Chicken Pox (Varicella)

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What is it

Varicella is a very contagious disease caused by varicella-zoster virus, a DNA virus of the herpes virus family1,2. 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 vaccination1,4,5. 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 immunization1,4,5. 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.

REFERENCES

  1. Public Health Agency of Canada. Varicella (Chickenpox) (2012). http://www.phac-aspc.gc.ca/im/vpd-mev/varicella-eng.php
  2. Centers for Disease Control and Prevention. Chickenpox (Varicella): About Chickenpox (2016). https://www.cdc.gov/chickenpox/about/index.html
  3. Centers for Disease Control and Prevention. Chickenpox (Varicella): Signs & Symptoms (2016). https://www.cdc.gov/chickenpox/about/symptoms.html
  4. GSK Priorix-Tetra Product Monograph. (2017) https://ca.gsk.com/media/591336/priorix-tetra.pdf
  5. Merck ProQuad Product Monograph (2017) https://pdf.hres.ca/dpd_pm/00037770.PDF
  6. Centers for Disease Control and Prevention. Chickenpox (Varicella): Prevention & Treatment (2016). https://www.cdc.gov/chickenpox/about/prevention-treatment.html