Chickenpox (Varicella)

How chickenpox spreads

Chickenpox spreads easily through coughs, sneezes and breathing in virus from the air, and by touching fluid from blisters. About 9 in 10 people without immunity who live with someone with chickenpox will catch it. People with shingles can also spread the virus, causing chickenpox in non-immune people, but only through contact with the blisters.

Symptoms and stages of chickenpox

Before the rash

One to 2 days of mild fever, tiredness, headache, loss of appetite and aching. In young children the rash is often the first sign.

Stages of the rash

New crops appear for 3 to 5 days, so spots, blisters and scabs are seen together. The rash usually starts on the chest, back and face and spreads to the whole body, including the scalp, inside the mouth, the eyelids and the genital area. Most children have 250 to 500 spots.

Breakthrough chickenpox

Vaccinated people sometimes catch chickenpox. It is usually much milder, with fewer than 50 spots, mostly red bumps rather than blisters, and little or no fever. It is still contagious.

Who is at risk of severe chickenpox

• babies, particularly newborns whose mothers had chickenpox around delivery
• teenagers and adults
• pregnant women, who risk pneumonia; infection in early pregnancy can rarely cause birth defects, and near delivery can cause severe newborn infection
• people with weakened immune systems from leukemia, cancer treatment, organ transplants, high-dose steroids or HIV
• people with eczema or other skin conditions, who can get more widespread rashes

Complications

• Bacterial skin infection of scratched blisters, including cellulitis and, rarely, invasive group A strep infection
• Pneumonia, especially in adults, smokers and pregnant women. See pneumonia.
• Brain involvement: cerebellar ataxia (unsteady walking, usually recovers) or encephalitis
• Dehydration from poor drinking
• Reye syndrome if aspirin is given to a child with chickenpox. See Reye syndrome.
• Scarring, especially from scratched or infected spots
• Shingles later in life

Diagnosis

Chickenpox is usually diagnosed from the typical rash. A swab of a blister for PCR testing confirms it when the diagnosis is uncertain, in high-risk people, or in vaccinated people with atypical rashes. Blood tests can check immunity after exposure, for example in pregnancy.

Treatment

Home care

• Fever and pain: acetaminophen (paracetamol) at the label dose. Never give aspirin to children or teenagers, because of Reye syndrome. Many clinicians advise avoiding ibuprofen during chickenpox because it has been linked with severe skin infections; ask your doctor or pharmacist.
• Itching: cool baths with colloidal oatmeal or baking soda, calamine lotion, and an oral antihistamine (follow the label and age limits).
• Prevent scratching: keep nails short, use mittens on babies at night, and dress in loose cotton clothes.
• Fluids: offer drinks often; cold, soft foods help if the mouth is sore.
• Mouth sores: avoid salty or acidic foods.

Antiviral medicine

Acyclovir or valacyclovir can shorten illness and reduce complications when started within 24 hours of the rash. They are recommended for people at higher risk: those over 12, people with chronic skin or lung disease, people on long-term steroids or aspirin therapy, pregnant women in some cases, and anyone immunocompromised (often IV).

After exposure in high-risk people

Non-immune pregnant women, newborns and immunocompromised people exposed to chickenpox may be given varicella-zoster immune globulin, ideally within 10 days. Non-immune healthy people over 12 months can be vaccinated within 3 to 5 days of exposure to prevent or soften illness.

How long chickenpox is contagious

People are contagious from 1 to 2 days before the rash appears until every blister has crusted over, usually 5 to 7 days after the rash begins. Keep children home from school or child care until all spots have scabbed. Avoid contact with pregnant women, newborns and immunocompromised people during this time.

Prevention: the chickenpox vaccine

• The CDC recommends two doses: the first at 12 to 15 months and the second at 4 to 6 years.
• Older children, teenagers and adults without evidence of immunity should get two doses at least 4 weeks apart (at least 3 months apart for children under 13).
• Two doses are about 90 percent effective at preventing chickenpox and even more effective at preventing severe disease.
• It is a live vaccine and is not given during pregnancy or to people with severely weakened immune systems.

Since vaccination began in the US in 1995, chickenpox cases, hospital stays and deaths have fallen dramatically.

Chickenpox and shingles

After chickenpox, the virus remains dormant in nerve cells. Years later it can reactivate as shingles, a painful, one-sided band of blisters, most often after age 50. Shingles vaccine is recommended for adults 50 and older.

Frequently asked questions

What are the first signs of chickenpox?

The first signs are often mild fever, tiredness, headache and loss of appetite for a day or two, followed by small red itchy spots, usually on the chest, back or face. Within hours, the spots turn into fluid-filled blisters, and new crops keep appearing for several days.

How long is chickenpox contagious?

Chickenpox is contagious from 1 to 2 days before the rash appears until all blisters have crusted over, typically 5 to 7 days after the rash starts. Children can return to school once every spot has scabbed and no new spots are appearing.

Is chickenpox worse in adults?

Yes. Adults usually have more spots, higher fever and a longer illness, and are much more likely to develop pneumonia and other complications. Adults with chickenpox should contact a doctor promptly, as antivirals work best within 24 hours of the rash.

Can you get chickenpox twice?

It is uncommon but possible, particularly if the first infection was very mild or happened in early infancy. Vaccinated people can get mild breakthrough chickenpox. Most people have lifelong immunity after one infection.

Can I give my child ibuprofen for chickenpox?

Many doctors advise using acetaminophen (paracetamol) instead, because ibuprofen has been linked with severe skin infections in chickenpox. Never give aspirin to children or teenagers with chickenpox, because of the risk of Reye syndrome. Ask your doctor or pharmacist if unsure.