What causes Zoster?
Chicken pox and shingles are actually caused by the same virus known as the Varicella Zoster virus. However there are differences in the way the infection develops and spreads. Also, the chicken pox form of the infection is far more common in children than is the shingles(Zoster or Zona) form.
In chicken pox infections, the virus is spread form one person to another either by direct contact with the actual rash or through the air by coughing or sneezing, just like a cold. Typically within 2 weeks of exposure to chicken pox, the typical pox rash appears initially as a red round or oval spot that develops a "blister-like" center full of yellowish fluid. A child developing chickenpox is considered to be contagious a couple of days before the rash actually breaks out. This is why the disease spreads so easily, as children are contagious before the rash comes out and generally still attend school or daycare. Once the rash appears, the child is contagious for about 3 - 5days, or until all of the blisters have dried or crusted off. Only when all the lesions are crusted can a child return to school or day care.
Shingles..the chicken pox virus returns
For reasons that are not clear, after a chickenpox infection, the varicella virus remains in our bodies forever. The virus remains "asleep" in our nerves. For a variety of reasons, usually in older people or those with weakened immune systems, the virus appears on the skin again. However, this time it only comes out in the area that specific nerve feeds, called a dermatome. It looks like a localized "patch of varicella blisters". This is called Herpes Zoster or shingles.
While we usually see shingles in the elderly, or individuals with weakened immune systems, it can occur in otherwise normal children too, but much less frequently.
Is Zoster contagious?
Importantly, people who have not yet had chicken pox or the varicella vaccination can actually contract the virus and develop typical chicken pox infection from someone who has shingles. More specifically, if they come into contact with the little blisters which actually contain the varicella zoster virus. A person with zoster is considered contagious until the blisters( or vesicles) have dried and crusted. Persons who have had chicken pox in the past or have been vaccinated will be protected, whether they come into contact with active typical chickenpox or shingles.
How is shingles treated?
As with chicken pox, there is no specific treatment for shingles, in otherwise healthy individuals. Specifically, for shingles the main concern is to try to alleviate any related discomfort, pain or itchiness. However in people with weakened immune systems, specific antiviral medications and other treatments may be necessary. Some cases may even require hospitalization.
Now a Zoster vaccine is available for the elderly, that seems to protect against shingles.