Chickenpox

Chickenpox and shingles are two diseases caused by the same virus, varicella. The virus is similar to the herpes virus, the roseola virus, and to the Epstein-Barr virus (which causes mononucleosis).

It used to be that most children caught chickenpox as children. The virus is spread by droplets coughed or sneezed out by someone who is already infected. The signs of a chickenpox infection are fever and malaise, 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 thought to be 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.

Shingles is caused when the chickenpox virus (which the body never really gets rid of completely) 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 a single nerve, and the virus usually lies dormant in the nerve root after the initial chickenpox infection). 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, which slows down or stops reproduction of the virus. These treatments are generally given only to people for whom chickenpox is dangerous (cancer patients, immune-compromised people, and adults); in preschool and school-age kids 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. The data we have so far indicates that one dose provides lifelong immunity in about 80-85% of children who receive the vaccine. New 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 3 months after the first dose -- to be sure of developing full immunity. Children who are 13 years old or older, and adults, who have not had chickenpox should 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.