Chickenpox (Varicella)

Topic Overview

What is chickenpox?

Chickenpox is a common illness that causes an itchy rash and red spots or blisters (pox) all over the body. It is most common in children, but most people will get chickenpox at some point in their lives if they have not had the chickenpox vaccine.

Chickenpox usually isn't serious in healthy children. But it can cause problems for pregnant women, newborns, teens and adults, and people who have immune system problems that make it hard for the body to fight infection.

After you have had chickenpox, you are not likely to get it again. But the virus stays in your body long after you get over the illness. If the virus becomes active again, it can cause a painful viral infection called shingles.

What causes chickenpox, and how is it spread?

Chickenpox is caused by the varicella-zoster virus. It can spread easily. You can get it from an infected person who sneezes, coughs, or shares food or drinks. You can also get it if you touch the fluid from a chickenpox blister.

A person who has chickenpox can spread the virus even before he or she has any symptoms. Chickenpox is most easily spread from 2 to 3 days before the rash appears until all the blisters have crusted over.

You are at risk for chickenpox if you have never had the illness and have not had the chickenpox vaccine. If someone you live with gets chickenpox, your risk is even higher because of the close contact.

What are the symptoms?

The first symptoms of chickenpox often are a fever, a headache, and a sore throat. You or your child may feel sick, tired, and not very hungry. The chickenpox rash usually appears about 1 or 2 days after the first symptoms start. Some children get the chickenpox rash without having a fever or other early symptoms.

It usually takes 14 to 16 days to get the symptoms of chickenpox after you have been around someone with the virus. This is called the incubation period.

After a chickenpox red spot appears, it usually takes about 1 or 2 days for the spot to go through all its stages. This includes blistering, bursting, drying, and crusting over. New red spots will appear every day for up to 5 to 7 days.

You or your child can go back to work, school, or day care when all blisters have crusted over. This is usually about 10 days after the first symptoms start.

Other illnesses can have symptoms like those of chickenpox. For this reason, you may think you have had chickenpox twice when instead you have had two different infections.

How is chickenpox diagnosed?

Your doctor will ask you about your symptoms and will examine you. This usually gives your doctor enough information to find out if you have chickenpox.

Healthy children with chickenpox symptoms may not need to visit a doctor. You may be able to describe your child's symptoms to the doctor over the phone. Then your child won't have to leave the house and risk spreading the virus to others. But it is important to check with your doctor to find out if he or she wants to see your child.

Teenagers, adults, pregnant women, and people with health problems need to see a doctor for chickenpox. This is especially important for pregnant women, since chickenpox during early pregnancy can cause birth defects. Call first to make an appointment and to discuss whether you need to take any steps to avoid spreading the virus when you arrive. For example, office staff may take you straight to an exam room, rather than have you wait in the lobby.

How is it treated?

Most healthy children and adults need only home treatment for chickenpox. Home treatment includes resting and taking medicines to reduce fever and itching. You also can soak in oatmeal baths to help with itching.

People with long-term diseases or other health problems may need more treatment for chickenpox. They may need immunoglobulin treatment (IG) or antiviral medicine. Your doctor can give you these soon after you are exposed to the virus to help you feel better sooner.

How can you prevent chickenpox?

You can prevent chickenpox by getting the chickenpox (varicella) vaccine. Doctors recommend two doses of this shot for healthy children 12 months of age and older who have not had chickenpox. Older children and adults who have not had chickenpox and have not yet had the vaccine also need two doses.

Most children do not have a reaction from the vaccine. But if your child has a serious or long-term illness, talk to your doctor about whether your child should have the vaccine. These children may have a bad reaction from the vaccine.

If you have been around a person who has the virus and you have not had chickenpox or the vaccine, you still may be able to prevent the illness. Get a shot of chickenpox antibodies or the vaccine right away.

In rare cases, people who have had the vaccine still get chickenpox. And a few people who have already had chickenpox get it again. If this happens, a milder form of the illness usually occurs, with fewer blisters and symptoms. This is called a breakthrough infection.

Do not expose your child to chickenpox on purpose. Some parents expose their children to chickenpox because they think it is safer for children to have the illness when they are young. But this isn't a good idea, because even young children can have serious problems from chickenpox.

Frequently Asked Questions

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	Chickenpox: Controlling the itch

Cause

The varicella-zoster virus, one of the herpes viruses, causes chickenpox infection. The same virus that causes chickenpox also causes shingles. For more information on shingles (herpes zoster), see the topic Shingles.

How it is spread

The chickenpox virus can spread easily from one person to another. It most often spreads through the respiratory tract, such as mucous membranes of the mouth and nose. You also can get chickenpox through the air, from an infected person's sneezing or coughing. Less often, chickenpox is spread when fluid from a chickenpox blister gets on your skin. Chickenpox is most contagious from 2 to 3 days before the rash develops until all the blisters have crusted over.

On rare occasions, a person can get chickenpox from the fluid of shingles blisters.

Symptoms

The incubation period-the time from exposure to the chickenpox virus until you develop symptoms-is usually 14 to 16 days but can be from 10 to 21 days. The first symptoms of chickenpox infection include:

• A fever of 100.4 °F (38 °C) to 103 °F (39.4 °C).
• Feeling sick, tired, and sluggish.
• Little or no appetite.
• Headache and sore throat.

The first symptoms are usually mild in children, but they can be severe in teens and adults. These symptoms may continue throughout the illness.

About 1 or 2 days after the first symptoms of chickenpox appear, an itchy rash develops. During a typical course of chickenpox:

• Red or swollen spots or bumps appear and turn into pimplelike blisters filled with clear or cloudy fluid.
• The blisters break open, often leaking fluid.
• A dry crust forms over the broken blisters as they heal.

Chickenpox is most contagious from 2 to 3 days before the rash develops until all the blisters have crusted over.

Other conditions may cause a similar rash.

What Happens

The first symptoms of chickenpox-fever, feeling sick, decreased appetite, headache, cough, and sore throat-usually develop between 14 and 16 days after contact with a person infected with the virus. However, it may be as late as 21 days after contact before symptoms appear.

• Some children develop the chickenpox rash without first having the early symptoms.
• Babies 6 months old and younger may have some protection against chickenpox from antibodies passed on by their mothers. If they are infected with the virus, they may not have many symptoms.
• People with impaired immune systems may develop the first symptoms of chickenpox sooner than the usual 10 to 14 days after exposure.

Chickenpox rash usually appears on the upper body about 1 or 2 days after the first symptoms develop. The trunk usually is most affected, the arms and legs the least. The rash also may spread to the scalp, face, nose, and mouth. In rare cases, it spreads into the eyelid lining (conjunctiva), into the clear covering over the eye (cornea), inside the throat, or into the genital area.

It takes about 1 or 2 days for a chickenpox red spot (macule) to go through all its stages, including drying and crusting over. New red spots continue to develop every day for as long as 5 to 7 days.

Skin infection is the most common complication for children under age 5. Skin infection can develop after scratching the rash, which allows bacteria from the skin or under the fingernails to get into a chickenpox blister. This condition can become serious if it is not treated. An infected blister also may develop into a scar.

Some people may have more chickenpox blisters and longer-lasting symptoms than healthy children. Severe illness or complications are more common in:

• Infants after infection of the mother. Babies born within a few days of their mothers' chickenpox infection have a risk of severe chickenpox infection. Babies born to women who had chickenpox in the first or early second trimester of pregnancy may develop congenital varicella syndrome, which can cause birth defects such as eye problems or an underdeveloped limb.
• Pregnant women, who are at risk for premature labor and varicella pneumonia.
• People age 13 and older (especially people who smoke cigarettes or have long-term lung diseases).
  • The most common complication in older children is acute cerebellar ataxia, which causes temporary problems with muscle coordination.
  • In adults, varicella pneumonia is the most common serious complication.
• People with impaired immune systems.
• People who have cystic fibrosis, which causes problems with the lungs and other organs.
• Children and adolescents receiving long-term aspirin therapy.

The varicella-zoster virus that causes chickenpox can appear in different forms. These variations of chickenpox are most often seen in young children and in the fetus of a pregnant woman.

Although you become immune to the chickenpox virus after you have had chickenpox, the virus will still be in your body. The virus can later cause shingles (herpes zoster), usually when you are an older adult. About 15% of people who have chickenpox will later develop shingles.¹

What Increases Your Risk

You are at risk for chickenpox if you have not had chickenpox or the vaccine and you:

• Live with someone who has chickenpox.
• Work or play indoors for more than 1 hour with someone who has chickenpox.
• Are in the hospital and share a room with someone who later develops chickenpox or are cared for by a staff member who later develops chickenpox.
• Have an impaired immune system.

Your risk of getting chickenpox is especially high if you are exposed to a household member with chickenpox, because of the close contact. In addition, you may develop a more severe case than the person who infected you. Chickenpox is most contagious from 1 to 2 days before the rash appears until the blisters have dried and formed crusts.

Some people also are at increased risk of developing complications from chickenpox, such as newborns, teenagers, adults-especially pregnant women-and those with impaired immune systems.

After you have had chickenpox or the vaccine, you become immune to the virus. It is possible that you may have a slight reaction after reexposure, such as a few spots and a slight fever. But you are not likely toget chickenpox more than once.

When To Call a Doctor

Call your health professional immediately if you or your child with chickenpox develops:

• A severe headache or constant vomiting, sensitivity to bright light, or unusual sleepiness or confusion. These may be signs of inflammation of the brain (encephalitis).
• Problems breathing or persistent coughing. These may be signs of varicella pneumonia.
• Red, warm, and sore skin, or if the chickenpox rash changes to bigger open sores. These may be signs of serious skin infection.

Call your health professional if you or your child with chickenpox has any of the following:

• A fever of more than 102 °F (38.9 °C) that lasts longer than 2 days
• Severe itching that cannot be relieved by home treatment
• Chickenpox rash on the eyeball
• A rash that lasts longer than 2 weeks

If you are older than age 12 and have not had chickenpox or don't know if you have had chickenpox or the chickenpox vaccine, call your doctor if you have been in contact with someone who has chickenpox. This is especially important for pregnant women and for people with impaired immune systems, no matter what age they are.

If you or your child has chickenpox, call your doctor before you go into the office to make an appointment and to discuss whether you should take any precautions when you arrive to avoid spreading the infection. For example, office staff may take you directly to an examination room upon your arrival rather than have you wait in the lobby.

Watchful Waiting

Watchful waiting is a wait-and-see approach. If you know that you or your child has been in contact with someone who has chickenpox, watch for the first symptoms (such as fever, feeling sick, decreased appetite, headache, cough, and sore throat). These symptoms usually appear between 14 and 16 days after contact with the infected person. Call your health professional as soon as symptoms or signs appear.

Who To See

The following health professionals can diagnose and treat chickenpox:

• Family medicine physician
• Pediatrician
• Nurse practitioner
• Physician assistant

If severe complications develop, you may be referred to a specialist. For example, you may see a pulmonologist for lung problems. But most healthy children and adults do not develop serious complications from chickenpox.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

Chickenpox (varicella) usually can be diagnosed by the appearance of the chickenpox rash . For healthy children, describing the rash over the phone to a health professional (rather than visiting the office) may be all that is needed.

But some people need to see a health professional when symptoms of chickenpox appear. You are at more risk for complications from chickenpox if you are a teenager, adult (especially if you smoke cigarettes or have a long-term lung disease), or a pregnant woman, or you have an impaired immune system.

If you visit your health professional's office, chickenpox is diagnosed by medical history and physical exam.

Viral tests can determine whether you are immune to the virus and are unlikely to get chickenpox.

If you have a blistering rash and it's not known if it was caused by the chickenpox virus, other tests can be done.

A woman who has chickenpox early in her pregnancy may want to have her fetus checked for birth defects. This can be done with a fetal ultrasound.

Early Detection

There is no general screening for immunity against chickenpox at this time. Most people in the United States had chickenpox as children and have immunity against it.

Some people may be required to be tested for chickenpox immunity. These include people who work in hospitals, day care centers, schools, and other areas where chickenpox can easily be passed from one person to another. Many states now require that children entering day care and school have the chickenpox vaccine (What is a PDF document?) unless they have a doctor's diagnosis or blood test results that prove immunity.

If you are more likely to get severely ill from chickenpox or to have complications of chickenpox, you also need to be tested to confirm whether you have ever had chickenpox and have immunity against it. These people include:

• People with impaired immune systems.
• Women who are able to have children. Women who are pregnant or who want to become pregnant should consider being tested to see whether they have chickenpox immunity. Having chickenpox immunity prevents complications of chickenpox during pregnancy.

If you have never had chickenpox and therefore do not have immunity against it, you may choose to get the chickenpox vaccine (Varivax). Talk with your health professional about the risks and benefits of the chickenpox vaccine.

Treatment Overview

Treatment for chickenpox (varicella) depends on a person's age, health, and severity of the illness.

• Healthy children with chickenpox may need only home treatment. This includes taking acetaminophen (such as Tylenol) or ibuprofen (such as Advil) to reduce fever and discomfort. If you are not sure about the amount of medicine to give your child, talk to your doctor or pharmacist. (Do not give aspirin to people younger than 20 because of the risk of Reye's syndrome).
• Over-the counter oral antihistamines may help reduce itching. But check with your child's doctor before giving them to your child. Oatmeal baths and soothing lotions that don't contain antihistamines may also help. Examples of lotions to use include calamine lotion or Aveeno.
• Healthy teens and adults with chickenpox usually have more severe symptoms than children and are at higher risk for complications than children. Still, most need only home treatment. All teens and adults with chickenpox should be seen by a health professional; some may need hospital care.
• Pregnant women and people with immune system problems are also at increased risk for complications. They should see a health professional immediately if they suspect they have chickenpox.

Getting a shot of chickenpox antibodies may help delay or prevent a person from having chickenpox. And sometimes antiviral medicines are given to shorten the length of the illness.

If you have not had chickenpox or the chickenpox vaccine and you think you've been exposed to the virus, you may be able to get the chickenpox vaccine (What is a PDF document?) . This may prevent you from having the illness or make the illness milder. It is recommended that the vaccine be given within 3 days after exposure to chickenpox. If you can't get the shot within 3 days, getting it up to 120 hours (5 days) after exposure may still help.²

Prevention

Chickenpox (varicella) is a common contagious illness caused by a type of herpes virus. You can prevent chickenpox by getting the chickenpox (varicella-zoster) vaccine (What is a PDF document?) . The vaccine is recommended for:

• All healthy children 12 months of age and older who have not had chickenpox. It is given in 2 doses: the first at 12 to 15 months and the second at 4 to 6 years. (The second dose may be given earlier if it's been at least 3 months since the first dose.) The vaccine can also be given in a single shot that also contains the vaccines for measles, mumps, and rubella. This combination shot is known as MMRV (ProQuad) and can be substituted for one or both of the regular measles, mumps, and rubella (MMR) shots. (Immunization with MMR combination vaccine is recommended for children between 12 to 15 months of age and again at 4 to 6 years of age.)
• Children who have completed their routine immunizations but have not had chickenpox. Many states require that children entering day care and school have the vaccine unless they show proof of immunity (doctor's diagnosis or blood test results).
• Teens and adults who have not had chickenpox.
• People who do not know whether they had chickenpox as a child. It is safe for them to receive the chickenpox vaccine even if they had chickenpox in the past.
• People who have not had chickenpox or the vaccine and have been exposed to someone ill from the virus.

Most health organizations recommend the chickenpox vaccine. It provides about 95% protection from moderate or severe infection and 70% to 90% protection against mild infection.² In rare cases, people who have had the vaccine still get chickenpox. If this happens, you will probably get a milder form of the illness, with fewer blisters and symptoms. This is called a breakthrough infection. Talk with your doctor if you have questions or concerns about the vaccine. For more information on routine immunizations, see the topic Immunizations.

You also can prevent chickenpox by having a shot of chickenpox antibodies soon after exposure to the virus. If you have been in contact with a person who has chickenpox and are not sure whether you are immune, talk with your health professional about whether you should have either the chickenpox vaccine or antibodies.

You can help prevent chickenpox by avoiding close contact with people infected with the virus. This is particularly important if you have an impaired immune system. But the virus can spread from an infected person even before symptoms develop. Chickenpox spreads quickly among people who are in close contact with each other in confined spaces, such as children in small classrooms or people who share bedrooms. It may be difficult to prevent chickenpox from spreading after the rash develops.

Women who want to become pregnant and have never had chickenpox should consider being tested for immunity or get the vaccine to prevent complications of chickenpox during pregnancy.

Don't expose children to chickenpox

Parents should not intentionally expose children to chickenpox. Some parents hold "chickenpox parties" to expose their children to children who have the illness, believing it is safer for them to have the infection when they are younger than when they are older. This is not a good idea because even young children can have serious (though rare) complications from the infection, including pneumonia or encephalitis. Also, it is not possible to know which children will develop complications.

Prevent the spread of chickenpox

If you or your child has chickenpox, don't return to work, school, or day care until after all blisters have crusted over, usually about 10 days after the first symptoms start. To help prevent spreading chickenpox, stay away from people who aren't immune.

Home Treatment

Most healthy children, teens, and adults with chickenpox (varicella) need only home treatment. But all teens and adults with chickenpox need to see a doctor. Call first to make an appointment and to discuss whether you need to take any steps to avoid spreading the virus when you arrive. For example, office staff may take you straight to an exam room, rather than have you wait in the lobby.

If you have chickenpox, you do not need to stay in bed, but you should stay quiet and rest. You can take oral over-the-counter medicines to treat symptoms such as fever and itching. Before giving medicine to your sick child, check with your child's doctor. Because of their small size, children are more sensitive than adults to the effects of some medicines. Use a measuring spoon or medicine cup to give liquid medicine to a child; do not guess the amount or use a regular table spoon.

Reduce itching

The chickenpox rash itches. Scratching the blisters may cause a skin infection or scars to form after the blisters heal. You can take steps at home to control itching, such as taking oatmeal baths, applying cool compresses, and taking antihistamines by mouth. Check with your child's doctor before giving your child antihistamines.

Monitor fever

Fever is your body's normal response to infection. A higher-than-normal temperature kills bacteria and viruses that cause illness. Medicines that reduce fever stop this natural process, so they should be used only as needed. If a child with chickenpox does not act sick or complain of symptoms, you may choose not to give medicine for fever. Call your health professional if your child's fever lasts longer than 48 hours. You can help reduce a fever by using nonprescription medications and drinking cool liquids. If you are not sure about the amount of medicine to give your child, talk to your doctor or pharmacist. (Do not give aspirin to people younger than 20 because of the risk of Reye's syndrome).

Prevent the spread of infection

Chickenpox can spread easily from one person to another. If you have frequent and close contact with a person infected with chickenpox, such as a family member, you may be exposed to a large amount of the virus. As a result, you may develop a more severe illness than the person who spread it. You also may be at greater risk for complications from the illness, especially if you have an impaired immune system. To prevent the spread of chickenpox, you or your child should stay home from work or school when ill.

Medications

Most people can get the chickenpox shot (vaccine) to prevent chickenpox. The shot doesn't fully protect you right away. But you'll become immune to the virus with a little time. If you get the shot within 3 days after you were exposed to the virus, you may prevent or at least get a milder case of chickenpox.

Most people don't get chickenpox more than once. But it's possible to have a mild case, such as a few spots and a slight fever, if you're exposed to the virus again.

Antiviral medicines also may be an option after you start to develop symptoms of chickenpox. These medicines do not prevent or cure chickenpox, but they can help shorten its course and make it milder.

Immunoglobulins can be given to help protect you from getting chickenpox after you have been exposed to it. However, these medicines can give only short-term protection (up to 3 months).

After you have developed symptoms of chickenpox, you can use oral over-the-counter medicines to help relieve discomfort. Check with your child's doctor before giving medicine to your child.

Medication Choices

Vaccination to prevent chickenpox

To prevent chickenpox, most people can get the varicella-zoster vaccine (Varivax) (What is a PDF document?) before exposure to the virus.

• Two doses of Varivax are routinely given at 12 to 15 months and 4 to 6 years of age. Adolescents and adults who are not already immune can get two doses at least 4 weeks apart.
• Children age 12 and younger can substitute the MMRV (ProQuad) shot instead of getting separate shots for chickenpox, measles, mumps, and rubella.³

Talk to your child's doctor about whether your child should get Varivax or the combination shot.

If you are exposed to chickenpox and you get the vaccine within 72 hours (3 days), you may not get sick or your illness may be mild. If you can't get the shot within 3 days, getting it up to 120 hours (5 days) after exposure may still help.² Some people can't get the chickenpox vaccine, including women who are pregnant and people who have ever had a serious allergic reaction to gelatin or the drug neomycin.

Medications to help decrease the severity of chickenpox

• Antiviral medicines, such as Zovirax, Foscavir, Famvir, Valtrex, and Denavir. Antiviral medicine is usually used to treat adults and people with impaired immune systems; healthy children usually don't need antiviral medicine when they have chickenpox. It is not known whether antiviral medicines reduce a person's chances of developing complications of chickenpox.
• Immunoglobulins (IG). This treatment is given through a vein, usually at the hospital. Immunoglobulins help the body's immune system recognize and destroy harmful bacteria and viruses in the body, such as the varicella virus. IG can be given to pregnant women or people with certain immune system deficiencies to prevent infections. Immunoglobulin is usually taken from the blood of people recovering from an illness. For example, the IG given to help prevent chickenpox infection is called VariZIG (or VZIG). It is taken from the blood of people who are recovering from chickenpox. If you get VariZIG or IG within 96 hours (4 days) of being exposed to an infected person, it can help make your illness milder or may prevent you from getting ill. If you notice signs of chickenpox infection in the 3 to 4 weeks after you've been exposed, call your doctor. The protection provided by an immunoglobulin injection lasts about 3 months. Immunoglobulin for chickenpox must be given before a rash appears.

Medications to relieve pain and discomfort from chickenpox

• Acetaminophen (such as Tylenol) or ibuprofen (such as Advil) to control pain and fever. If you are not sure about the amount of medicine to give your child, talk to your doctor or pharmacist. People over age 20 also can take aspirin to reduce fever. Do not give aspirin to anyone younger than 20 because of the risk of Reye's syndrome.
• Oral antihistamines to relieve itching, such as Benadryl or Vistaril. Talk to your doctor before using any antihistamine lotions or creams on yourself or your child. And check with your child's doctor before giving antihistamine pills to your child.

What To Think About

Vaccinations to prevent chickenpox help you or your child avoid an illness that causes discomfort, missed work or school, and possibly complications.

In rare cases, you or your child will develop a mild rash after having the chickenpox vaccine. If this occurs, it is best to stay away from other people who have not had chickenpox or the vaccine. When the rash is gone and all blisters have dried and crusted over, you are no longer potentially contagious.

When you use medications to treat symptoms of chickenpox, follow instructions carefully. It is especially important to use care when giving prescription and nonprescription medicines to newborns and small children. If you need to, you can use soothing, non-antihistamine lotions (such as calamine or Aveeno), but talk to your doctor before using any other skin products for itching.

Your health professional may prescribe antibiotics to you or your child if you develop a skin infection from chickenpox blisters.

Surgery

There is no surgical treatment for chickenpox.

Other Treatment

There are no other treatments for chickenpox.

Other Places To Get Help

Organizations

Related Information

• Blisters
• Fever, Age 3 and Younger
• Fever, Age 4 and Older
• Immunizations
• Rash, Age 11 and Younger
• Rash, Age 12 and Older
• Skin Changes

References

Citations

1. Gershon AA (2004). Varicella-zoster virus. In R Feigin et al., eds., Textbook of Pediatric Infectious Diseases, 5th ed., vol. 2, pp. 1962-1971. Philadelphia: Saunders.

2. American Academy of Pediatrics (2006). Varicella-zoster infections. In LK Pickering, ed., Red Book: 2006 Report of the Committee on Infectious Diseases, 27th ed., pp. 711-725. Elk Grove Village, IL: American Academy of Pediatrics.

3. A second dose of varicella vaccine (2006). Medical Letter on Drugs and Therapeutics, 48(1244): 80.

Other Works Consulted

• Habif TP, et al. (2005). Varicella (chicken pox) section of Viral infections. In Skin Disease: Diagnosis and Treatment, 2nd ed., pp. 204-209. Philadelphia: Elsevier Mosby.

• Centers for Disease Control and Prevention (2006). A new product (VariZIG(TM)) for postexposure prophylaxis of varicella available under an investigational new drug application expanded access protocol. MMWR, 55(8): 209-210. Also available online: http://www.cdc.gov/mmwr/PDF/wk/mm5508.pdf.

• Centers for Disease Control and Prevention (2007). Prevention of varicella: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR, 56(RR-4): 1-48. Also available online: http://www.cdc.gov/mmwr/PDF/rr/rr5604.pdf.

• Gershon AA, et al. (2008). Varicella vaccine. In SA Plotkin et al., eds., Vaccines, 5th ed., pp. 915-958. Philadelphia: Saunders Elsevier.

• Hirsch MS (2007). Herpesvirus infections. In DC Dale, DD Federman, eds., ACP Medicine, section 7, chap. 26. New York: WebMD.

• Mohsen AH, McKendrick M (2003). Varicella pneumonia in adults. European Respiratory Journal, 21(5): 886-891.

• Strauss SE, et al. (2008). Varicella and herpes zoster. In K Wolff et al., eds., Fitzpatrick's Dermatology in General Medicine, 7th ed., vol. 2, pp. 1885-1898. New York: McGraw-Hill.

• Swingler G (2007). Chickenpox, search date March 2007. Online version of BMJ Clinical Evidence (12).

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