Chickenpox

Caused by the varicella virus

Chickenpox is a common childhood illness that causes an itchy, blistering rash. Chickenpox is very easily spread. Unless vaccinated against it, most people will catch it when they are children.

Most cases of chickenpox are mild but it can cause more serious illness in adults, during pregnancy and in people with an impaired immune system. Vaccination against chickenpox is free for certain high-risk groups. 

What causes chickenpox?

Chickenpox is caused by the human herpes virus type 3, more commonly known as varicella zoster virus. It is the same virus that can cause shingles, which usually occurs later in life. 

How contagious is chickenpox?

This chickenpox virus is highly contagious, meaning it is very easy to catch. It is spread by sneezing and coughing, or by contact with weeping blisters when the sores are present. You can even catch the chickenpox virus from touching clothing or other objects that have fluid from the blister on them.

My child has been in contact with someone with chickenpox. How long will it take for them to get it?

Generally, the time from infection to appearance of the rash (incubation period) for chickenpox is usually 14 to 16 days but can range from 10 to 21 days. A few days before the first spots appear the person may feel feverish with a sore throat and headache.

A child is infectious 1-2 days before they get the rash until all the blisters have dried up. This usually takes 5 to 7 days.

Who is at risk of getting chickenpox?

You are at risk of getting chickenpox if you are exposed to the chickenpox virus and have never had chickenpox or haven’t had the chickenpox vaccine. In New Zealand about 90% of those who are not vaccinated get chickenpox when they are children.

If one child in your family gets chickenpox, it is highly likely that other children (or anyone in your household who hasn’t had it before) will get it also.

What are the symptoms of chickenpox?

It takes 2 to 3 weeks for symptoms to appear after infection with the virus. At first, a person with chickenpox may have cold-like symptoms, mild headache and a moderate fever.

A few days later, a red and pimply rash follows:

  • The rash normally starts on the face and scalp, and later spreads to other parts of the body – including on the eyelids, the mouth, up the nose and in the genital region.
  • The rash continues to spread for 3 or 4 days.
  • A few hours after each 'pimple' develops, it turns into clear-fluid-filled, blister-like sore.
  • These sores usually become very itchy. 
  • After a day or so, the blisters burst, releasing the virus-containing fluid.
  • Crusts or scabs form and take 1 to 2 weeks to fall off. 
  • The spots heal at different stages, some faster than others, so your child may have the rash in several different stages at once.

Some children have mild chickenpox with under 50 spots; others have a miserable time with hundreds of spots.

Chickenpox is most infectious from two days before the rash is present until after scabs have formed on all the sores and no new sores develop – this takes about seven days. Children with chickenpox need to stay home from school and day care during this time.

Are there likely to be any complications from having chickenpox?

In most children, chickenpox is a mild disease which doesn't cause any lasting problems. Sometimes scarring can occur where the spots have been.

The most common complication is secondary skin infection.

  • Around 1 in 20 healthy children develop a bacterial skin infection.
  • This needs to be treated with antibiotic medicine.
  • Untreated bacterial skin infections can lead to bacterial infection in other parts of the body, including pneumonia and blood stream infection (septicaemia).

Other complications are rare and include:

  • encephalitis (brain inflammation)
  • severe secondary infections needing intensive care
  • inflammation of the joints, kidneys and liver
  • the nervous system can also be affected.

Contact your doctor if the person with chickenpox develops any worrying symptoms, such as:

  • very high fever
  • nausea and vomiting
  • sensitivity to light
  • stiff neck
  • confusion
  • severe headache
  • any difficulty breathing
  • drowsy and hard to wake
  • has fits (seizures)
  • unable to drink due to severe rash in the mouth
  • severe rash that looks infected or a rash which bruises or bleeds into the skin
  • becoming generally more and more unwell.

If you are concerned call Healthline on freephone 0800 611 116 for advice, or contact your doctor.

Chickenpox and pregnancy

There are potential risks for mother and baby if chickenpox occurs during pregnancy. Pregnant women who think they have been exposed to chickenpox should see their doctor to check if they are immune.

What is the treatment for chickenpox

For some people, the rash may be no more than a passing inconvenience, but for others, it can be very unpleasant. Treatment is aimed at controlling the symptoms and supporting your body's immune system to do the rest.

The itch caused by chickenpox can be very irritating and asking your child not to scratch their itch will probably fall on deaf ears. However, it is worth trying to distract them as best you can. Scratching at spots can lead to infection, which in turn can cause scarring. 

Simple measures to soothe itching and prevent scratching 

  • Apply a soothing cream (emollient) such as alpha keri or fatty cream may help soothe the itch. The use of calamine lotion is no longer recommended as it has been found to be too drying.
  • Make sure your child has plenty of clear fluids (water, thin soup, lemonade or ice blocks). Don't worry if they don't eat much while they are sick – this will be fine for a day or two. 
  • Trim fingernails as short as possible and make sure that their hands and fingernails are kept clean. 
  • Use mittens or clean socks on hands to decrease the risk of infection from scratching, especially overnight.
  • Dress your child in loose-fitting clothing and change the bed linen daily.
  • Try giving your child a cool or luke-warm bath. Do not use soap as this will irritate their skin. Add 2 cups ground oatmeal or half a cup of baking soda to make the bath even more soothing. Pat skin dry, do not rub, after bathing. 

Medications used to relieve chickenpox symptoms

  • Paracetamol can be given to help reduce the fever and ease any headaches.
    • Make sure you measure children's doses accurately and follow the directions given on the bottle or product packaging.
  • Aspirin should not be given to children under 16 years as it is associated with the rare but serious Reye's syndrome. 
  • Ibuprofen is not recommended as it may increase the risk of serious skin infection complications in children with chickenpox. 
  •  Antihistamines.
    • If your child is unable to sleep because of the itch, an antihistamine (anti-itch) medication may help. Discuss the best option with your doctor or pharmacist. 
  •  Antibiotics
    • As chickenpox is caused by a virus, antibiotics are not used to treat it. However, if the spots look ‘angry’, red and inflamed they may have become infected.
    • Your doctor will be able to prescribe an antibiotic ointment to treat the infection. 
    • Not scratching at the sores is important in preventing bacterial infection. 
  • Antiviral medicine for teenagers and adults
    • For healthy adolescents and adults, the use of antiviral medicine should be considered in addition to comfort measures.
    • Antiviral medicine started within 24 hours of the rash appearing may reduce the severity of the disease.

Preventing spread of chickenpox 

Chickenpox is spread both through the air, when someone coughs or sneezes, or through contact with the fluid in the blisters.

Chickenpox is most infectious from two days before the rash is present until after scabs have formed on all the sores (and no new sores develop) – this takes about seven days. During this time: 

  • Do not send your child to school or preschool. 
  • Wash hands often and after tending to a child who has chickenpox. 
  • Coughs and sneezes should be kept covered.

For children who have not really been all that sick with chickenpox, staying at home can be a bit annoying. Remember, however, that for some children and adults, chickenpox can be a very serious illness, so it is best to do all you can to stop it spreading.

Can chickenpox be prevented?

Children from 9 months of age can have the chickenpox immunisation.

  • Most people who have this vaccine will not get chickenpox.
  • If an immunised person does get chickenpox, it is usually mild.

In New Zealand, chickenpox immunisation is not part of the national immunisation schedule. The chickenpox vaccine is available from your family doctor, but you may have to pay for it. It’s available free to certain high-risk groups.

People who are not immune to chickenpox who are working in professions where they come into contact with young children, or parents who have not had chickenpox themselves, may wish to consider having the vaccine. 

Read more about the chickenpox vaccination and making the decision to vaccinate.

Learn more

NZ focused fact sheet Kids Health (NZ), 2014
Indepth fact sheet Patient Info, UK, 2014
Fact sheet for kids Centre for Disease Control (US), 2011

References

  1. Fact sheet for healthcare professionals Kids Health (NZ), 2011
  2. Podcast Centre for Disease Control (US) 2008
Credits: Editorial team.