Chickenpox

Chickenpox is a highly contagious viral infection characterized by an itchy, blister-like rash. The infection is typically mild in healthy children. Chickenpox can cause more severe symptoms or complications in adolescents and adults and in people of all ages who have weak immune systems. If contracted during pregnancy, chickenpox can cause severe symptoms and pose significant risks to the developing baby.


Causes/associated factors
Chickenpox is caused by the varicella zoster virus. About 85 percent of all chickenpox cases develop in children age 14 and younger. Although there have been rare cases of reinfection (particularly among people who have weak immune systems), once you've had chickenpox you're considered immune for the rest of your life.
Chickenpox occurs most often during the winter and spring. In the United States, the greatest number of cases occur from March to May. Before the chickenpox vaccine was widely available, chickenpox led to at least 11,000 hospitalizations and 100 deaths each year in the United States.


Transmission
The incubation period (time from exposure until symptoms appear) may last from 10 to 21 days. The average is 15 days. Chickenpox is contagious starting about 48 hours before the rash appears through about six days after, or as long as the sores aren't crusted over.
For chickenpox to develop, the virus must enter your respiratory tract. Usually this occurs through contact with infected droplets coughed or sneezed into the air or passed from someone's hand. It can also occur after direct contact with the rash of a person infected with chickenpox or shingles, an infection caused by the same virus that causes chickenpox. (After you've had chickenpox, the virus can lodge inside certain nerve cells and remain inactive for years. If it reactivates, it causes a rash known as shingles.)

Because chickenpox spreads so easily, it often affects all the children in a single family. It also spreads rapidly through child care facilities and classrooms, partly because the contagious period begins before the rash is visible. Because chickenpox is so contagious, many doctors only see those patients whom they feel need a physical exam. Even then, patients who have chickenpox are usually ushered into the office through a separate door.


Signs/symptoms
Before developing a visible rash, you may experience a 24- to 48-hour period of generalized fatigue. You may also have a low-grade fever. Although this phase of the illness may go unnoticed, it's often the time when you're most likely to infect others.
After the initial 24 to 48 hours, you'll develop an itchy rash that looks like flat, red splotches. The rash may develop anywhere on your body, but usually begins on the scalp and moves to the trunk and then the arms and legs. It's often most noticeable on the trunk.

During the next stage, the flat, red blotches develop into raised spots that look like small pimples. Eventually, these pimples fill with clear fluid and turn into blisters that resemble drops of water on red bases. Your fever may be highest during this time.

Finally, the blisters break and form crusts. You may have intense itching when this happens, and the fever usually disappears. The crusts typically fall off between nine and 13 days after the rash appears. The entire cycle may repeat itself two to four times over the next two to six days. Symptoms are usually more severe in healthy adolescents and adults than healthy children. Symptoms may also be more severe in people who have weak immune systems.


Diagnosis
The doctor will ask questions about your medical history, do a physical exam and observe the distinctive rash. At the same time, the doctor may identify or rule out other conditions that may cause a rash, such as a drug interaction, impetigo (a contagious, superficial skin infection that mainly affects children) or dermatitis (inflammation of the upper layers of skin).
For otherwise healthy children, routine chickenpox can typically be diagnosed through a physical exam and careful observation of the rash. Lab tests aren't usually needed to confirm the diagnosis.

In complicated cases, special tests may be needed to confirm the viral origin of the illness or evaluate immune responses. A significant increase in white blood cell count may suggest a secondary bacterial infection.


Treatment
For some adults, adolescents or people at increased risk for moderate to severe infection (such as those with a chronic skin or lung disorder or those taking aspirin or corticosteroid therapy), an antiviral medication such as acyclovir may be prescribed to keep the chickenpox virus from reproducing within the body. The antiviral medication must be taken within 24 hours after the rash appears.
An antiviral medication isn't typically recommended for routine chickenpox in otherwise healthy children because the therapeutic effect is marginal and the treatment is costly. In these cases, the infection is typically allowed to run its course.

Itching may be intense, but it's important to avoid scratching to prevent infecting the chickenpox sores. These tips may help:

Keep your fingernails short and clean, and wash your hands often with an antibacterial soap.

Wear lightweight gloves.

Stay in a cool, comfortable environment.

Relieve itching with cool wet compresses, a cool bath, an oatmeal or baking soda bath, or calamine lotion.

Take an antihistamine medication, such as diphenhydramine, if recommended by your doctor.
During the illness, don't give aspirin or products containing aspirin to children age 19 or younger. Aspirin is linked to Reye's syndrome, a rare but serious illness. The doctor may recommend acetaminophen instead.


Complications
Complications are most common in adolescents, adults and people who have weak immune systems. Serious complications of chickenpox include:
secondary bacterial infections of the chickenpox sores with possible scarring
dehydration
pneumonia
encephalitis (inflammation of the brain)
myocarditis (inflammation of the heart muscle)
hepatitis (inflammation of the liver)
nephritis (inflammation of the kidney)
blood clotting problems
Having chickenpox has become one of the most important risk factors for developing a serious group A streptococcal infection. The group A streptococcal bacterium usually causes relatively minor illness, but when it invades tissues such as the blood, muscle or lungs, a life-threatening infection can result. The bacterium has become known as the "flesh-eating bacteria." Although rare, these infections have been noted with increasing frequency following chickenpox.

Reye's syndrome is a rare complication today thanks to the widespread avoidance of aspirin among anyone age 19 or younger who has chickenpox.


Pregnancy-specific information
If you haven't had chickenpox or are unsure of your immunity, avoid exposure to anyone who has chickenpox or shingles while you're pregnant.
If you suspect you have chickenpox or have never had it but are exposed to someone who does, contact your doctor immediately. The infection can cause severe symptoms and pose significant risks to you and the baby. There's currently no effective treatment to prevent spreading the infection to the baby.


Senior-specific information
Chickenpox can be a potentially severe infection for the few older adults who aren't immune to the illness. If you're not immune to chickenpox, ask your doctor if the chickenpox vaccine is appropriate for you.
Shingles
Again, shingles, also known as herpes zoster, is an illness caused by the same virus that causes chickenpox. This illness is most common in adults age 50 and older.

You can only develop shingles if you've already had chickenpox. Here's how it works: After the chickenpox infection, the virus can lodge inside the nerve cells near your spinal cord and cranial nerves (a part of the central nervous system called the dorsal root ganglion). The virus may be inactive for years. If it "reactivates," you have shingles. The virus moves along the nerve pathways of your skin, eyes and ears, causing severe pain and a blistering rash.

As a rule, shingles is more common in older people, those who have weak immune systems, and children who were born with congenital varicella syndrome or developed chickenpox before age 1. Of course, rare exceptions may exist.

Here are some other factors to consider:

A person who has an active case of shingles can infect another person with chickenpox if the other person has never had chickenpox or has never been immunized.
A person who has an active case of shingles cannot cause someone who has either had chickenpox previously or has been immunized to develop chickenpox again, except in rare instances when a second chickenpox infection occurs.
Prevention
Do everything possible to keep infected people isolated until the sores have crusted over. Chickenpox can be risky to adults, those who have weak immune systems, infants and pregnant women.
Believing that it's better for a child to develop this illness at a young age or before starting school, some parents wonder if they should deliberately expose their child to the illness. This isn't recommended, however, because serious complications -- though rare -- can result from chickenpox. It's much better to prevent chickenpox by making sure your child is immunized.

Chickenpox vaccine
The U.S. Food and Drug Administration (FDA) approved Varivax, the first chickenpox vaccine, in 1995. The vaccine is a live vaccine made of a weakened form of the chickenpox virus. Immunity usually develops within four to six weeks of vaccination.

The vaccine offers about 85 percent protection from infection and decreases the severity of the infection should you become infected. The length of protection is uncertain, but appears to be long-lasting. A new study found that the vaccine was 97 percent effective for the first year after vaccination, but the effectiveness decreased to 84 percent in the second to eighth year. A booster isn't currently recommended.

Widespread use of the chickenpox vaccine is expected to decrease the number of chickenpox cases and complications for both children and adults. In fact, the Advisory Committee on Immunization Practices (ACIP) recently strengthened its recommendations for vaccination. The group now recommends that each state require proof of immunity for entry into child care and school, either through immunization or a bout with the disease itself.

For healthy children and adults, here are the recommended guidelines for chickenpox vaccination:

Children between ages 12 and 18 months who haven't had chickenpox should receive one dose. This dose can be given at the same time as the first measles vaccination.

Children between ages 18 months and 12 years who haven't had chickenpox should receive one dose as soon as possible.

Healthy people age 13 and older who haven't had chickenpox should have two doses, four to eight weeks apart. This includes women of childbearing age who aren't pregnant and all healthy adolescents and adults, especially those at high risk of exposure to or transmission of chickenpox, such as:
health care workers
household or other close contacts of people who have weak immune systems
those living in households with children
child care workers and teachers of young children
residents and staff in institutional settings
college students
military personnel
international travelers
Prevention after exposure
If you've been exposed to chickenpox and haven't had the illness or been immunized, receiving the vaccine within three days (and possibly up to five) of exposure may prevent chickenpox from developing or decrease its severity.

If you've been exposed to chickenpox and have a high risk of developing complications from an infection, you may be given varicella zoster immune globulin (VZIG, a protein that can act as an antibody, a compound that helps neutralize or destroy foreign substances in the blood). The sooner VZIG is given after possible exposure to the virus, the more likely it is to prevent infection. To be effective, VZIG must be taken within 96 hours of exposure. How long the protection lasts is not known.

If you haven't had chickenpox but have been exposed to the illness, isolate yourself during the 10- to 21-day incubation period, especially if you're in contact with people at high risk for complications from chickenpox.