The varicella zoster virus (VZV) can cause two diseases: chickenpox (varicella) and shingles (herpes zoster). Before a vaccine was developed in 1994, chickenpox was a common contagious childhood disease that produced itchy blisters but rarely caused serious problems. However, if adults who did not have the disease as children contract it, it could cause more serious complications.
Shingles is caused by the same virus that causes chickenpox. Once you have had chickenpox, the varicella-zoster virus lies dormant in your nerves and can re-emerge as shingles. Shingles, which is characterized by a rash of blisters, can be very painful but is not life-threatening. Some people who develop shingles also develop a condition caused postherpetic neuralgia, which causes the skin to remain painful even after the rash is gone. Shingles is most common in people over age 60 or in those with a weak immune system.
The typical rash of chickenpox is made up of groups of small, itchy blisters surrounded by inflamed skin. The rash usually starts on the face, scalp, or chest, quickly spreading throughout the body. It usually appears a few days after the individual has been exposed. Over 4 days, each blister tends to dry out and form a scab, which then falls off 9 - 13 days later.
The rash is usually preceded or accompanied by:
The typical shingles rash starts as redness followed by blisters that usually cover only one side of the body. The rash follows the path of the nerve where the virus has lain dormant. About 50 - 60% of people with shingles have the rash on their trunk. The next most common site is one side of the face, which may even include the tongue, eye, or ear.
Before the rash appears, the infected individual will have warning symptoms of pain -- usually a sharp, aching, piercing, tearing, or burning sensation -- on the part of the body where the rash appears 1 - 5 days later. That area may also feel itchy, numb, and unbearably sensitive to touch, even just from clothes touching the skin.
Other symptoms may include:
A physician can usually diagnose chickenpox easily because of its characteristic rash. If there is any doubt, however, the doctor may view a scraping from one of the blisters under the microscope.
For cases of shingles, a physician can usually make a diagnosis from the history of pain and other symptoms and the rash itself. He or she may take a scraping from one of the blisters for a laboratory test.
Source: Varicella-zoster virus http://www.umm.edu/altmed/articles/varicella-zoster-000080.htm#ixzz2UceMGGEM
Both chickenpox and shingles are caused by the varicella-zoster virus (VZV), a type of herpes virus. The virus is spread when you come in contact with the rash or by sneezing, coughing, and breathing -- in other words, when someone with chickenpox sneezes or coughs, there are droplets with the VZV virus in the air. The person is contagious from 2 days before the rash appears until all of the blisters have crusted over.
While shingles is caused by the same virus that leads to chickenpox, the way you develop this painful skin condition is different. After you have had chickenpox, the virus lives in a dormant state, as if it is hibernating, in nerve cells along your spine. Later in life, when it "wakes up" -- usually from a weakened immune system, aging, or other risk factor -- the virus travels down the path of the particular nerve where it was "hibernating," causing pain followed by the rash. Anyone who has had chickenpox can get shingles, although a vaccine can reduce your risk.