Chickenpox and shingles are two diseases caused by the same virus, varicella zoster virus or VZV. The virus is similar to the herpes virus, the roseola virus, and to the Epstein-Barr virus (which causes mononucleosis).
Until the late 1990's, most children caught chickenpox as children. VZV is spread by droplets coughed or sneezed out by someone who is already infected. The signs of a chickenpox infection are fever and malaise (feeling lousy), followed by the typical rash. The "poxes" start as small red spots, which become red bumps and then develop a small "vesicle", or bubble of clear fluid, in the middle. Eventually the vesicle breaks, the "pox" crusts over, dries, and then falls off. The rash usually appears first on the head (often along the hairline), then spreads over the entire body in successive "crops" of new "poxes". An infected child is regarded as contagious from 1-4 days before the rash appears until all of the "poxes" have crusted over. There is some evidence that a child is no longer contagious 6 days after the rash starts, but most people will wait until all of the "poxes" are crusted just to be safe.
In toddlers and school-age kids, the fever, malaise, and rash are usually all there is to chickenpox. One exception to this is bacterial "superinfection" of a "pox", which can be treated with antibiotic ointment or oral antibiotics. In infants and older people (late teens and up), and in people with immune-system problems (such as cancer patients, but also including people taking lots of steroids for asthma, eczema, or other diseases) chickenpox can be much more serious, and sometimes fatal. The complications can include chickenpox-viral pneumonia, as well as damage to other organs. However, these complications are extremely rare in preteen and early-teen children.
Your body never gets rid of VZV completely. The virus usually lies dormant in the nerve root after the initial chickenpox infection, after it "splices" its DNA into the DNA of the nerve cell. Shingles is caused when the VZV is reactivated after many years. The rash of shingles is usually limited to a strip of skin somewhere on the body (the strip is the area of skin covered by the nerve in which the VZV lies dormant). The rash often looks similar to the original chickenpox rash, but it can be very painful; some patients need narcotic pain medicines to relieve the pain of shingles. People who have shingles are contagious (someone who has not had chickenpox can get chickenpox after exposure to a person with shingles), but they are less contagious than\ patients with full-blown chickenpox.
Chickenpox can be treated with immune globulin, which provides passive immunity, and with acyclovir or similar medicines which slow down or stop reproduction of the virus. These treatments are generally given only to people for whom chickenpox is dangerous, such as cancer patients, immune-compromised people, and adults. In preschool and school-age children chickenpox is fairly benign and treatment is often not warranted -- and may prevent development of full immunity, leaving the child vulnerable to a more serious infection as an adult.
There is a vaccine available for chickenpox. One dose provides lifelong immunity in about 80-85% of children who receive the vaccine. Evidence published in the New England Journal of Medicine in March, 2007 indicates that the immunity from a single dose of vaccine may wear off with time. We now recommend that children age 1-12 years receive two doses -- one at age 1 year, and one at least 3 months after the first dose -- to be sure of developing full immunity. Generally we give the second dose with the rest of the standard kindergarten vaccinations at age 4-5 years. People who are 13 years old or older who have not had chickenpox need receive two doses of vaccine at least 4 weeks apart. The vaccine is required by most American states for school entry. A combination vaccine, called "MMRV", contains both the chickenpox vaccine and the vaccines against measles, mumps, and rubella (German measles), and protects against all four diseases with fewer needle pokes. Although having natural chickenpox definitely confers lifetime immunity, as more and more children are vaccinated against chickenpox it is becoming more and more difficult to contract the natural disease. Therefore, I encourage parents of younger children to receive the vaccine. As chickenpox vaccination becomes more commonplace, it may be possible to eliminate chickenpox as we have eliminated smallpox and may soon eliminate polio -- but eliminating chickenpox won't happen without universal vaccination.
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