Chickenpox

Definition

Chickenpox (also called varicella) is a common, extremely infectious, rash-producing childhood disease that also affects adults on occasion.

Description

Chickenpox is caused by the varicella-zoster virus (a member of the herpes virus family), which is spread through the air or by direct contact with an infected person. It produces an itchy, blistery rash that typically lasts about a week and is sometimes accompanied by a fever or other symptoms. A single attack of chickenpox almost always brings lifelong immunity against the disease. Because the symptoms of chickenpox are easily recognized and in most cases merely unpleasant rather than dangerous, treatment can almost always be carried out at home. Severe complications can develop, however, and professional medical attention is essential in some circumstances.

Once someone has been infected with the virus, an incubation period of about 10 to 21 days passes before symptoms begin. The period during which infected people are able to spread the disease is believed to start one or two days before the rash breaks out and to continue until all the blisters have formed scabs, which usually happens four to seven days after the rash breaks out but may be longer in adolescents and adults. For this reason, doctors recommend keeping children with chickenpox away from school for about a week. It is not necessary, however, to wait until all the scabs have fallen off.

Prior to the use of the varicella vaccine, chickenpox was a typical part of growing up for most children in the industrialized world. The disease can strike at any age, but throughout the twentieth century by ages nine or ten about 80 to 90 percent of American children had already been infected. U.S. children living in rural areas and many foreign-born children were less likely to be immune. Study results reported by the Centers for Disease Control and Prevention (CDC) indicate that more than 90 percent of American adults are immune to the chickenpox virus. Adults, however, are much more likely than children to suffer dangerous complications. More than half of all chickenpox deaths occur among adults.

Demographics

Before the varicella vaccine (Varivax) was released for use in 1995, nearly all of the 4 million children born each year in the United States contracted chickenpox, resulting in hospitalization in five of every 1,000 cases and 100 deaths. Because almost every case of chickenpox, no matter how mild, leads to lifelong protection against further attacks, adults account for less than 5 percent of all cases in the United States.

Causes and symptoms

A case of chickenpox usually starts without warning or with only a mild fever and a slight feeling of unwellness. Within a few hours or days small red spots begin to appear on the scalp, neck, or upper half of the trunk. After another 12 to 24 hours the spots typically become itchy, fluid-filled bumps called vesicles, which continue to appear in crops for the next two to five days. In any area of skin, lesions of a variety of stages can be seen. These blisters can spread to cover much of the skin, and in some cases also may be found inside the mouth, nose, ears, vagina, or rectum. Some people develop only a few blisters, but in most cases the number reaches 250 to 500. The blisters soon begin to form scabs and fall off. Scarring usually does not occur unless the blisters have been scratched and become infected. Occasionally a minor and temporary darkening of the skin (called hyperpigmentation) is noticed around some of the blisters. The degree of itchiness can range from barely noticeable to extreme. Some chickenpox sufferers also have headaches, abdominal pain , or a fever. Full recovery usually takes five to ten days after the first symptoms appear. Again, the most severe cases of the disease tend to be found among older children and adults.

Although for most people chickenpox is no more than a matter of a few days' discomfort, some groups are at risk for developing complications, the most common of which are bacterial infections of the blisters, pneumonia, dehydration, encephalitis , and hepatitis. Some of the groups at greater risk are:

• Infants: Complications occur much more often among children younger than one year old than among older children. The threat is greatest to newborns, who are more at risk of death from chickenpox than any other group. Under certain circumstances, children born to mothers who contract chickenpox just prior to delivery face an increased possibility of dangerous consequences, including brain damage and death. If the infection occurs during early pregnancy, there is a small (less than 5%) risk of congenital abnormalities.
• Immunocompromised children: Children whose immune systems have been weakened by a genetic disorder, disease, or medical treatment usually experience the most severe symptoms of any group. They have the second-highest rate of death from chickenpox.
• Adults and children 15 and older: Among this group, the typical symptoms of chickenpox tend to strike with greater force, and the risk of complications is much higher than among young children.

Immediate medical help should always be sought when anyone in these high-risk groups contracts the disease.

Diagnosis

Where children are concerned, especially those with recent exposure to the disease, diagnosis can usually be made at home, by a school nurse, or by a doctor over the telephone if the child's parent or caregiver is unsure that the disease is chickenpox.

Treatment

With children, treatment usually takes place in the home and focuses on reducing discomfort and fever. Because chickenpox is a viral disease, antibiotics are ineffective against it.

Applying wet compresses or bathing the child in cool or lukewarm water once a day can help the itch. Adding four to eight ounces of baking soda or one or two cups of oatmeal to the bath is a good idea (oatmeal bath packets are sold by pharmacies). Only mild soap should be used in the bath. Patting, not rubbing, is recommended for drying the child off, to prevent irritating the blisters. Calamine lotion (and some other kinds of lotions) also reduces itchiness. Because scratching can cause blisters to become infected and lead to scarring, the child's nails should be cut short. Of course, older children need to be warned not to scratch. For babies, light mittens or socks on the hands can help guard against scratching.

If mouth blisters make eating or drinking an unpleasant experience, cold drinks and soft, bland foods can ease the child's discomfort. Painful genital blisters can be treated with an anesthetic cream recommended by a doctor or pharmacist. Antibiotics often are prescribed if blisters become infected.

Fever and discomfort can be reduced by acetaminophen or another medication that does not contain aspirin. Aspirin and any medications that contain aspirin or other salicylates must not be used with chickenpox, for they appear to increase the chances of developing Reye's syndrome . The best idea is for a parent to consult a doctor or pharmacist to confirm which medications are safe.

Immunocompromised chickenpox sufferers are sometimes given an antiviral drug called acyclovir (Zovirax). Studies have shown that Zovirax also lessens the symptoms of otherwise healthy children and adults who contract chickenpox, but the notion that it should be

used to treat the disease among the general population, especially in children, is controversial.

Prognosis

Most cases of chickenpox run their course within a week without causing lasting harm. However, there is one long-term consequence of chickenpox that strikes about 20 percent of the population, particularly people 50 and older. Like all herpes viruses, the varicella-zoster virus never leaves the body after an episode of chickenpox. It lies dormant in the nerve cells, where it may be reactivated years later by disease or age-related weakening of the immune system. The result is shingles (also called herpes zoster), a painful nerve inflammation, accompanied by a rash that usually affects the trunk or the face for ten days or more. Especially in the elderly, pain, called postherpetic neuralgia, may persist at the site of the shingles for months or years. As of 2004, two relatively newer drugs for treatment of shingles are valacyclovir (Valtrex) and famciclovir (Famvir), both of which stop the replication of herpes zoster when administered within 72 hours of appearance of the rash. The effectiveness of these two drugs in immunocompromised patients has not been established, and Famvir was not recommended for patients under 18 years.

Prevention

A substance known as varicella-zoster immune globulin (VZIG), which reduces the severity of chickenpox symptoms, is as of 2004 available to treat immunocompromised children and others at high risk of developing complications. It is administered by injection within 96 hours of known or suspected exposure to the disease and is not useful after that. VZIG is produced as a gamma globulin from blood of recently infected individuals.

A vaccine for chickenpox became available in the United States in 1995 under the name Varivax. Varivax is a live, attenuated (weakened) virus vaccine. It has been proven to be 85 percent effective for preventing all cases of chickenpox and close to 100 percent effective in preventing severe cases. Side effects are normally limited to occasional soreness or redness at the injection site. CDC guidelines state that the vaccine should be given to all children (with the exception of certain high-risk groups) at 12 to 18 months of age, preferably when they receive their measles-mumps-rubella vaccine. For older children, up to age 12, the CDC recommends vaccination when a reliable determination that the child in question has already had chickenpox cannot be made. Vaccination also is recommended for any older child or adult considered susceptible to the disease, particularly those, such as healthcare workers and women of childbearing age, who face a greater likelihood of severe illness or transmitting infection. A single dose of the vaccine was once thought sufficient for children up to age 12; older children and adults received a second dose four to eight weeks later. However, an outbreak at a daycare center in 2000 brought concern in the medical community about a second vaccination for younger children, since many of the affected children had been vaccinated. Researchers began recommending a second vaccination in 2002. In 1997, the cost of two adult doses of the vaccine in the United States was about $80. Although this cost was not always covered by health insurance plans, children up to age 18 without access to the appropriate coverage could be vaccinated free of charge through the federal Vaccines for Children program. Varivax is not given to patients who already have overt signs of the disease. It was once thought unsafe for children with chronic kidney disease, but a 2003 report said the vaccination was safe in these children. The finding is important, since even chickenpox can be a serious complication in children who must undergo a kidney transplant.

The vaccine also is not recommended for pregnant women, and women should delay pregnancy for three months following a complete vaccination. The vaccine is useful when given early after exposure to chickenpox and, if given in the midst of the incubation period, it can be preventative. The Infectious Diseases Society of America stated in 2000 that immunization is recommended for all adults who have never had chickenpox.

While there was initial concern regarding the vaccine's safety and effectiveness when first released, the vaccination is in the early 2000s gaining acceptance as numerous states require it for admittance into daycare or public school. In 2000, 59 percent of toddlers in the United States were immunized; up from 43.2 percent in 1998. A study published in 2001 indicates that the varicella vaccine is highly effective when used in clinical practice. Although evidence has not ruled out a booster shot later in life, all research addressing the vaccine's effectiveness throughout its six-year use indicates that chickenpox may be the first human herpes virus to be wiped out. Although initial concerns questioned if the vaccination might make shingles more likely, studies are beginning in the early 2000s to show the effectiveness of the vaccine in reducing cases of that disease.

Parental concerns

A doctor should be called immediately if any of the following occur:

• The child's fever goes above 102°F (38.9°C) or takes more than four days to disappear.
• The child's blisters appear infected. Signs of infection include leakage of pus from the blisters or excessive redness, warmth, tenderness, or swelling around the blisters.
• The child seems nervous, confused, unresponsive, or unusually sleepy; complains of a stiff neck or severe headache ; shows signs of poor balance or has trouble walking; finds bright lights hard to look at; is having breathing problems or is coughing a lot; is complaining of chest pain; is vomiting repeatedly; or is having convulsions. These may be signs of Reye's syndrome or encephalitis, two rare but potentially dangerous conditions.

Resources

BOOKS

Arvin, Ann M. "Varicella-zoster Virus." In Principles and Practice of Pediatric Infectious Diseases , 2nd ed. Edited by Sarah S. Long et al. St. Louis, MO: Elsevier, 2003.

Myers, Martin G., et al. "Varicella-Zoster Virus." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.

PERIODICALS

Arvin, Ann M. "Varicella Vaccine: The First Six Years." New England Journal of Medicine (March 2001).

"Chickenpox Vaccine OK for Pediatric Patients." Vaccine Weekly (January 22, 2003): 25.

Henderson, C. W. "Chickenpox Immunization Confirmed Effective in Adults." Vaccine Weekly (September 2000): 22.

"Study: Two Vaccines Work Best." Vaccine Weekly (January 8, 2003): 14.

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: http://www.cdc.gov.

WEB SITES

"Chickenpox." MedlinePlus. Available online at http://www.nlm.nih.gov/medlineplus/chickenpox.html (accessed December 25, 2004).

Beth A. Kapes Teresa G. Odle Rosalyn Carson-DeWitt, MD