Varicella (Chickenpox)

How varicella spreads

Varicella spreads through coughing, sneezing and breathing, and through contact with fluid from blisters. About 9 in 10 unvaccinated people living with an infected person will catch it. People are contagious from 1 to 2 days before the rash appears until all blisters have crusted, usually about 5 to 7 days after the rash starts.

People with shingles can spread the virus through contact with their blisters, causing chickenpox (not shingles) in someone who is not immune.

Symptoms and stages

1. Prodrome (1 to 2 days): fever, tiredness, headache, loss of appetite; often mild in children.
2. Spots: small red spots appear, first on the face, scalp, chest and back, then spreading.
3. Blisters: spots become clear, fluid-filled blisters ("dewdrops on a rose petal").
4. Crusting: blisters cloud, break and crust over.
5. New crops appear for 3 to 5 days, so spots at all stages are seen at once.

Spots can occur in the mouth, eyelids and genitals. Itching is often intense. Vaccinated people who get "breakthrough" varicella usually have a milder illness with fewer than 50 spots and little fever.

Complications

More likely in babies, teenagers, adults, pregnant people and those with weakened immunity:

• bacterial skin infections, including impetigo and cellulitis, and rarely invasive group A strep
• pneumonia, especially in adults and smokers
• brain inflammation (encephalitis) and cerebellar ataxia (unsteadiness)
• dehydration
• bleeding problems
• Reye syndrome if aspirin is given
• in pregnancy: severe pneumonia in the mother, and congenital varicella syndrome if infected early in pregnancy; severe newborn infection if the mother develops chickenpox shortly before or after delivery

Shingles later in life

After chickenpox, the virus lies dormant in nerve roots. It can reactivate decades later as shingles, a painful band of blisters. A shingles vaccine is recommended for adults 50 and older.

Diagnosis

Chickenpox is usually diagnosed by the typical rash. PCR testing of blister fluid confirms it in unclear cases or high-risk people. Blood tests for antibodies check immunity, for example in pregnancy.

Treatment

Home care

• fever and pain: acetaminophen (paracetamol) at the label dose. Never give aspirin to children or teenagers. Many experts advise avoiding ibuprofen during chickenpox because of a possible link with severe skin infections.
• itch: calamine lotion, cool baths with colloidal oatmeal or baking soda, and oral antihistamines
• keep fingernails short and consider mittens for young children to reduce scratching
• drink plenty of fluids
• stay home from school, childcare or work until all blisters have crusted

Antiviral treatment

Acyclovir or valacyclovir, started within 24 hours of the rash, is recommended for people at higher risk of complications: teens and adults, people with chronic skin or lung disease, those on long-term steroids or aspirin, pregnant people (as advised), and those with weakened immunity (often IV).

After exposure

• vaccine within 3 to 5 days of exposure can prevent or soften illness in non-immune children and adults
• varicella zoster immune globulin (VZIG) within 10 days for high-risk people who cannot have the vaccine: pregnant people without immunity, newborns of mothers with chickenpox around delivery, and immunocompromised people

Vaccination

• two doses: the first at 12 to 15 months and the second at 4 to 6 years
• older children, teens and adults without immunity need two doses 4 to 8 weeks apart (or at least 3 months apart for children under 13)
• the vaccine is live, so it is not given during pregnancy or to people with severely weakened immunity
• vaccination has greatly reduced chickenpox cases, hospital stays and deaths

Frequently asked questions

What are the first signs of chickenpox?

Often a mild fever, tiredness, headache and loss of appetite for a day or two, followed by small red itchy spots, usually starting on the face, scalp, chest or back, which quickly turn into blisters.

How long is chickenpox contagious?

A person is contagious from 1 to 2 days before the rash appears until all the blisters have crusted over, typically 5 to 7 days after the rash starts.

Is chickenpox worse in adults?

Yes. Adults are more likely to have severe illness and complications such as pneumonia. Adults with chickenpox should see a doctor promptly, as antiviral treatment within 24 hours of the rash helps.

Can you get chickenpox twice?

It is uncommon. Most people are immune for life after chickenpox. The virus can, however, reactivate later as shingles. Vaccinated people can occasionally get a mild breakthrough infection.