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Chickenpox is an infectious disease caused by the varicella-zoster virus, which results in a blister-like rash, itching, tiredness, and fever.
The rash appears first on the trunk and face, but can spread over the entire body causing between 250 to 500 itchy blisters in unvaccinated persons. Prior to use of the varicella vaccine, most cases of chickenpox occurred in persons younger than 15 years of age and the disease had annual cycles, peaking in the spring of each year.
Chickenpox is highly infectious and spreads from person to person by direct contact or through the air from an infected person’s coughing or sneezing or from aerosolization of virus from skin lesions. A person with chickenpox is contagious 1-2 days before the rash appears and until all blisters have formed scabs. It takes from 10-21 days after exposure for someone to develop chickenpox.
In unvaccinated children, chickenpox most commonly causes an illness that lasts about 5-10 days. Children usually miss 5 or 6 days of school or childcare due to their chickenpox and have symptoms such as high fever, severe itching, an uncomfortable rash, and dehydration or headache. In addition, about 1 in 10 unvaccinated children who get the disease will have a complication from chickenpox serious enough to visit a health-care provider. These complications include infected skin lesions, other infections, dehydration from vomiting or diarrhea, or more serious complications such as pneumonia and encephalitis. In vaccinated children, chickenpox illness is typically mild, producing no symptoms at all other than a few red bumps. However, about 25% to 30% of vaccinated children who get the disease will develop illness as serious as unvaccinated children.
Parents can do several things at home to help relieve their child’s chickenpox symptoms. Because scratching the blisters may cause them to become infected, keep your child’s fingernails trimmed short. Calamine lotion and Aveeno® (oatmeal) baths may help relieve some of the itching. Do not use aspirin or aspirin-containing products to relieve your child's fever. The use of aspirin in children with chickenpox has been associated with development of Reye’s syndrome (a severe disease affecting all organs, but most seriously affecting the liver and brain, that may cause death). Use non-aspirin medications such as acetaminophen (e.g., Tylenol®).
Your health-care provider will advise you on treatment options. Acyclovir, famcyclovir, or valacyclovir (medicines that work against herpesviruses) are recommended for persons who are more likely to develop serious disease, including persons with chronic skin or lung disease, otherwise healthy individuals 13 years of age or older, and persons receiving steroid therapy. However, only acyclovir is currently licensed for use in treating varicella.
Varicella vaccine can prevent this disease in most people. Currently, two doses of vaccine are recommended for children, adolescents, and adults. About 15%–20% of people who have received one dose of chickenpox vaccine do still get chickenpox if they are exposed, but their disease is usually mild. In one study, children who received two doses of the chickenpox vaccine were three times less likely to get chickenpox than individuals who have had only one dose.
Shingles, also known as herpes zoster, is a disease caused by the same virus that causes chickenpox. After an attack of chickenpox, the virus lies dormant in the nerve tissue. As we get older (usually over age 50), it is possible for the virus to reappear in the form of shingles.