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Varicella, also known as chickenpox, was a common childhood disease occurring worldwide before the varicella (chickenpox) vaccine became widely used. In countries without vaccination programs for chickenpox, 50 per cent of children get the disease before age 5, and 90 per cent get it before age 12. Ontario has had a vaccination program since 2004, resulting in a large decrease in cases.
Chickenpox is caused by the varicella-zoster virus. It spreads through the air when an infected person breathes, coughs, sneezes or talks. People can become infected if they breathe contaminated air or touch contaminated surfaces, then touch their eyes, nose or mouth. The virus can also spread by direct contact with the fluid inside chickenpox blisters.
A person with chickenpox can spread it to others starting one to two days before the rash appears until all the blisters have dried and formed scabs. Chickenpox cases are usually more common during the school year and less common over the summer.
Symptoms usually start between 14 to 16 days after exposure but can start anywhere between 10 to 21 days after exposure.
Symptoms include:
In healthy children, chickenpox can be relatively mild. However, complications can still happen including pneumonia (lung infection), blood and skin infections or swelling of the brain. An infection during pregnancy can cause serious illness for the baby. Newborns, infants or people with a weakened immune system can also get very ill.
Many years after a chickenpox infection, a painful rash can occur, called herpes zoster or shingles.
Vaccination against chickenpox is very safe and effective.
In Ontario, children receive one dose of the varicella vaccine at 15 months of age, then again as part of the measles, mumps, rubella, and varicella (MMRV) vaccine, which is routinely given at 4 to 6 years of age.
The varicella vaccine is very safe and effective. Most reported side effects are mild, including fever, rash, and injection site reactions. One dose of varicella vaccine provides protection in about 94 per cent of people, and two doses provide over 98 per cent protection.
Learn more about MMR and MMRV Vaccines including the risks associated with vaccination against varicella, vaccination against varicella as part of the MMRV vaccine, people who should avoid or delay vaccination, and people who should be prioritized.
If you or your child(ren) were in close contact with someone with chickenpox, watch for symptoms for 21 days after your last contact with that person.
If you think you or your child might have chickenpox:
Health care providers generally diagnose chickenpox based on the characteristic rash, but if there is any doubt, a blood test, and a test using fluid from blisters, are available to confirm diagnosis. A blood test can be used to find out if someone has chickenpox, recently had it, or is immune to the disease after an infection or vaccination.
Most healthy children do not need treatment. However, medicine may be given to help with itching or fever. To help with chickenpox symptoms at home, you can:
People who are at higher risk of getting very sick from chickenpox may be given antiviral medicine. This medicine can help shorten the illness and lower the risk of serious illness. Antibiotics may be given to people who develop serious illness, such as a skin infection or pneumonia (lung infection).
Talk to your health care provider about treatment options that may be right for you.
If you are not immune to chickenpox, you may need treatment after exposure to the virus. This depends on how much contact you had with the infected person, your age, and your immune system.
Healthy babies less than 12 months usually do not need treatment after exposure because they are often protected by antibodies passed on from their mother.
The following are considered significant exposures to a person with chickenpox:
After exposure, people who are not protected against chickenpox may be offered the chickenpox vaccine (not the MMRV vaccine). The vaccine works best when given within 72 hours of exposure, but it may still be given up to five days later. Another treatment, called varicella immune globulin, may also be recommended in some situations.
Contact your health care provider for advice.
Chickenpox needs to be reported to Toronto Public Health by schools, child care centres and health care providers.
Call Toronto Public Health at 416-338-7600 (TTY at 416-392-0658) or speak to your health care provider. You can also call 811 to connect to a registered nurse day or night for free, secure and confidential health advice.