Chickenpox

Caused by the varicella zoster 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.

infant with chickenpoxMost 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 children turning 15 months of age and children turning 11 years of age who have never been infected with or previously vaccinated against chickenpox. Read more about the chickenpox vaccine.

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 daycare during this time.

Can there be 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 bloodstream 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. The highest risk period is during the first 20 weeks of pregnancy. Up to 2 in 100 infants exposed to chickenpox before birth will be born with congenital varicella syndrome and may have skin scarring, eye, limb and brain abnormalities, developmental delay and a poor outcome. Up to 30 in 100 newborn babies with chickenpox develop severe disease that can result in death. If you’re pregnant and think you have been exposed to chickenpox, you should have a blood test to check whether you’re 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. 

Self care 

  • Applying 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 can dry out the skin.
  • To prevent dehydration, 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 

  • 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.
  •  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 — since 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, and your doctor may prescribe an antibiotic ointment to treat the infection. It is important not to scratch the sores, to prevent infection. 
  • Antiviral medicine may be considered in some adolescents and adults, to reduce the severity of the infection. It should be started within 24 hours of the rash appearing.

Preventing spread of chickenpox 

Chickenpox is spread both through the air, when an infected person 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.

Immunisation

Vaccination against chickenpox is free for children turning 15 months of age and children turning 11 years of age who have never been infected with or previously vaccinated for chickenpox.

Chickenpox vaccination is also recommended, but not funded, for:

  • teenagers and adults who have never been infected with or vaccinated against chickenpox.
  • women who are planning a pregnancy and have never been infected with or vaccinated against chickenpox.
  • people who are not immune to chickenpox and who are working in professions where they come into contact with young children
  • parents who have not had chickenpox.

Read more about the chickenpox vaccine.

Learn more

NZ focused fact sheet Kids Health (NZ), 2014
In-depth 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: Health Navigator Editorial Team.