Chickenpox is a very common and highly contagious disease. Although the symptoms can be annoying and uncomfortable and limit normal activities, the disease is usually mild and rarely serious. In otherwise healthy children, chickenpox lasts two weeks or less and does not cause complications. In adults, newborn babies, and children with weakened immune systems, however, it can be a serious, long-lasting disease.

Chickenpox is caused by a type of herpesvirus called varicella-zoster virus (VZV). After the initial chickenpox infection, VZV hides in nerve cells and is sometimes reactivated later in life. This reactivated, often very painful, disease is called herpes zoster or shingles. Researchers are trying to learn what causes the virus to become active again after being dormant for many years.

Chickenpox epidemics can occur anytime of the year, but are most common in late winter and early spring. Doctors estimate that each year 3.5 to 4 million people, mostly children, get chickenpox. Ninety percent of cases are in people under 15 years of age. The U.S. Centers for Disease Control and Prevention (CDC) reports that there are approximately 100 deaths and 9,300 hospitalizations due to the complications of chickenpox each year. A vaccine to prevent chickenpox became available in 1995. The numbers of cases should decline as more people get immunized with this vaccine.

Symptoms and Diagnosis

The most common signs and symptoms of chickenpox include a rash, fever, tiredness, and loss of appetite. The fever begins a day or two before the rash in about half of patients and is usually less than 101.5°F, but may be as high as 106°F. The rash consists of many (usually less than 300) fluid-filled vesicles surrounded by red sores. Although the rash can involve the entire body, it typically is found on the back, chest, face, and abdomen. The effects of the rash may be mild and barely noticeable or severe and accompanied by intense itching. As the disease spreads from child to child within a family, the intensity and extent of the rash may increase.

A doctor can easily diagnose chickenpox by examining the characteristic rash, with healed and unhealed sores on the body, and by noting the presence of other symptoms mentioned above.

Transmission

It is virtually impossible for a susceptible person to avoid getting chickenpox. It is highly contagious and spreads quickly in settings like day-care facilities and schools and within families. The virus is transmitted by direct contact with the rash on an infected person or by droplets dispersed into the air by coughing or sneezing.

The time between exposure to the virus and the development of symptoms is usually about two weeks, but can range from 10 to 21 days. A person can transmit the disease for up to 48 hours before the telltale rash of chickenpox appears. The period of transmission lasts for four to five days after the rash begins until the sores have crusted over. Therefore, staying away from someone only after they have visible signs of chickenpox is probably too late to prevent transmission.

Rarely, a susceptible person can get chickenpox from someone who has a reactivated VZV infection (shingles).

Treatment

Unless the infection is severe, children with chickenpox usually are not treated.

Scratching can make the lesions harder to heal, cause scarring and increase the risk of bacterial skin infections. The doctor may recommend anti-itch drugs, such as over-the-counter antihistamines, to control this troublesome symptom. Warm baths with uncooked oatmeal or cornstarch added also can help relieve the itching. Fingernails should be kept clean and cut short.

Fever can be reduced with acetaminophen. Aspirin should not be taken by anyone with chickenpox because it can lead to a serious disease called Reye's syndrome. Cool baths also can help bring down a fever.

Acyclovir (Zovirax(r)) is an antiviral drug that attacks the virus. When treatment is started very soon after the first sores appear, it shortens the duration of rash formation by about one day and reduces the number of new sores. The American Academy of Pediatrics recommends it for use in premature babies, adolescents, adults, and other high-risk populations.

Complications

Because chickenpox most often is an uncomplicated infection, it ordinarily does not require a visit to the doctor.

It is wise, however, to visit a doctor if symptoms other than the rash, low fever, and fatigue are present. Symptoms that require immediate medical attention are fever of more than 103°F, dizziness, rapid heartbeat, shortness of breath, tremors, loss of muscle coordination, vomiting, and/or stiff neck.

If the lesions become infected with bacteria such as staphylococcus or streptococcus, a doctor can prescribe an appropriate antibiotic.

In children and adults whose immune systems are impaired by disease or suppressed by drugs (including steroids), chickenpox can affect internal organs. Also, people with impaired immune systems are more likely to develop bacterial skin infections, and their sores take longer to heal. In children with leukemia, chickenpox can be life-threatening.

Infrequently, chickenpox can cause central nervous system complications of which the most serious is encephalitis (inflammation of the brain). Encephalitis can be life-threatening in adults and usually lasts for a minimum of two weeks. Of those patients who survive, 15 percent continue to have neurologic symptoms after the initial infection has cleared. Other nervous system complications include meningitis and Reye's syndrome.

Another serious complication, which occurs mainly in adults, is varicella pneumonitis (inflammation of the lungs). This complication can be life-threatening to women during the second or third trimester of pregnancy.

If a pregnant woman develops chickenpox five days before or up to 48 hours after delivery, the baby can be born with complications from the infection. Serious disease in the newborn, however, is uncommon. A pregnant woman who is not immune to chickenpox and has a prolonged exposure to a person with the disease should consult with her physician about the risk to herself and her unborn child.

Prevention

The use of varicella vaccine (Varivax(r)) is the best way to prevent chickenpox. According to CDC, the vaccine protects about 70 to 90 percent of people who receive it. CDC's Advisory Committee on Immunization Practices recommends that a single dose of the vaccine be given routinely to children ages 12 months to 12 years old who have not had chickenpox and who have not been vaccinated. It also recommends that persons older than 13 years of age who have not had chickenpox receive two injections of the vaccine, especially those in high-risk groups such as:

• Teachers of young children, day care employees and residents and staff in institutional settings.

• College students and military personnel.

• Nonpregnant women of childbearing age.

• Family and health care workers who have not had chickenpox and who are in close contact with persons who may suffer serious complications if infected with chickenpox.

• International travelers, especially if they expect to have close contact with local populations.

Consult your doctor for more information about varicella vaccine.

A question remains about how long the vaccine's protection will last. Recent studies show that protection should last at least ten years, but it is still not known if a booster will be needed later in life.

For information about shingles (herpes zoster) contact:

National Institute of Neurological Disorders and Stroke
Building 31, Room 8A-16
31 Center Drive, MSC 2540
Bethesda, MD 20892-2540

NIAID, a component of the National Institutes of Health, supports research on AIDS, tuberculosis and other infectious diseases as well as allergies and immunology.

Prepared by:
Office of Communications
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892

U.S. Department of Health and Human Services

Information provided by the NIH.