Chickenpox

Introduction

Chickenpox is caused by a virus called the varicella-zoster virus (varicella is the medical name for chickenpox).

Chickenpox is a mild but highly infectious disease that most children catch at some point. It is most common to catch the disease between March and May. It takes 10-21 days for the symptoms to show after you have come into contact with the virus. This is called the 'incubation period'.

Chickenpox is most common in children who are between two and eight years of age, although you can develop chickenpox at any age. You are infectious from about two days before the rash appears until roughly five days after. Therefore you or your child should stay at home until all of the blisters have fully crusted over, and this usually happens five to seven days after the first blister appears. After the last blister has burst and crusted over, you are no longer infectious.

Chickenpox spreads via tiny droplets of saliva and nasal mucus in sneezes and coughs from an infected person. The virus is already in these droplets, which is why it spreads so fast.

Once you have had chickenpox, you will very rarely catch chickenpox for a second time. This is because your body develops immunity to the chickenpox virus, which stops you from becoming re-infected.

Shingles

After a chickenpox infection, the virus stays in the body's nerve tissues (remains dormant). It does not do any harm because it is kept under control by the immune system, the part of the body that fights infection. At any time later in life, but usually when you are an adult, the virus can be reactivated (come back), causing a different form of the virus, known as shingles.

The first sign of shingles is usually a pain in the area of the affected nerve. Seven days later a rash will usually appear, followed by blisters, that tend to only affect one side of your body. If you have shingles you are contagious to anyone who has not had chickenpox. However, it is not possible to catch shingles from someone who has chickenpox.

Pregnancy

More than 90% of pregnant women are immune to the chickenpox virus (as a result of having it earlier on in life), so most women need not worry about developing the disease. Even if you develop shingles during pregnancy, it should not affect your baby in any way.

Chickenpox occurs in approximately three in every 1,000 pregnancies and can cause serious complications for both you and your child. Your GP will be able to advise you on any necessary tests or treatment you may require (see diagnosis and complications sections for further information).

Symptoms of chickenpox

The most commonly recognised symptom of chickenpox is a red rash, which covers the body. However, before developing a rash, you or your child may experience some mild flu-like symptoms. These symptoms may include:

• nausea,
• fever,
• aching, painful muscles,
• headache,
• generally feeling unwell, and
• loss of appetite.

These flu-like symptoms (especially fever) tend to be worse in adults than in children.

Rash

Shortly after these initial symptoms, a rash starts to develop. The rash normally appears in crops, and can usually be found:

• behind the ears,
• on the face,
• over the scalp,
• under the arms,
• on the chest and stomach, and
• on the arms and legs.

The rash starts as small, itchy, red spots. After approximately 12-14 hours, these spots develop into fluid-filled blisters, which are intensely itchy. These blisters can also form on the palms of your hands and the soles of your feet. After one to four days, these blisters will dry out and begin to crust over. After one to two weeks, the crusting skin will fall off naturally.

When to contact your GP

It is very important, if you are pregnant, or have a weakened immune system, that you contact your GP straight away if you have been in contact with someone who has chickenpox, regardless of whether you have any symptoms. You should also contact your GP if your baby has been in contact with the chickenpox virus and is less than four weeks old. Chickenpox in these people can cause serious complications if left untreated. It is therefore essential that you seek medical advice so that any necessary precautions or treatment can be provided.

You should also contact your GP straight away if you, or you child develops any abnormal symptoms. For example, if the blisters on the skin become infected, or if you, or your child start to experience pain in the chest, or difficulty breathing.

Diagnosing chickenpox

Tests are not normally needed to diagnose chickenpox, because an initial mild fever followed by a rash, blisters and scabs are very characteristic.

Chickenpox is usually easy to distinguish from other rashes. Occasionally it can be confused with other conditions which affect the skin, such as insect bites or scabies. If there is any uncertainty as to what is causing your or your child's symptoms, a simple blood test can be carried out to identify the virus.

Testing

If you are pregnant, breastfeeding or have a weakened immune system you are more at risk of developing complications. Babies less than four weeks of age are also at risk. If you fall into one of these groups and have been in contact with someone with chickenpox, or you suspect you, or your child may have developed the condition, then you should visit your GP straight away. You may require some tests to establish your immunity to the condition.

If you have had chickenpox in the past, then it is extremely unlikely that you will contract chickenpox for a second time. If you know you have never had chickenpox, or you are unsure whether you have, then you may need a blood test to check to see whether you are producing the antibodies which protect the body from the chickenpox virus. If your blood test result shows that you do have the antibodies, then you will naturally be protected from the virus. If you do not have the antibodies, then you will require close monitoring, in case symptoms develop.

Treating chickenpox

There is no cure for chickenpox, and the virus usually clears up by itself, even without any treatment. However, there are some things you can do to help ease the symptoms.

Painkillers

If you or your child is in pain, or has a fever, then you can give them a mild painkiller, such as paracetamol or ibuprofen.

Liquid, sugar-free paracetamol should be given to children under the age of 12. Short term use of either paracetamol or ibuprofen will not usually cause any side effects. Paracetamol can be used at any stage during pregnancy and breastfeeding, but ibuprofen should not be used after 30 weeks of pregnancy.

Ibuprofen is also unsuitable if you have asthma, or a history of stomach problems, such as stomach ulcers. If you are unsure as to whether ibuprofen will be suitable for you or your child, check with your GP, nurse or pharmacist. If your child is younger than three months old, always speak to your GP before you provide your child with any kind of pain relief.

Aspirin

If you suspect that your child has chickenpox, or if they have been diagnosed with the condition, it is very important that you do not give them aspirin. Children under 16 years of age should never be given aspirin, but is particularly important that your child does not take aspirin if they have a viral infection like chickenpox.

Medical studies have shown that there is a link between treating children who have chickenpox with aspirin, and the potentially fatal condition, known as Reye's syndrome. This condition almost always affects children and teenagers, and can cause severe brain and liver damage, as well as affecting other parts of the body. If Reye's syndrome is not diagnosed quickly, it can lead to disability and, in some cases, death.

Speak to your GP, or pharmacist, if you are unsure about which medicines you should give your child.

Fluids

Try to drink plenty of water to avoid dehydration. Sugar-free ice-lollies help to lower temperature and give children fluids, as well as soothing a sore mouth if it has become infected. They may be used in children over the age of four. Avoid food that may make your mouth sore (such as salty foods) and try having soups as they are easy to swallow (just make sure the soup is not too hot).

Fingernails

Keep children's fingernails clean and short to stop deep scratching. You may also consider putting socks over your child's hands at night to stop them scratching the rash as they sleep. This will also prevent any future scarring from the itching of scabs.

Clothing

If your child has a fever, or if their skin is sore and aggravated, then dress them appropriately to avoid overheating, or shivering. If you or your child has chickenpox, it is best to wear loose-fitting, smooth, cotton fabrics. This will help stop the skin from becoming sore and irritated.

Calamine lotion

If your child's skin is very itchy or sore, you could try using calamine lotion. This lotion is very safe to use, and will have a soothing, cooling effect on the skin.

Tepid sponging

If your child has chickenpox, avoid tepid (lukewarm) sponging.

Aciclovir

If you develop chickenpox whilst you are pregnant you may have to take an antiviral medicine, known as aciclovir. This ideally needs to be started within 24 hours of your rash appearing. It does not cure chickenpox, but does make the symptoms less severe.

If you are taking aciclovir, you should make sure you drink plenty of fluids.

You will normally have to take this medicine five times a day (at four hourly intervals) for seven days. This medicine may also be prescribed to newborn babies and, people with a weakened immune system who develop chickenpox, as they too are more at risk of developing complications.

Complications of chickenpox

Complications of chickenpox are rare in children. In children under five, the most common complication is when the rash of blisters becomes infected with bacteria. If your child's blisters become infected, they may require a course of antibiotics.

The people most at risk of developing complications are:

• adults,
• pregnant women,
• babies less than four weeks old, and
• people with a suppressed immune system (the system which fights and protects the body from infection).

Adults

Chickenpox can be more serious in adults than in children, and adults with the virus are more likely to be admitted into hospital. Approximately 5-14% of adults with chickenpox develop lung problems, such as pneumonia (inflammation of the lung tissue). If you smoke, the risk of you developing lung problems is much greater. Although more serious in adults, a vast majority of people make a full recovery from the chickenpox virus.

Pregnant women

If you are pregnant, chickenpox can occasionally cause complications for both you and your baby. The risk of you developing pneumonia is slightly higher if you are pregnant. Up to one in 10 women with chickenpox develop this condition. The further you are into your pregnancy, the more serious pneumonia tends to be.

If you get chickenpox while you are pregnant, the risk to the developing foetus is small, and it will often have no effect on the baby whatsoever. However, your child may develop shingles during the first few years of life if the varicella infection that occurred while he or she was in the womb is reactivated.

Chickenpox can affect your baby in different ways, depending on what stage of the pregnancy you are in. The effects of these stages are outlined below.

The first 20 weeks

If your baby is infected with chickenpox in the first 20 weeks of your pregnancy, there is a risk that your child could develop a condition known as fetal varicella syndrome. However, this syndrome is rare, and the risk of it occurring in the first 12 weeks of pregnancy is less than 1%. Between 13 and 20 weeks, the risk is 2%. Although rare, this syndrome can cause serious complications including:

• scarring of the skin,
• eye defects, such as cataracts, which causes the lens in the eye to cloud over,
• shortened limbs, and
• brain damage.

After 37 weeks

If you contract chickenpox after 37 weeks, your child is at risk of being born with chickenpox. The risk of your baby being born prematurely is also slightly increased.

If you develop chickenpox seven days before, or seven days after giving birth, your newborn baby may develop a more serious type of chickenpox. In a few, severe cases, this form of chickenpox can be fatal.

You are at greater risk of complications if you catch chickenpox when you are pregnant if:

• you smoke, or
• you have a lung disease such as bronchitis or emphysema, or
• you are taking steroids or have done so in the last three months.

See your GP urgently if you are pregnant and think you may have chicken pox. The same advice applies if you think you have chicken pox within seven days of giving birth. This is so that any necessary precautions can be made to prevent you or your baby developing any further complications.

Immune system

The immune system is the body's way of defending itself against disease, bacteria and viruses. If your immune system is weak or does not function normally, it means that you are more susceptible to developing viruses such as chickenpox, because your body produces fewer antibodies to fight off the infection.

You may have a weakened immune system if you:

• are undergoing chemotherapy,
• have HIV or AIDS, or
• take immunosuppressive drugs to protect your organ or bone marrow transplants.

If you have a weakened immune system, you are also more at risk of developing complications from chickenpox. These complications include pneumonia, septicaemia (blood poisoning), and meningitis.

Preventing chickenpox

Should I keep my child home from school or nursery?

If your child has chickenpox, you should inform your child's school or nursery of the situation. The Health Protection Agency recommends that children can return to school or nursery once the blisters have fully crusted over, and this usually happens 5-7 days after the first blister appears. After the last blister has burst and crusted over, children are no longer considered infectious. However, they are still infectious up until this time.

If you, or your child has recently been exposed to the chickenpox virus, you may not be able to visit friends or relatives in hospital - you should telephone the ward to check first. It is also best that you, or your child avoids contact with pregnant women, newborn babies, and anyone who has a weak immune system (such as people having chemotherapy or those with HIV or AIDS).

Can my child travel on a plane if they have chickenpox?

If your child has chickenpox, they may not be allowed to fly until six days after the last spot has appeared).

Your child should be safe to fly once they are past the infectious stage and the blisters have crusted over, but it is best to check your airline policy first. You should inform the airline as soon as you have sought medical advice and had the illness diagnosed. It is also important to let your insurer know, to make sure that you will be covered if you have to delay or cancel your holiday, or if you need to extend your stay until your child is well enough to fly home.

How can I stop the virus spreading?

The chickenpox virus can sometimes be spread through contact with inanimate objects, or items that have been infected with the virus, such as children's toys, bedding, or clothing. In order to help stop the virus spreading, you can wipe any objects, or surfaces with a sterilising solution, such as Milton, and make sure that any infected clothes, or bedding, are clean and regularly washed.

References

• Hall S, Maupin T, et al. Second varicella infections: Are they more common than previously thought? Pediatrics. 2002;109:1068-1073