Chickenpox is very contagious, and can spread from person to person in several ways. It can pass through direct contact when touching a chickenpox blister, the fluid inside a blister, or the saliva of someone with chickenpox. Chickenpox can also spread through the air. The virus can stay in the air for a long time after someone coughs or sneezes, and infect people who breathe that air. Symptoms usually appear 10 to 21 days after exposure to the virus.
A person becomes contagious one to two days before the rash appears. This means that people can spread the virus before they know they are infected. The virus continues to spread until all of the blisters have crusted over.
Healthy people who have had chickenpox do not normally get it again, and are considered protected from the virus.
Vague symptoms of headache and mild fever often occur one to two days before the rash. The rash is red and itchy. It changes from red spots to fluid-filled blisters (called vesicles) that then crust over. New blisters come as old ones crust over, so different stages of the rash are seen at the same time. The rash can involve the whole body, including blisters inside the nose, mouth, eyelids, rectum and vagina. The number varies, but typically there are around 200 to 500. Most blisters crust over after about six days. They generally heal fully after about 20 days.
Chickenpox is usually a mild disease. However, complications can occur, especially in people over age 12 and those whose immune (defence) systems are weakened. Complications of chickenpox include bacterial infection of the blisters, pneumonia, and inflammation of the brain (encephalitis).
Chickenpox infection during pregnancy, especially early in pregnancy, is very concerning. The virus can affect the unborn baby, potentially causing serious birth defects. It is also worrying when a mother develops chickenpox infection between five days before to two days after her baby is born. Chickenpox can cause very severe infections in newborns.
After recovery from chickenpox, the virus can remain dormant (inactive) in a person's nerve roots. It can become active many years later, causing shingles. Shingles occurs most commonly in people over age 50 and in those with weakened immune systems. Like chickenpox, shingles usually produces a red blistering rash. The shingles rash is usually painful, not itchy. It typically affects a smaller area of the body. A common complication is continuing pain in the affected area after the rash disappears, called post-herpetic neuralgia. (Search website for shingles).
The chickenpox rash is very itchy. The itching can interfere with sleep. Scratching can damage the skin, and increases the risk of infections and scarring. To care for healthy young children with chickenpox, controlling symptoms is key. Limit the triggers for itching and take steps to reduce the itch.
Medications that work against the virus, such as the antiviral medication acyclovir, are not recommended to treat chickenpox in healthy young children. However, they may be used in people more likely to develop complications from chickenpox. This includes people over 12 years of age and those with certain medical conditions. Antiviral medications are very useful in treating chickenpox in people with weakened immune systems. They are most effective if started very soon after the rash appears, ideally within one to three days.
Those at higher risk of complications from chickenpox should contact their doctor immediately if chickenpox is suspected. This includes anyone:
Other reasons to contact a doctor include:
Seek medical attention if there are chickenpox lesions on the eyelids or near the eyes or if there is redness of the eye itself (conjunctiva). Immediate medical attention is required if there are signs and symptoms of infection around the brain, including severe headache, stiff neck, confusion, lethargy, or unusual behaviour. If you or your child is diagnosed with chickenpox, your family physician may be required to contact the public health department to monitor varicella activity within the province.
Since people are contagious for about two days before the rash develops, transmission often occurs before you are even aware of the chickenpox. Children can return to daycare or school as soon as they feel well enough to participate in all activities, regardless of the state of the rash.
Until all lesions are crusted over:
Vaccines against chickenpox (varicella vaccines) have been available in Canada since 1998. The chickenpox vaccine is now part of the publicly funded childhood vaccine program in all Canadian provinces and territories. It is routinely given to children between 12 and 18 months of age.
The chickenpox vaccine is about 85 per cent effective at preventing chickenpox infection. It is about 95 per cent effective in preventing severe complications of chickenpox.
The vaccine may prevent disease in those who have been exposed to infectious chickenpox. Remember, this includes those who have never had a chickenpox infection or the vaccination. Get vaccinated as soon as possible after exposure, and certainly within five days. If given within five days of exposure, the vaccine can prevent over 70 per cent of those exposed from developing chickenpox. If chickenpox does develop, it will be mild.
More information about chickenpox can be obtained from several provincial and national health information services:
The vaccine has only been routinely given to infants in Canada for the last four to nine years, depending on where they live. This means many older children and adults who have not had the vaccine or chickenpox are still at risk. The vaccine is recommended for anyone who hasn't had the disease. It is especially important for certain high-risk groups to be immunized, including:
People with very weakened immune systems and pregnant women should not receive the vaccine.
The vaccine is very safe, and serious side effects are rare. The most common reactions are pain and redness at the site of the vaccine injection. About 15 per cent of people have a mild fever. Less than five per cent of people develop a mild chickenpox rash, usually near the injection site.
Though usually mild, chickenpox can have serious complications. If you or your children have never had chickenpox or the vaccine, please contact your local public health centre to see if you qualify for vaccination.