Chickenpox

Overview

Chickenpox, also known as varicella, is a highly contagious and self-limited infection that most commonly affects children between 5-10 years of age. The disease has a worldwide distribution and is reported throughout the year in regions of temperate climate. The peak incident is generally during the months of March through May. Lifelong immunity for chickenpox generally follows the disease. If the patient's immune system does not totally clear the body of the virus, it may retreat to skin sensory nerve cell bodies where it is protected from the patient's immune system. The disease shingles (also known as "zoster") represents release of these viruses down the length of the skin nerve fiber and produces a characteristic painful rash. Shingles is most commonly a disease of adults.

Chickenpox Causes

The Varicella-zoster virus (VZV) causes chickenpox. The disease is highly contagious -- over 90% of nonimmune individuals will develop chickenpox following exposure. VZV is communicable by both direct skin-to-skin contact and via respiratory droplets (for example, coughing, sneezing) from the infected individual. While the average incubation period from viral exposure to onset of symptoms is 12-14 days, a broader post-exposure window of 10-21 days is quoted in the literature.

Chickenpox Symptoms

Rash

Healthy children generally experience one to two days of fever, sore throat, and malaise approximately two weeks following exposure to VZV. Within 24 hours of these symptoms, a characteristic rash develops initially on the torso and then spreads over the next seven to 10 days outward to the head, arms, and legs. The rash progresses through a predictable evolution from a red papule ("bug bite") appearance to blister ("vesicle") to pustule and then scabs over. The vesicle and pustular fluids are highly concentrated with infectious virus particles. New lesions characteristically come in "waves" over the skin surface. The patient may thus have newly formed papules, middle-aged vesicles and pustules, and crusted lesions all at the same time. At the peak of the disease, a patient may have over 300 skin lesions at one time. Once all lesions are scabbed over, the person is no longer contagious. The lesions rarely cause permanent scarring, unless secondary infection develops (see below). Lesions may commonly be found in the mouth and may also involve the genitalia.

Complications

In healthy children, chickenpox is a mild disease. Adults are 25% more likely to have significant complications. Common complications affecting both children and adults include

Skin infection: Secondary bacterial infections caused by either Staphylococcus or Streptococcus bacteria are well described. Rarely, an invasive form of Streptococcus can quickly spread throughout the body and may be life-threatening;


Pneumonia: This is a relatively rare complication in healthy children, but is the primary cause of hospitalization for adults (one in 400 cases) and has a mortality (death) rate of between 10%-30%;


Neurologic complications: Children most commonly develop an inflammation of the balance center of the brain called acute cerebellar ataxia. Symptoms of abnormal eye movements and poor balance develop in about one in 4,000 children approximately one week into the skin manifestations of chickenpox. Symptoms generally last for a few days, and a complete recovery is common. Adults more commonly develop a more generalized brain inflammation ("encephalitis") whose symptoms may include delirium and seizures. Some studies report a 10% mortality rate and a 15% rate of developing long-term neurologic side effects in survivors;


Reye syndrome: This rare childhood complication of chickenpox (and influenza) is most commonly associated with the administration of aspirin. A rapid progression of nausea, vomiting, headache, delirium, and combativeness that may progress to coma is a common pattern of deterioration. Supportive measures are the only therapy; and


Rare complications: Hepatitis, kidney disease, ulcers of the intestinal tract, and inflammation of the testes (orchitis) have all been described.

Chickenpox and pregnancy

The first case of pregnancy-associated complications of VZV was reported in 1947. Further studies have shown that most cases of congenital (in the womb) infection occur in infants whose mothers were infected with VZV between eight and 20 weeks' gestation. Congenital infection occurs only in infants born to mothers who experience VZV clinical infection (chickenpox) during pregnancy. Women who are immune to VZV and are exposed to chickenpox during pregnancy do not carry the same risk profile for their infant. Studies indicate that the risk of fetal anomalies as a result of congenital VZV infection is very small (0.4%-2%). Complications that have been documented include: skin pigment abnormalities and scarring (presumably due to intrauterine skin infections), eye abnormalities, brain structural abnormalities resulting in mental retardation, and structural abnormalities of the arms and legs. Maternal shingles during any trimester of pregnancy has not been associated with congenital abnormalities. Non-VZV-immune pregnant women can be reassured that localized shingles (zoster) infection is only contagious from direct contact with open lesions.

Maternal VZV infection during the final two weeks of a pregnancy carries an ominous risk for the infant. Infected infants have up to a 25% mortality rate, and the worse prognosis exists for those infants whose mothers developed chickenpox during the last five days of confinement. Overwhelming generalized sepsis (infection of the bloodstream that spreads throughout the body) and multiple organ infection and failure lead to such a dismal prognosis. Specific anti-VZV gamma globulin can be used to lessen the severity of neonatal disease

When to Seek Medical Care

Although most cases of chickenpox heal without complications, sometimes medical attention is required. Call the doctor if any of the following conditions develop:
Fever higher than 103°F


A rash involving an eye; eye pain (especially unusual sensitivity to light)


Dehydration, vomiting, or decreased fluid intake


Uncertainty of diagnosis or what medication to give


Secondary skin infections


Signs of bacterial infection include the following:


Blisters leaking a thick yellow or green fluid


Areas around a blister are red, increasingly painful, or swollen, or have red streaking extending from the site

If someone with chickenpox begins to breathe with difficulty, shows confusion, disorientation, or appears extremely sleepy and becomes belligerent or difficult to wake up, go immediately to a hospital's emergency department. In addition, any seizures or high fever accompanied by headache and vomiting need prompt emergency evaluation

Exams and Tests

A doctor usually bases a diagnosis of chickenpox on the clinical history and physical findings. However, laboratory exams can be useful. Your doctor can test blister fluid if there is a concern about secondary skin infection by Staphylococcus or Streptococcus. If the blisters are infected with bacteria, such a bacterial culture can help determine which antibiotics may be needed.

Chickenpox Treatment


Self-Care at Home

Most cases of chickenpox can be managed at home. Chickenpox rash tends to be extremely itchy. Several treatments can be used at home to help a child feel better.
Cool compresses applied to blisters may give relief, as may calamine lotion. Lotions containing diphenhydramin (Benadryl) should not be used -- erratic absorption through open skin lesions may occur and be associated with toxicity due elevated blood levels.
You can give cool-water baths every three to four hours, adding baking soda to the water to calm itching. You may also soak in an Aveeno oatmeal bath to soothe itching blisters.
Trimming fingernails can help prevent infection from scratching the blisters. If you have a small infant with chickenpox, cover the child's hands with mittens to minimize scratching.
Diphenhydramine (Benadryl), loratadine (Claritin), or citirizine (Zyrtec) taken orally also can relieve itching. These medicines are available over the counter.
Treat fever with acetaminophen (for example, Tylenol) or ibuprofen (for example, Advil, Motrin, Excedrin, Nuprin, and Pamprin are common brand names). Read the label before giving any medication. Some medicines contain many different agents. If the medicine is for a child, make sure it contains no aspirin. Never give aspirin to a child because aspirin has been associated with Reye syndrome.
Occasionally a child will develop blisters in the mouth, making eating or drinking painful. A person should be encouraged to drink fluids to prevent dehydration. To alleviate pain, provide cold fluids (ice pops, milk shakes, and smoothies) and soft bland foods. Avoid any foods that are spicy, hot, or acidic (for instance, orange juice).
Keep children at home from school and daycare until all blisters have crusted. A child with chickenpox is extremely contagious until the last crop of blisters has crusted.
If you take your child to a doctor's office, call ahead to let the staff know that you think your child has chickenpox. They may usher you to a special waiting or treatment room to avoid exposing other children.

Medical Treatment

If you have a fever, your doctor may recommend acetaminophen or ibuprofen.
If you appear dehydrated and are unable to drink fluids, your doctor may recommend IV fluids either in an emergency room or as a hospitalized patient.

Secondary bacterial skin infections may be treated with antibiotics. Because a virus causes chickenpox, no antibiotic can cure the disease.

For people who have severe infections, an antiviral agent called acyclovir (Zovirax) has been shown to shorten the duration and severity of symptoms if given soon after the onset of the rash. Acyclovir may be given by mouth or by IV to help people at risk for severe infection.
Neonatal VZV infection may be treated with VZIG (varicella zoster immune globulin) -- a form of highly concentrated anti-VZV gamma globulin. The availability of VZIG is rapidly declining since the only product manufacturer has ceased production. An alternative product, VariZIG, is available on a research protocol.

Prevention

Varivax, a two-dose vaccine for chickenpox, is highly recommended for healthy children, adolescents, and adults. Set up an immunization schedule for your child with your doctor.

When fully immunized, the vaccine has been shown to be 95% effective in preventing childhood cases of chickenpox. A small percentage of newly immunized people will develop a mild rash. Pregnant women and infants younger than 1 year of age should not be vaccinated.

Outlook

Prior to the introduction of a chickenpox vaccine program, approximately 4 million cases occurred annually in the United States; 10,000 patients were hospitalized annually, and an average of 100 deaths occurred. The majority of deaths occurred in those who had no identifiable risk factor (for example, cancer, HIV/AIDS). Chickenpox should not be viewed as a childhood "rite of passage" and is not merely an inconvenience.