Chicken Pox

Chicken Pox, also called varicella, highly contagious viral disease that affects mainly children. Prior to the approval of a vaccine in 1995, more than 4 million people in the United States developed chicken pox each year, and about 100 of those infected died. Although rare, deaths from the disease still occur.

Typically, chicken pox begins with a low fever, headache, rash, and a general feeling of sickness, or malaise. The rash, which usually covers the face, scalp, and trunk of the body, starts as red bumps but quickly develops into small blisters. The rash and the blisters are extremely itchy. As the disease progresses, the blisters break open and form scabs, which fall off after about one to two weeks. The incubation period—the time between initial infection and the first appearance of symptoms—is approximately two weeks.

Chicken pox is caused by varicella-zoster virus, a type of herpes virus. The virus spreads through the air via infected droplets emitted from the nose or mouth while coughing or sneezing. Touching the fluid from a chicken pox blister can also spread the disease. Chicken pox is contagious for approximately seven days during a person’s period of infection. Contagiousness begins about two days before symptoms appear and continues until all blisters have formed scabs. Doctors recommend keeping the infected person isolated from others during those seven days.

Chicken pox is usually much milder in children, for whom hospitalization is usually not required, than it is in adults. However, in children whose immune systems are weakened from such diseases as cancer or acquired immunodeficiency syndrome (AIDS), the disease can be severe.

Contracting chicken pox provides immunity, or lifelong resistance, against the disease. However, after the symptoms disappear, the virus remains in the body's nerve cells and occasionally reactivates later in life, causing a disease known as shingles, an infection of the nerve fibers. Shingles usually occurs in people over 50, due to an age-related weakening of the immune system, and causes pain, burning, itching, inflammation, and blisters.

Treatment of chicken pox is usually limited to bed rest, acetaminophen for relief of fever and discomfort, and measures that soothe the itching, including lukewarm baths and application of topical medicines such as calamine lotion. Excessive scratching can cause infection of blisters, which can lead to scarring. Acyclovir, an antiviral drug, can be used to treat severe cases of chicken pox, particularly in patients with a weakened immune system.

A child or adolescent with chicken pox should never be given aspirin or other salicylates because of the possible link to Reye's syndrome, a disease that develops only after a viral infection, characterized by high fever, vomiting, liver dysfunction, and swelling of the brain. Although Reye's syndrome is rare, it is life threatening.

In 1995 the United States Food and Drug Administration (FDA) approved the first vaccine for chicken pox for use in healthy children 12 months and older, as well as in adolescents and adults not yet exposed to the disease. From 1995 to 2004, the number of cases of chicken pox fell by more than 80 percent. Of children between the ages of 12 months and 12 years, 97 percent develop immunity to the disease after one dose of the vaccine. Of older adults and children, 78 percent develop immunity after one dose of the vaccine and 99 percent after two doses.