Conditions

Chickenpox (varicella) occurs worldwide as a childhood disease, which lasts four to five days and has the features of fever and a widespread rash of small blisters (vesicles).

  • Chickenpox is usually easily recognised by its characteristic rash of small blisters.
  • Chickenpox is usually a mild and short-lived illness in children
  • Adults are at greater risk of severe chickenpox.
  • Chickenpox in pregnancy poses certain risks.
  • Shingles is a long-term consequence of chickenpox.
  • There is an antiviral drug that can be used to decrease the severity and duration of a chickenpox attack in certain severe cases and under special circumstances like in immune suppressed individuals.
  • A vaccine for chickenpox is now commercially available.

Description

Chickenpox (varicella) occurs worldwide as a childhood disease, which lasts four to five days and has the features of fever and a widespread rash of small blisters (vesicles) usually distributed on the chest, back and face with few blisters evident on the arms and legs.

Sometimes the disease can be more severe, with internal organs affected, such as the lungs and liver. An individual can only ever have one episode of chickenpox in their lifetime. Once that person has recovered from chickenpox they have life-long immunity to chickenpox. However, the virus that causes chickenpox belongs to the herpes virus family and like other members of this family, after recovery from the initial infection, the virus never actually leaves the host but 'hides out' in a latent state not causing any illness in certain nerve cells. This 'latent' virus does not cause any illness until it is 'reactivated' by a variety of different factors like stress, malnutrition and old age. The reactivated virus will cause illness but in another form different to the first infection. In the case of chickenpox the reactivation of the virus many years after a chickenpox attack causes shingles. Shingles is a band of painful blisters confined to one area of skin.

Cause

Chickenpox is the illness that occurs when a person is first infected with the varicella-zoster virus, VZV, also known as human herpes virus type III. During the first (primary) infection the virus is able to spread throughout the body – evident from the distribution of the rash over the whole body.

Like its relative the Herpes simplex virus, the varicella-zoster virus persists in a person for the rest of their life. The virus becomes dormant in nerve centres in the spine.

Chickenpox can occur in anyone who has not had the illness before. Shingles can only occur in someone who has had chickenpox before.

The varicella-zoster virus is present in throat secretions of a person just before or just after they develop the chickenpox rash. These secretions can reach another person as airborne droplets. The skin blisters of chickenpox and shingles also contain infectious viruses, which can reach the nose or mouth of another person, for example via fingers. Face-to-face exposure to someone with early chickenpox will put you at risk of infection. Even spending some time in the same room as a person with early chickenpox will put you at risk.

The highest risk is associated with living in the same household as a person with chickenpox, and nine out of 10 people who have not had chickenpox before will contract the disease under these circumstances.

Shingles (a condition also known as “herpes zoster” or “zoster”) is the result of reactivation of the VZV virus within one of these spinal nerve centres; the virus travels down a nerve and its branches into the skin, where it multiplies and produces blisters localised in the area that the nerve usually supplies. Shingles therefore involves an area of skin which is “wired” by one sensory nerve (the area of skin is also called a dermatome). The dermatomes that are commonly affected during a shingles attack are those on the chest, abdomen or face. Only one dermatome is affected in a particular individual at one time.

While shingles can occur at any age, it usually occurs in the elderly, probably because the immune system's “memory” of the virus lessens over time and the immune system can therefore no longer effectively control the latent virus. Anyone whose immune system is compromised also loses the ability to control the virus, for instance immune control can be caused by stress, poor diet, immunesuppression caused by drugs and in transplant patients or HIV infection.

Symptoms

A mild headache, moderate fever and unwell feeling usually starts a day or so before the rash appears. In adults these preliminary symptoms can be more severe, with flu-like muscle pains. The rash initially appears as pinkish bumps of a few millimetres across, usually somewhere on the trunk.

Within hours the bumps become itchy blisters containing a clear fluid (vesicles). The vesicles quite rapidly break down and crust (scab), but a new crop of vesicles appears just as the previous crop starts to crust. Typically 250 to 500 vesicles will form.

In chickenpox the rash is most dense on the trunk (chest and abdomen), with fewer vesicles on the face and limbs.

Vesicles on the scalp may be accompanied by swollen lymph glands at the back of the neck. Along with the skin vesicles, vesicles occur in the mouth and throat, under the eyelids and in the genital and anal openings. On these wet surfaces the vesicles tend to break down into ulcers and can be quite painful.

One consequence of this is that swallowing may be difficult. Vesicles usually stop appearing by the fifth day of the rash, and most vesicles will be crusted by the sixth day.

While chickenpox is usually a mild illness in children, there are a number of possible complications:

  • Because the rash is very itchy and children cannot help scratching, the commonest complication is infection of vesicles by bacteria; this is known as secondary infection. With secondary infection the skin will redden and the vesicle sites will produce pus. In more severe cases the infection penetrates the tissues under the infected skin, causing swelling. While the chickenpox rash does not cause skin scarring, secondary skin infection can leave scars. A rising temperature can be a warning sign of serious secondary bacterial infection that has entered the bloodstream.
  • A different type of serious complication (haemorrhagic chickenpox) reveals itself by bleeding into the vesicle sites.
  • Chickenpox pneumonia is a serious complication that occurs when vesicles form in the lungs, and becomes evident by shortness of breath and a cough.
  • Chickenpox encephalitis complicates about 1 in 1,000 cases of chickenpox. It tends to occur toward the end of the illness. A common way in which children are affected is by loss of sense of balance so that they develop a staggering walk. This is often associated with involuntary movements of the eyes. Other signs of encephalitis are personality change, irritability or drowsiness, which in severe cases will progress to loss of consciousness.

Prevalence

Chickenpox occurs everywhere in the world. It is slightly less prevalent in the tropics and more people in these regions reach adulthood without having had chickenpox. In other parts of the world it seems to spread more easily in the cooler months and there are more infections in winter and spring.

Most children (three out of four) get chickenpox by the age of nine or 10 years and most people will have had chickenpox by the time they reach adulthood. About one in seven people who have had chickenpox will experience shingles in their lifetime. The risk of shingles increases steadily after the age of 50 years.

Course

It usually takes about 14 days from the time people are exposed to varicella-zoster virus to when they develop symptoms, but this period can be as short as 10 days or as long as 21 days. The preliminary symptoms (fever, headache) can start 24 to 36 hours before the rash.

The fever should subside a few days into the rash, and the rash itself usually lasts less than one week (the last crusts falling off by 10 days).

Risk factors

In general, children are least likely to have complications from chickenpox. Babies under one year old are more vulnerable, and from puberty onwards teenagers and adults are more prone to severe chickenpox and its complications.

Certain groups of people are particularly at risk for severe chickenpox:

  • A baby born to a mother who herself develops chickenpox in the period from five days before to two days after delivery is very vulnerable. This is because no protective immunity will have formed in the mother and been passed to the baby before it becomes infected. Special and urgent treatment is indicated for newborn babies exposed to chickenpox by their mothers.
  • Chickenpox in the first 20 weeks of pregnancy can very occasionally (one to two percent of cases) cause damage to the developing foetus. The types of abnormalities that can occur affect the skin (scarring), the limbs (shortening), the brain (mental retardation) and the eyes (blindness).
  • In addition, chickenpox at any stage of pregnancy is a significant risk to the mother, particularly for chickenpox pneumonia.
  • Children and adults whose immune systems are compromised are at particular risk from chickenpox. Examples of conditions that compromise the immune system are leukaemia, lymphoma and HIV/AIDS. Some drugs, such as high doses of prednisone for severe asthma, arthritis or kidney diseases, compromise the immune system. Immunocompromised people are prone to a dense rash, damage to internal organs (such as pneumonia or hepatitis), to haemorrhagic chickenpox and to a prolonged course of the illness. Chickenpox is not infrequently fatal in immunocompromised people.

When to see a doctor

See your doctor if:

  • You or your child are immunocompromised and have been exposed to someone with chickenpox, or show signs of chickenpox
  • Your newborn or baby younger than one year has been exposed to someone with chickenpox, or shows signs of chickenpox, especially if the mother is the source of infection
  • You are pregnant and have been exposed to someone with chickenpox (especially if you know that you have not had chickenpox) or you show signs of chickenpox
  • You are an adult and develop signs of chickenpox
  • A child or adult with chickenpox develops shortness of breath, cough, drowsiness or confusion, blood in the urine or any other unexpected complaint
  • A child or adult with chickenpox develops skin problems such as a spreading redness or pus or swelling or bleeding into the skin.

Visit preparation

If you or your child has chickenpox, advise your doctor's receptionist when making an appointment so that precautions can be taken to avoid exposing other patients who are at risk.

Diagnosis

Chickenpox is usually an easily recognisable disease because of the distinctive rash of blisters. For this reason laboratory tests are not often necessary. If there is doubt, the virology laboratory can do rapid tests on fluid obtained from a vesicle with a tiny needle and syringe or on cellular material obtained by swabbing the raw base of a vesicle.

In situations of exposure to chickenpox, the knowledge that a person has definitely had chickenpox before is very useful when deciding what measures, if any, need to be taken. Often this information is not known or is incorrect (for example, when adults try to recall whether they had chickenpox as a child). In circumstances where an at-risk person has been exposed to chickenpox, a blood test can be done to show whether they have antibodies to the varicella-zoster virus. The presence of antibodies would mean that they had had chickenpox in the past and that they are therefore wholly or partially (in the case of immunocompromised people) protected against chickenpox.

Treatment

Home

Do not use aspirin- or ibuprofen-containing drugs for persons with chickenpox. Aspirin use is associated with a rare but fatal form of encephalitis (Reye's syndrome) in children with chickenpox. Ibuprofen use has recently been associated with a very dangerous form of creeping tissue infection in persons with chickenpox.

Mild cases of chickenpox in children can be managed with simple measures to control the symptoms.

For itching

  • Luke-warm baths
  • Cold compresses
  • Calamine lotion
  • Loose cotton clothing

To avoid dehydration

  • Encourage children to have regular drinks.
  • If necessary, administer analgesics to relieve pain on swallowing.

To prevent secondary skin infection

  • Frequently bath with soap and water and pat the skin dry with a soft towel; then put on clean underclothing.
  • Keep children's fingernails clean and clipped short to minimise harm from scratching.

For moderate fever and discomfort

Non-aspirin based anti-pyretics (fever-reducing drugs) and analgesics (painkillers) such as paracetamol or mefenamic acid can be given according to the recommended dose. (Do not use aspirin- or ibuprofen.)

Medication

For more severe itching – for example, if it prevents sleep – your doctor or pharmacist may recommend anti-histamine drugs, some of which also have useful sedative effects.

Any significant skin infections should be treated with antibiotics by mouth (antiseptic creams are not adequately effective).

When a person who is at very high risk has been exposed to chickenpox, (such as children with leukaemia, newborns of mothers with chickenpox) an immunoglobulin preparation (Varicella Zoster immune globulin or VZIG) can be given to them by intramuscular injection to provide “instant immunity”. While VZIG may not prevent chickenpox, unless given very early after exposure to an infected individual, it does reduce the severity.

VZIG is prepared from blood donations from people with very high blood antibody levels to the varicella-zoster virus. In South Africa it is produced by the Natal blood transfusion service. It is very scarce and so is only available to those at the very highest risk.

Fortunately the anti-viral drug acyclovir is effective and safe for the treatment of chickenpox. (It is the same drug that is effective against Herpes simplex infections.) Any patient who is at risk of severe chickenpox should be treated with acyclovir at the earliest sign of the disease. It can be used safely even in the youngest babies. It can be given orally but may be administered intravenously in dire situations (such as chickenpox pneumonia).

Because of the significantly increased risk of complications from chickenpox in adults even if they are healthy, some experts now recommend that all people older than 18 years be treated with acyclovir, preferably within 24 hours of the start of the illness.

Acyclovir and new drugs derived from it can also be of some benefit in reducing the symptoms in shingles.

Although in principle one should avoid most drugs in pregnancy, no adverse effects for the foetus have been reported in the many women who have been treated with acyclovir. Therefore the very significant risk to the pregnant mother should be the predominant consideration in deciding whether to treat chickenpox in pregnancy.

Unfortunately there is no proof yet that treatment with acyclovir will protect the developing foetus from damage that can result from infection in the first half of pregnancy.

Counselling will not usually recommend terminating a pregnancy on account of maternal chickenpox since the risk to the foetus is small and unpredictable. However the decision will depend on individual circumstances. Monitoring the foetus by ultrasound may detect an abnormality but cannot be relied upon to exclude all abnormalities.

Prevention

Up till now, infection with chickenpox has been essentially unavoidable. However, a vaccine against chickenpox has been developed recently and has been used successfully, specifically to protect persons who are at risk. It is already in use as a routine childhood vaccination in some countries, for example the USA. It has recently been licensed in South Africa but is unlikely to become a routine, state-funded childhood vaccination while there are more urgent health priorities.

The varicella vaccine is a live attenuated or weakened vaccine derived from a strain of the virus known as the 'Oka' strain. This vaccine is almost 95% effective to prevent varicella infection if two doses are given at least four weeks apart and can be safely used in infants from nine months of age. Ask your doctor about the chickenpox vaccine if your child has not yet had chickenpox.

Great care should still be taken to avoid exposing immunocompromised people (for example, during hospital visits from friends) to anyone with chickenpox and even to anyone who has recently been in contact with chickenpox (who could be in the very early stages of infection) or has recently received the varicella vaccine because the vaccine virus strain can also be transmitted between individuals.

In a natural infection, a person is infectious from about two days before the rash until all the blisters have crusted, which usually takes five to six days from the start of the rash. In order not to infect others, one should avoid social contact while moist blisters are present. School-going children should not attend school until all their blisters have crusted; staying home for six days is usually sufficient.

Further publications on the topic