varicella

Also see the topic on Shingles

What is chickenpox?

Chickenpox is a highly infectious disease, which mostly affects children. It is generally a mild disease, which does not last long in healthy children, but may cause serious illness or death in people who have a lowered immunity. Adults who develop chickenpox become generally unwell with a 'flu-like' illness. The severity of disease and the risk of complications in adults and adolescents are usually greater than in children. Chickenpox also has potential risks for mother and baby if it occurs in pregnancy.

What causes it?

Chickenpox is caused by the varicella-zoster virus, also known as human herpes virus type 3. This virus is present in large numbers in and behind the nose, and is spread from child to child by sneezing and coughing. It takes two to three weeks for the symptoms to appear after infection with the virus.

In New Zealand, about 90% of children get chickenpox and then, normally, they acquire immunity to it - the 10% who do not have childhood chickenpox become adolescents and adults who are still susceptible to being infected with the virus.

In people who have had chickenpox, the varicella virus can lie dormant for many years and then be reactivated much later in life - normally after the age of 40 - and when this occurs the illness is called shingles.

What are the symptoms?

Initially, the child (or adult) with chickenpox may have cold-like symptoms, mild headache, and a moderate fever. This is quickly followed by an itchy, red and pimply rash, which soon develops into clear-fluid filled, blister-like sores. The rash normally starts on the face and scalp, and later spreads to other parts of the body. Some children develop only a few of the sores and others have them all over their bodies - including in the vagina and mouth or up the nose.

What is the treatment?

For some children, the rash may be no more than a passing inconvenience, but for others, it can be very unpleasant. Treatment is, therefore, aimed at controlling the symptoms.

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. Cut their fingernails very short and make sure that their hands and fingernails are kept clean.

If the rash or sores are very itchy, bathe the child in a warm (but not too hot) bath with half a cup of baking soda in it. Your pharmacist or doctor will also be able to recommend some anti-itch preparations if your child is very distressed. Calamine lotion can be useful as well.

Paracetamol should be given to children as directed on the bottle or packaging to reduce the fever and ease any headaches. Aspirin should not be given to children as it is associated with the serious but rare Reye's syndrome.

Make sure your child drinks plenty of clear fluids (juice, 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.

As chickenpox is caused by a virus no antibiotics will be prescribed, however, they may be recommended by your doctor if your child develops a secondary bacterial skin infection as a result of having chickenpox.

Preventing infection

Chickenpox is most infectious from two days before the rash is present until after scabs have formed on the sores - this takes about seven days. Do not send your child to school or preschool during this time.

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.

Vaccination

Chickenpox (varicella) vaccination is not included in the childhood immunisation programme in New Zealand as the Ministry of Health does not recommend the routine use of this vaccine for normal, healthy children. However, the vaccine is available and licensed for use in New Zealand, but it is not subsidised, so the patient or parent must pay for it. The vaccine can be given to children over about one year of age and adults. Children aged under 13 years require one dose, whereas anyone over 13 years requires a second booster shot about six weeks later. The recommendations from the Ministry of Health for who might benefit from the vaccine are summarised below:

• individuals with suppressed immunity (eg, children with leukaemia or renal failure, under specialist supervision)
• where such immune-suppressed individuals cannot be vaccinated, family members and close contacts should be vaccinated to provide a 'ring fence' against varicella infection
• health care workers
• healthy infants and children whose parents wish them to avoid having chickenpox
• susceptible adolescents and adults, in view of their increased risk of serious outcomes from varicella infection relative to children.

The US Advisory Committee on Immunization Practices advises suceptible people in the following high risk groups have varicella vaccination:

• persons who live or work in environments where transmission of varicella is likely (eg, staff in early childhood services, residents and staff members in institutional settings)
• persons who live and work in environments where transmission can occur (eg, college students, inmates and staff members of correctional institutions, and military personnel)
• non-pregnant women of childbearing age
• adolescents and adults living in households with children
• international travellers.

The use of varicella vaccines overseas indicates that, in general, side effects include local reactions, fever and mild rash in normal, healthy individuals, are these are mild and self-limiting symptoms.

For further information and support talk with your doctor, practice nurse or pharmacist.

Written by Anna Mickell, RCpN, reviewed by everybody