Chickenpox (Varicella)

Overview

Chickenpox (varicella) is an infectious disease which results in a blister-like rash itching tiredness and fever. The rash appears first on the trunk and face but can spread over the entire body causing hundreds of itchy blisters. Most adults today who grew up in Canada had chickenpox as children and recovered completely. In Canada out of 340000 yearly cases of chickenpox only 1800 cases require hospitalization. However severe cases of chickenpox can pose serious health risks especially for newborn babies adults or anyone with a weakened immune system. A vaccine to prevent chickenpox has been available in Canada since 1998.

Causes

Chickenpox is caused by the varicella-zoster virus. It spreads from person to person by direct contact or through the air from an infected person's coughing or sneezing. A person with chickenpox is contagious 1-2 days before the rash appears and until all blisters have formed scabs. It takes from 10-21 days after contact with an infected person for someone to develop chickenpox. A pregnant woman can pass the chickenpox virus on to her baby before it is born.

As a general rule you can only get chickenpox once but it's also possible for the virus to remain in your body and become active again later on. When this happens the virus causes a painful rash of blisters called shingles.

Symptoms

The first symptoms appear between 10 and 21 days after exposure to the varicella virus and may include:

  • aches
  • fever
  • fatigue
  • irritability
  • sore throat

A rash then appears and develops into as many as 250-500 itchy blisters over the entire body. The rash may even spread into the mouth or other internal parts of the body. After four or five days the blisters dry out and become crusted.

From start to finish chickenpox may last seven to ten days but about 5-10% of previously healthy children will develop complications. Serious complications from chickenpox include bacterial infections which can involve many parts of the body including the skin tissues under the skin bone lungs (pneumonia) joints and the blood. Other serious complications are due directly to the virus infection and include viral pneumonia bleeding problems and infection of the brain (encephalitis).

Certain groups are more likely to have more serious illness with complications. These include adults infants adolescents and people with weak immune systems from either illnesses or from medications such as long-term steroids.

Treatment

Acyclovir (a medicine that works against herpes viruses) is sometimes recommended for people who are more likely to develop serious disease including those with chronic skin or lung disease otherwise healthy people 13 years of age or older and anyone receiving steroid therapy. In order for acyclovir to be effective it must be administered within 24 hours of the onset of the chickenpox rash. People with weakened immune systems from disease or medication should contact their doctor immediately if they are exposed to or develop chickenpox. If you are pregnant and are either exposed to or develop chickenpox you should immediately discuss prevention and treatment options with your doctor.

Also talk to your doctor if:

  • a fever lasts longer than 4 days or rises above 102 F
  • areas of the rash or any part of your body become very red warm tender or is leaking pus (thick discolored fluid) as this may mean there is a bacterial infection
  • the person with chickenpox seems extremely ill
  • is difficult to wake up
  • is confused
  • has difficulty walking
  • has a stiff neck
  • is vomiting repeatedly
  • has difficulty breathing
  • has a severe cough.

Scratching the blisters may cause them to become infected. Therefore keep fingernails trimmed short. Calamine lotion and Aveeno (oatmeal) baths may help relieve some of the itching. Do not use aspirin or aspirin-containing products to relieve your child's fever. The use of aspirin has been associated with development of Reye's syndrome a life-threatening illness that causes swelling of the brain and damages the liver and other organs in the body. Use non-aspirin medications such as acetaminophen.

Prevention

A vaccine for chickenpox was licensed for use in Canada in 1998. It is given by needle and is very safe. The side effects are temporary and usually mild. For example some people have a sore spot or some tenderness where the needle went in. Up to 15% may have a mild fever that lasts for a few days. Up to 6% may develop a rash that resembles a mild case of chickenpox within a week or two of vaccination. The rash will clear up in about five days. Overall these side effects are far less harmful than the potential complications from a serious case of chickenpox.

The National Advisory Committee on Immunization (NACI) recommends the chickenpox vaccine for healthy children (age 12 months and up) teenagers and adults who have not already had chickenpox.

If you have had chickenpox once you do not need to get the vaccine. But a dose of the vaccine is unlikely to cause any harm as long as your overall general health is good.

However NACI advises that certain people should not get the chickenpox vaccine including:

  • people who have a prior history of severe allergic reaction to the vaccine or other components of the vaccine
  • people with weak immune systems unless under the supervision of a specialist in infectious diseases
  • pregnant women or those who are trying to get pregnant
  • babies less than a year old