- Chickenpox is usually easily recognised by a characteristic rash of small blisters.
- Chickenpox is usually a mild and short-lived illness in children.
- Adults are at greater risk of having 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.
- A vaccine for chickenpox is available for infants from the age of 9 months.
Chickenpox (varicella) occurs worldwide as a childhood disease, which lasts four to five days and presents with fever and a widespread rash of small blisters (vesicles), usually distributed on the chest, back, face and the arms and legs.
Sometimes the disease can be more severe, affecting internal organs such as the lungs and liver. An individual can only ever have one episode of chickenpox in their lifetime. Once that person has recovered, 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 remains hidden in some nerve cells, without causing any illness. This hidden or ‘’latent” virus may later on be reactivated by a variety of causes like stress, malnutrition and in the elderly. The reactivated virus will cause an illness called shingles. Shingles is a band of painful blisters, usually involving the skin on the side of the chest or abdomen, but may involve the face.
Chickenpox results when a person becomes infected with the varicella-zoster virus [ VZV]. Following the infection this virus spreads throughout the body, as shown by the appearance and distribution of the rash which may cover the entire body.
Like its relative the Herpes simplex virus, once the chicken pox illness is over, the varicella-zoster virus persists in a person for the rest of their life. The virus remains dormant in certain nerves, usually in the spinal nerves.
Chickenpox can occur in anyone who has not had the illness before. Shingles can only occur in someone who has previously been infected with chickenpox.
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 by contact or touch. 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 9 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") is the result of reactivation of the VZV virus in one of the spinal nerves; the virus travels down the nerve, producing large blisters localised in the area that the nerve supplies. Shingles therefore involves an area of skin which is "wired" by one sensory nerve (this area of skin is known as 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, due to the immune system’s "memory" of the virus reducing over time. The immune system may not be able to effectively control the latent virus. Anyone whose immune system is compromised also loses the ability to control this virus; for instance immune control can be reduced by stress, poor diet, immunesuppression due to chemotherapy treatment and in transplant patients or people with HIV infection.
Chickenpox symptoms begin with a moderate fever, headache and listlessness a day or two before the rash appears. In adults these preliminary symptoms may be more severe, with flu-like muscle pains. The rash initially appears as pinkish bumps of a few millimetres across, usually on the chest or abdomen. Within hours the bumps become itchy blisters, containing a clear fluid (vesicles). The vesiclesbreak down quite rapidly and form crusts (scabs), but a new crop of vesicles appears just as the previous crop starts to crust. Typically 250 to 500 vesicles will form during the chickenpox illness. The chickenpox rash is usually 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 blisters, blisters may also occur in the mouth and throat, on the eyelids and in the genital and anal areas. In these areas the blisters tend to break down, forming painful ulcers. Blisters in the mouth make eating or drinking difficult. The blisters usually stop forming by the fifth day of the rash, and most of these become crusted by sixth day of the illness.
While chickenpox is usually a mild illness in children, there are a number of possible complications which are fortunately fairly rare: Chickenpox encephalitis may occur in about 1 in 1,000 cases, usually towards the end of the disease. Chicken pox pneumonia is another possible complication, but is less common in children than in adults.
Chickenpox occurs everywhere in the world. It seems to spread more easily in the cooler months and there are usually more infections in winter and spring.
Most children (three out of four) get chickenpox by the age of 9 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 also get shingles in their lifetime. The risk of shingles increases steadily after the age of 50.
It usually takes about 14 days from the time people are exposed to the chickenpox virus to the time when symptoms start to occur. Sometimes this period can be as short as 10 days or as long as 21 days. The preliminary symptoms (fever, headache) usually begin 24 to 36 hours before the rash appears.
The fever subsides a few days after the rash appears and the rash usually lasts for 5 or 6 days. The last dried-up crusts fall off by 10 days.
Generally 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: Children and adults whose immune systems are compromised are at particular risk. Examples of conditions that compromise the immune system include various forms of cancer, leukaemia, lymphoma and HIV/AIDS. Some drugs, such as high doses of cortisone used for severe asthma, arthritis or kidney diseases may compromise the immune system. Immunocompromised people are prone to an extensive, severe rash, possible damage to internal organs (such as pneumonia or hepatitis), to haemorrhagic chickenpox and to a prolonged course of the illness. Chickenpox may even be fatal in immunocompromised people.
When to see a doctor
See your doctor if:
- A child or adult with chickenpox develops a very extensive chickenpox rash which is painful, and especially if bleeding occurs into the skin.
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.
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.
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.
- Loose cotton clothing
- Sometimes an antihistamine with sedating effects may be given to reduce itching.
To avoid dehydration
- If necessary, administer analgesics such as paracetamol to relieve pain or discomfort.
- Give cool drinks, preferably water, as frequently possible.
To prevent secondary skin infection
- Keep children’s fingernails clean and clipped short to minimise harm from scratching.
Never use aspirin or Ibuprofen! Paracetamol is safe to use.
If 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 chicken pox virus. In South Africa it is produced by the Natal blood transfusion service. It is scarce and is only available to those at great risk.
Fortunately the anti-viral drug Acylovir 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 intra-venously 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.
Previously chickenpox was essentially unavoidable. However, a vaccine against chickenpox is available. This is a safe and effective vaccine. It is in use as a routine childhood vaccination in some countries. It is available in South Africa, but is not yet a routine childhood state-funded vaccination..
The chicken pox vaccine (known as varicella vaccine) is 95% effective in preventing chicken pox infection. It 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 it.
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.
Following infection with chicken pox, a person is infectious from about two days before the rash until all the blisters have crusted, which usually takes about 6 days from the start of the rash. In order not to infect others, one should avoid social contact while the chicken pox blisters are present. School-going children should not attend school until all their blisters have crusted; staying home for six days is usually sufficient.
Previously reviewed by Dr Eftyhia Vardas BSc (Hons), MBBCh, DTM&H, DPH, FC Path (Virol), MMed (Virol)
Reviewed by Prof Eugene Weinberg, Paediatrician, February 2011