Chickenpox

Chickenpox

Fig.3.15.

Definition

Chickenpox is a common and highly contagious childhood disease that also occasionally affects adults. It is caused by the varicella-zoster virus. Chickenpox produces an itchy, blistery rash that typically lasts about a week and is sometimes accompanied by fever or other symptoms.

(Fig 3.15.)
A five-year-old girl with chickenpox. The first symptom of the disease is the rash that is evident on the girl's back and neck. The rash and the mild fever that accompanies it should disappear in a week or two.



Demographics

Chickenpox is a common infectious disease with an estimated 60 million cases occurring annually worldwide. In temperate regions, the disease usually affects children under age 10; in tropical regions, adult cases are more common. The rate of infection is independent of race or gender, but is much lower in countries where vaccination against the disease is practiced. For example, before a vaccine against chickenpox was introduced in the United States in 1995, about 99% of the population got chickenpox by age 30. A decade after the vaccine was introduced, only about 10% ofAmericans who had not already had chickenpox got the disease.



Description

Chickenpox is very contagious. The virus is transmitted through either direct contact or coughing and sneezing. A person with chickenpox is contagious from one to two days before the outbreak of the chickenpox rash to about six days after the rash erupts. After being exposed, a person will show symptoms of chickenpox within 10-21 days. Individuals normally get chickenpox only once in a lifetime.

Most cases of chickenpox contracted by healthy children are mild, with the child experiencing seven to 10 days of discomfort. However, in children who are immunocompromised, such as those with leukemia, AIDS, or who are undergoing immunosuppression therapy in connection with an organ transplant, chickenpox can have serious complications including death. For example, the number of children with leukemia who die of complications from chickenpox is estimated at 7% to 28%. This compares to a death rate of about seven in every 100,000 healthy children. Abnormalities may occur in the fetuses of women who develop chickenpox during the first 22 weeks of pregnancy.

Risk factors

The greatest risk factor for acquiring chickenpox is the failure to vaccinate; almost every unvaccinated person exposed to the virus develops chickenpox. It may not be safe to vaccinate some children with compromised immune systems, leaving them highly vulnerable to both the disease and severe complications including death. Pregnant women who develop chickenpox during the first half of their pregnancy put the fetus at risk for birth defects.

Causes and symptoms

Chickenpox is caused by the varicella-zoster virus, a member of the herpes virus family. It easily spreads through the air or by direct contact with an infected person.

A case of chickenpox usually starts without warning or with only a mild fever and a slight feeling of illness. Within a few hours or days, small red spots begin to appear on the scalp, neck, or upper half of the trunk. After a further 12-24 hours, the spots typically become itchy, fluid-filled bumps called vesicles, which continue to appear for the next two to five days. In any area of skin, lesions in a variety of stages can be seen. These blisters can spread to cover much of the skin, and in some cases 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 250-500.

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) develops around some of the blisters. The degree of itchiness can range from barely noticeable to extreme. Some people who contract chickenpox also have headaches, abdominal pain, or a fever. Full recovery usually takes five to 10 days after the first symptoms appear. The most severe cases of the disease tend to be found among adolescents and adults.

Although for most people chickenpox is no more than a matter of a few days of 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:

  • Infants. Complications occur much more often among children less 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 before delivery develop the disease and face an increased possibility of dangerous complications, including brain damage and death. If the infection occurs during the first half of pregnancy, there is a small risk of the baby being born with 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 age 15 and older. Among this group, typical symptoms of chickenpox tend to be more severe, and the risk of complications is much higher than among young children. Adults are ten times more likely than children to require hospitalization from chickenpox.

Diagnosis

For otherwise healthy children, especially those with recent exposure to the disease, diagnosis usually can be made at home, by a school nurse, or by a doctor if the child's parent or caregiver is unsure that the disease is chickenpox. A doctor should be called immediately if:

  • The child has a chronic disease or is undergoing a treatment that weakens the immune system.
  • 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 pus drainage or excessive redness, warmth, tenderness, or swelling.
  • 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 very dangerous conditions.

Home remedies

Treatment usually takes place at home and focuses on reducing discomfort and fever. The individual should drink plenty of fluids and eat simple, nutritious foods. Soups, herbal teas, and fruit juices are good choices. If mouth blisters make eating or drinking an unpleasant experience, cold drinks and soft, bland foods can ease the discomfort.

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

Drugs

Fever and discomfort can be reduced by acetaminophen (Tylenol, Tempera). Aspirin and any medications that contain aspirin or other salicylates must not be used for children with chickenpox because they appear to increase the chances of developing Reye's syndrome. The best idea is to consult a doctor or pharmacist if unsure about which medications are safe. Because chickenpox is a viral disease, antibiotics are ineffective against it, although antibiotics may be prescribed if blisters become infected.

Children who are immunocompromised or healthy children who develop serious complications are often treated with the antiviral drug acyclovir (Zovirax), which is given intravenously. This drug may also be used under certain circumstances in adolescents and adults with chickenpox.

A substance called varicella-zoster immune globulin (VZIG), which reduces the severity of chickenpox symptoms, may be used to treat immunocompromised children and others at high risk of developing complications. VZIG is produced from a gamma globulin from blood of recently infected individuals. It provides some degree of passive immunity when administered by injection within 96 hours of known or suspected exposure to the disease. It is not useful if givenmore than 96 hours after exposure.

Prognosis

Most cases of chickenpox run their course within a week. Although complications from chickenpox generally are rare, the most common one is bacterial infection of the skin, initiated at the site of a chickenpox blister that has broken or was scratched open. Other complications include viral or bacterial pneumonia and rarely encephalitis (swelling of the brain). Anyone with a weakened immune system, lung diseases, eczema or other skin conditions, infants under one year of age, premature infants whose mothers have not had chickenpox, and newborns whose mothers had chickenpox around the time of delivery are at highest risk for developing complications are.

After symptoms subside, the varicella-zoster virus lies dormant in nerve cells where it may be reactivated years later by disease or age-related weakening of the immune system. The result is shingles (herpes zoster), a very painful rash and nerve inflammation, that develops in between 10% and 20% of all people who have ever had chickenpox. Shingles is particularly common in people over age 50. Shingles cause numbness, itching, or severe pain in skin areas where the affected nerve root is located. Within about three days cause clusters of blisters to form along the affected nerve. The blisters last two to three weeks. A vaccine against shingles is recommended for individuals age 60 and older.

Prevention

Vaccination against the varicella-zoster virus is the best way of preventing chickenpox. Vaccination has been proven to be about 85% effective for preventing all cases of chickenpox and about 95% effective in preventing severe cases. Side effects of the vaccine normally are limited to occasional soreness or redness at the injection site. The United States Centers for Disease Control and Prevention (CDC) guidelines state that the vaccine should be given to all children (with the exception of certain high-risk groups) at 12-18 months of age, preferably when they receive their measles-mumps-rubella (MMR) 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 health care workers and women of childbearing age.

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 the permanence of immunity and the necessity of a second vaccination for younger children, since many of the affected children had already received a single dose of the vaccine. Since 2006, a second dose of the vaccine has become standard.

The chickenpox vaccine 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 may be preventative.

While there was initial concern regarding the vaccine's safety and effectiveness when first released, the vaccination has gained acceptance, and many states require it for admittance into daycare or public school. In 2004, 87.5% of toddlers ages 19-35 months in the United States were immunized; up nearly 20% from 2000.