Chicken Pox (Varicella)

What is it

Varicella is a very contagious disease caused by varicella-zoster virus, a DNA virus of the herpes virus family^1,2. Following the initial episode of varicella illness, the virus establishes latency in the body’s nerve system, and can be reactivated later in life as herpes zoster which is known as shingles¹.

Who is at risk

Varicella is very common worldwide and in densely populated metropolitan communities¹. Although rates of childhood varicella have been greatly reduced with the implementation of universal childhood immunization programs, a greater number of cases are now occurring in adolescents and adults¹. Some data suggest that people from the tropics are less likely to acquire immunity in childhood and therefore have higher rates of susceptibility as adults¹.

What are the symptoms

Symptoms may take 10 to 21 days to appear post infection¹. Individuals are most contagious from 1 to 2 days before to shortly after the onset of rash¹. The duration of illness is approximately 5 to 7 days and persists until the skin lesions crust over². Initial symptoms include a slight fever, mild headache, runny nose and general malaise¹.

Defining symptoms of varicella¹:

Skin lesions on all areas of body, including the scalp and mucous membranes of the mouth and upper respiratory tract
Fluid-filled lesions
Occurring in “crops”, where old and new lesions can be present at the same time
Severity ranging from mild (a few spots) to severe (concurrent fever and widespread rash)

How is it spread

Varicella is solely a human disease; the virus can be spread by direct contact with fluid in the lesions or through airborne spread from the respiratory tract¹. The attack rate among susceptible contacts in household settings is estimated at 65%-87%¹.

How is it prevented

Varicella can be prevented through vaccination^1,4,5. Most people who get the vaccine will not get chickenpox². If a vaccinated person does get chickenpox, it is usually mild with fewer red spots². The vaccine prevents almost all cases of severe disease. The National Advisory Committee on Immunization (NACI) recommends that healthy children 12 months to 12 years of age should receive two doses of varicella-containing vaccine (univalent varicella or MMRV) for primary immunization^1,4,5. Different vaccines have different dosing schedules. For further information on the various vaccination options, please speak with your healthcare provider

For further information about varicella vaccine and its use in adolescents, adults and special populations, please refer to the most recent version of the Canadian Immunization Guide¹.

People who have or suspect that they have varicella should be reported to the local health authority¹. In addition, isolation can mitigate the spread of illness¹:

Avoid public places for at least 5 days after the first crop of lesions appears
Call ahead before seeing a physician to decrease others’ exposure to varicella in the office
Keep infected children away from school or public places until the last lesions have scabbed over
Wash or disinfect articles that may have been soiled by the vesicle fluid or by any discharge from the nose or throat
Contacts, especially children, must have their immunization status verified
Necessary doses of vaccine should be given if immunization status is incomplete

How is it treated

Symptoms of varicella can be alleviated with the following⁶:

Calamine lotion or colloidal oatmeal baths – to relieve itching
Oral analgesics, such as acetaminophen – to relieve fever and pain
- Note: do not use aspirin or aspiring-containing products to relieve fever from chickenpox. Its use in children with chickenpox has been associated with Reye’s syndrome, a severe disease affecting the liver and brain and potentially causing death.

Keeping fingernails trimmed short may help prevent skin infections caused by scratching blisters.

Antiviral medications may be prescribed by the healthcare provider for people with varicella who are more likely to develop serious disease including:

Otherwise healthy people older than 12 years of age
People with chronic skin or lung disease
People receiving steroid therapy
Pregnant women

Medical advice is recommended for the onset of chicken pox-like symptoms. For further information regarding chicken pox and immunization, please speak with your healthcare provider.

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