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Chicken Pox is caused by varicella zoster virus, one of seven human herpes viruses. It is transmitted via virus in water droplets in exhaled air of an infected individual infecting the next person via the conjunctivae (lining of the eye) or the respiratory tract. Once exposed, it may take 10 to 21 days to develop the characteristic rash, however the person is definitely contagious 1 to 2 days, and possibly up to 4 days, prior to the development of the rash. This is why it is so hard to control an outbreak of chicken pox.
Classic symptoms of varicella include the development of an itchy rash that starts off as a flat red spot, which progresses to a bump (papule), which then becomes fluid filled (vesicle). The fluid inside the vesicle becomes cloudy and filled with pus, then it breaks open and scabs over. The key to diagnosing varicella is that there are several "crops" of lesions over the first several days of illness, so that the lesions are all in different stages of that cycle. It is usually associated with fevers up to 102, and in unvaccinated children, lesions may number 200 to 300. Typically, children are not allowed to return to school until all lesions have crusted over. Children younger than one year or teenagers and young adults have more serious illness, with possible development of varicella cellluitis (a secondary infection of the skin), pneumonia, meningitis, hepatitis, arthritis, kidney involvement, or testicular involvement. Prior to the development of the varicella vaccine, approximately 100 people died each year in the U.S. from chicken pox, and about 12,000 people were hospitalized due to complications.
If a pregnant woman contracts chicken pox in the first 20 weeks of her pregnancy, the most common problems experienced by the fetus is abnormal development of the extremities. However, there is also possible development of vision problems such as cataracts, brain calcifications, small brain size, or the development of fluid around the brain (hydrocephalus).
It is possible to contract varicella despite being vaccinated, and if it occurs, the diagnosis can be much more challenging. This "break through" rate of chicken pox is estimated to occur in approximately 15% of vaccinated children and is the reason that a "booster dose" of varicella vaccine is now being recommended by the American Academy of Pediatrics. In vaccinated children, the illness is very mild, usually involving only a handful of lesions and usually no fever. It is common for it to be mistaken for bug bites. The good news is that vaccinated children do not develop the varicella pneumonia or varicella meningitis type complications that can sometimes develop in the unvaccinated child.
Zoster:
Zoster is also known as Shingles and it is a re-activation of the Varicella zoster virus which has been living in the nerve roots. It causes vesicles which look very similar to those of chicken pox, but since it is only affecting the area supplied by the nerve root containing the virus, the rash is limited to one area of the body. In children, this is most often seen on arms, hands, legs or the groin of affected children, and in adults, the lower chest or lumbar areas. It is unusual in children and is seen more commonly in children with immune problems, such as cancer.
Treatment:
Fevers associated with chicken pox should be managed with acetominophen or ibuprofen, not aspirin, as aspirin has been known to cause Reye syndrome ( neurologic deterioration). Calamine lotion and oral Benadryl can be used to control itching, but do not combine Caladryl with oral Benadryl since Caladryl contains benadryl and it is theoretically possible to overdose on Benadryl this way, especially in the younger children and infants. We do recommend keeping nails trimmed short and checking the skin regularly for areas that seem to be getting redder or oozing more than the others. This might indicate a secondary infection. Likewise, notify us if any area becomes painful because occasionally children develop abscesses in the muscle underlying the skin lesions. In children with severe illness or underlying health problems, acyclovir (an oral anti-viral medicine) may be prescribed.
Prevention:
The most effective way to prevent varicella is by being vaccinated. The varicella vaccine is routinely given at age 1 year and there is a new recommendation to give children a booster dose of the vaccine between age 4 and 6 years of age. If the child is older than 13 years when they receive the first dose of vaccine, two doses is also recommended. The side effects of the vaccine include soreness or swelling where the shot was given, fever in 10% of people, mild rash up to a month after vaccination. Seizures due to fever have been documented in less than 1 out of 1000 people. Pneumonia has been reported but is very rare. There have been rare reports of low blood counts and severe brain reactions after vaccination with varicella, but it has happened so rarely it is not clear if it was related to the vaccine or not. If it is, it is extremely rare. You should not receive the varicella vaccine if you are pregnant, have HIV/AIDS, cancer or undergoing therapy with any drug that affects the immune system such as steroids, cancer medications or radiation. You should also not receive the vaccine if you are allergic to gelatin, the antibiotic Neomycin, or have had a prior allergic reaction.