Infection: Chickenpox

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

Chickenpox or varicella is a highly infectious disease caused by a virus. It is usually a mild disease that used to be common in schoolchildren before 1995, when a vaccine against it was introduced in the United States. It does occasionally produce complications, however, particularly in adults who become infected with it and those with a weakened immune system.

Description

Chickenpox is a highly contagious disease that spreads rapidly because people can transmit the virus for several days before they feel sick. In most people, the virus enters the body through the nose and throat when the person breathes in air that contains the virus or droplets from an infected person's sneezing or coughing. Once inside the body, the virus multiplies in the lymph nodes of the upper respiratory tract for two to four days after the infection begins. It then enters the bloodstream and travels to the spleen and liver, where it continues to multiply for another week or ten days. At this point the virus invades the skin and begins to produce the skin rash that is a classic sign of chickenpox.

The rash begins as red macules, or flat spots, on the surface of the face and body. Most children have about 250–500 of these spots but may have as many as 1,500. The spots develop in a series of crops or batches that go through characteristic stages. The flat macules grow over a period of ten to twelve hours into papules, or raised reddish pimples. The papules in turn become vesicles, which are fluid-filled blisters that at first look like a dewdrop on a rose petal. The vesicles eventually burst

and turn into open sores before crusting over. One of the distinctive marks of chickenpox is that the child will have rashes in several different stages at the same time. The child is contagious until the last of the vesicles has burst and has completely crusted over.

The most common complication of chick-enpox is a secondary bacterial infection, which can happen if the child scratches the vesicles and bacteria invade the raw skin underneath. An infection can produce inflammation of the skin and a high fever. Impetigo, another skin disease characterized by sores covered with honey-colored crusts and eventual scarring of the skin, can also result. In some cases bacteria can invade the bloodstream, leading to eventual bacterial pneumonia or infection of the middle ear. Because of the risk of bacterial infection, it is important to keep a child with chickenpox from scratching the skin rash.

Another possible complication is the transmission of the chickenpox virus from a mother who develops the disease to the unborn baby. A baby whose mother develops chickenpox within five days before delivery or two days after delivery can become very sick from the virus if the mother is not treated.

Demographics

Before 1995, chickenpox was considered one of the classic diseases of childhood, along with measles and mumps; about 4 million cases were reported each year in the United States. About 11,000 people were hospitalized annually with chickenpox in North America, and between fifty and 100 of these people died. Since 1995, the number of cases in the United States has declined about 90 percent, and there are only about ten deaths from chickenpox reported each year—most of them in people who were not immunized. In the United States and Canada, about 90 percent of cases of chickenpox occur in children younger than fourteen years, with the remaining 10 percent affecting older teenagers and adults.

There are about 90 million cases of chick-enpox reported around the world each year. Whereas chickenpox is most common in children between the ages of one and fourteen years in countries with temperate climates, it affects as many adults as children in countries with tropical climates. In North America chickenpox is most common in late winter and spring.

As far as is known, chickenpox strikes all races and both sexes equally.

Causes and Symptoms

Chickenpox is caused by a virus known as the varicella-zoster virus or VZV. This virus is a member of a family of viruses called human herpesviruses; it is related to the viruses that cause oral and genital herpes infections. The chickenpox virus can be spread by breathing air containing droplets from an infected person's sneezing or coughing, or by direct contact with an infected person or their clothing.

The earliest symptoms of chickenpox occur during its prodrome, a brief period of time that precedes the main symptoms of a disease. During the prodrome, which is more likely to occur in teenagers and adults than in younger children, the person may complain of a headache, nausea, general tiredness, and loss of appetite. In many children, the first sign of chickenpox is the appearance of the characteristic rash, accompanied by tiredness and a low-grade fever of 100–102°F (37.8–38.9°C). In a few children the fever may rise as high as 106°F (41.1°C).

Did You Know?

Chickenpox did not get its name because it infects chickens or because humans can get it from eating chickens. The disease was first described in Europe by an Italian doctor named Giovanni Filippo (1510 – 1580), who gave it its alternate name of varicella. The English word “chickenpox” may come from the fact that the blisters of the skin rash associated with the disease looked like chickpeas to a doctor named Richard Morton, who first wrote about chickenpox in English in the seventeenth century. Chickpeas are sometimes called garbanzo beans; they are edible peas that are often eaten in salads or cooked in stews.

The characteristic rash of chickenpox has already been described. It takes about a week for each crop of macules to move through the complete cycle of forming papules, vesicles, and crusted sores. Successive crops of macules usually appear for five to seven days, which means that the child should be considered contagious for at least a week after the appearance of the last group of macules. Fever rarely lasts longer than four days. The child may not feel like eating if there are vesicles forming inside the mouth or throat; the sick child should, however, be encouraged to drink plenty of fluids to prevent dehydration.

Diagnosis

The doctor usually diagnoses chickenpox on the basis of its external signs and symptoms; in most cases it is not necessary to take a sample of blood or fluid from the vesicles for a laboratory test. In many cases the doctor is helped in diagnosing the disease by asking whether the child has been exposed to anyone with chickenpox in the last ten to twenty-one days.

It is possible to identify the chickenpox virus in samples of fluid taken from the patient's vesicles, but these tests are expensive, some are slow and may not be reliable, and others require special laboratory equipment that is not readily available to most doctors.

Treatment

Chickenpox is considered a self-limiting disease; that is, people usually recover from it without requiring special treatments. Children with chickenpox should be kept home from school or daycare to avoid infecting others; however, they do not need bed rest. They should stay home until all the chickenpox blisters have completely crusted over.

The child's fingernails should be trimmed short to prevent the blisters from becoming infected if the child scratches them. Very young children may need to have their hands covered with mittens to reduce the risk of infection from scratching. For relief from the itching caused by the skin rash, children can be bathed in cool water with baking soda added every three to five hours. Other treatments for the itching include Aveeno oatmeal baths, application of calamine lotion, or oral antihistamines.

Children can be given acetaminophen or ibuprofen to bring down the fever and to relieve the headache and sore muscles that sometimes accompany chickenpox. They should never be given aspirin, however, because of the risk of Reye syndrome. Reye syndrome is a two-stage illness of young children that follows a viral infection with fever like chick-enpox or flu and is thought to be linked to taking aspirin for the fever.

People with weakened immune systems, such as those with HIV infection or leukemia, should be treated with acyclovir (Zovirax), which is a drug that is usually given to treat oral or genital herpes. Acyclovir can reduce the time it takes for a person with a weak immune system to recover from chickenpox. In addition, adults who develop chickenpox should be given acyclovir because they are at greater risk than children of developing complications, such as pneumonia.

Prognosis

Most children with chickenpox recover completely; however, some develop skin infections as a result of scratching the blisters, and about 5 percent may develop earaches or pneumonia if the bacteria infecting the skin sores have gotten into the bloodstream. Another common complication is shingles, an inflammation of the skin caused by a flare-up of the chickenpox virus that has remained in the nervous system after the child has recovered from chickenpox itself. Shingles, or herpes zoster, usually occurs decades after the chickenpox episode.

Children with leukemia have a 7 percent mortality rate from chick-enpox. In otherwise healthy children, the mortality rate is about two per 100,000 cases.

Prevention

Most people who recover from chickenpox are immune for their the rest of their lives; it is very unusual for a person who has had chickenpox in childhood to have it again as an adult. Chickenpox can be prevented by immunization with the vaccine introduced in 1995. The vaccine, called Varivax, is known to be effective for at least eight years; however, its longer-term effectiveness needs further study. As of 2008 the American Academy of Pediatrics (AAP) recommended two immunizations with Varivax, the first dose given to infants between twelve and fifteen months of age and the second given to children between the ages of four and six years. Some states have made vaccination for chickenpox mandatory alongside vaccinations for polio, mumps, and measles.

It is important for a woman who is pregnant and has never had chickenpox to check with her doctor about her immune status. Pregnant women or babies younger than one year are not given Varivax. They and people with weak immune systems can be protected against chickenpox by receiving varicella-zoster immune globulin, or VZIG, a preparation made from human immunoglobulin. A pregnant woman who develops chickenpox within five days before her due date or two days after childbirth should be given VZIG and acyclovir to protect the baby's health.

The Future

Chickenpox is likely to become a less common disease in developed countries if the use of Varivax becomes widespread. The disease is not likely to become extinct, however, because people in developing countries often cannot afford the vaccine.

Although there has been a tendency on the part of some parents in recent years to avoid having children vaccinated for childhood diseases in the belief that the vaccines have too many side effects, doctors now warn against this attitude.

SEE ALSO Genital herpes; Reye syndrome

WORDS TO KNOW

Macule: A spot on the skin or patch that is different in color from normal skin but is usually not raised up above the skin surface.

Papule: A small cone-shaped pimple or elevation of the skin.

Prodrome: A group of warning signs or symptoms that appear before the onset of a disease.

Shingles: A skin inflammation caused by reactivation of the chickenpox virus remaining in the nervous system.

Vesicle: A small blister or sac containing fluid.

For more information

BOOKS

Glaser, Jason. Chicken Pox. Mankato, MN: Capstone Press, 2006.

Powell, Jillian. Chicken Pox. North Mankato, MN: Cherrytree Publishing, 2007.

PERIODICALS

Abruzzese, Sarah. “Maryland Parents Told to Have Children Immunized.” New York Times, November 18, 2007. Available online at http://www.nytimes.com/2007/11/18/us/18vaccine.html (accessed April 2, 2008).

Sachs, Jessica Snyder. “Nice Shot.” New York Times, October 10, 2007. Available online at http://www.nytimes.com/2007/10/10/opinion/10sachs.html (accessed April 2, 2008).

WEB SITES

Centers for Disease Control and Prevention (CDC). Vaccines and Preventable Diseases: Varicella Disease Questions and Answers. http://www.cdc.gov/vaccines/vpd-vac/varicella/dis-faqs-gen.htm.

JAMA Patient Page. Chickenpox. Available in PDF format at http://jama.ama-assn.org/cgi/reprint/294/7/866.pdf (first posted August 17, 2005; accessed April 2, 2008).

KidsHealth. Chickenpox. http://www.kidshealth.org/parent/infections/common/chicken_pox.html.