or older.
The risk for developing shingles increases with age, according to MedlinePlus. Disease, a weakened immune system or medications that depress the immune system, increase the chances of developing the disease.
In the United States, approximately 1 million people develop shingles each year. A person typically only has shingles once in a lifetime, although in rare instances, it is possible to have the disease two or three times, according to MedlinePlus. Medication is available for shingles, and doctor's prescribe it once the rash develops. The medication helps to reduce the length and severity of the illness