Chickenpox

Chickenpox is a highly infectious disease that in past years has infected around 90% of New Zealand children. Symptoms include fatigue, mild fever and loss of appetite, followed by a red rash and itchy blisters. Treatment will focus on reducing fever and itching.

Chickenpox vaccination is fully funded for New Zealand children and is reducing the proportion of New Zealanders who contract the disease.

General information

Chickenpox (varicella) is usually a mild, self-limiting disease in healthy children. However, it can be severe if contracted by babies, or children and adults with immune systems that aren't functioning properly.

Chickenpox is caused by infection with the varicella zoster virus, a member of the herpes family of viruses.

The virus is spread in droplets of saliva through the air or by direct contact with the fluid from the blisters of the infected person. Coughing and sneezing is the usual way the disease is transmitted.

The disease most commonly affects the five to nine-year-old age group but with increased use of early childhood centres, a greater proportion of infections may now be occurring in pre-school-aged children. Chickenpox is most common during winter/spring.

One bout of chickenpox gives lifelong immunity from contracting the disease again. However, the virus remains in the body for life and can be reactivated years later as shingles (herpes zoster). Shingles can occur at any age but is most common in adults over 60 years of age.

Signs and symptoms

Initial symptoms of chickenpox include fatigue, a mild fever, lack of appetite, and a feeling of being generally unwell. This is quickly followed (usually within 24 hours) by the development of a red rash, which usually appears on the chest and/or back first, later spreading to the face, scalp, arms, and legs.

Twelve to 48 hours later the rash develops into small red spots. These then turn into yellow fluid-filled blisters, which burst and dry up 3-4 days after they appear. There may be several crops of spots occurring over 4-5 days. The spots cause itching, which may be severe. They may occur all over the body, including the mouth and genital area. Some people may have only a few spots whereas others will have hundreds.

Symptoms start appearing 10-21 days after exposure to the virus. Full recovery from chickenpox usually takes 7-10 days after the symptoms first appear.

Diagnosis

Diagnosis of chickenpox is usually based on symptoms, in particular the presence of its characteristic itchy red rash and different types of lesions being present at the same time. For a diagnosis of chickenpox see a doctor or practice nurse. Laboratory tests on blood and skin lesion samples can confirm chickenpox.

Consult a doctor immediately if the person seems very sick, confused or difficult to waken, or if they have trouble walking or have a stiff neck. Also consult a doctor if the blisters become infected or if there are spots in the eyes, ears or mouth.

Treatment

Chickenpox in otherwise healthy children does not normally require medical treatment - the infection is usually allowed to run its course.

High-risk individuals, including people with weakened immune systems and pregnant women who are not already immune to the varicella virus, may be given antiviral drugs such as acyclovir or varicella-zoster immunoglobulin (ZIG), which is a human blood product, to reduce the severity of chickenpox and risk of complications. However, to be beneficial, antiviral drugs and ZIG must be given very soon after exposure to the varicella virus.

People with chickenpox should remain at home until they are no longer infectious. Supportive treatment includes:

• Rest
• Pain relief such as paracetamol to relieve fever. Aspirin should not be given, as this has been associated with Reye’s disease (a rare disorder affecting the liver and brain) in children with chickenpox
• Itching can be treated with lotions such as calamine available from a pharmacy.
• Tepid baths with sodium bicarbonate, uncooked oatmeal or colloidal oatmeal, or solutions such as Pinetarsol added can also be helpful in relieving itching
• Because the mouth and throat can be affected, offer soft food and cool drinks. Avoid salty foods and citrus fruits
• To prevent infection of the sores, trim children’s fingernails short or put gloves on their hands, and wash hands frequently with antibacterial soap. Discourage scratching as much as possible
• Dress children in light, loose fitting clothing or pyjamas. Overheating and friction from clothing can worsen itching
• Antihistamines such as diphenhydramine to help relieve itching.

Complications

Although chickenpox is usually a mild and self-limiting disease, complications potentially requiring hospitalisation or leading to death can occur.

Bacterial infection of the skin, which may need to be treated with an antibiotic, is the most common complication of chickenpox. Serious complications include pneumonia, septicaemia (blood infection), and rarely encephalitis (swelling of the brain) and death.

Chickenpox can cause foetal abnormalities and low infant birth weight if a non-immune woman contracts the disease between weeks 8 and 20 of pregnancy. Additionally, there is a risk of serious disease in the new-born baby if the mother contracts chickenpox between the fifth day before delivery and the second day after the baby is born.

Children with chickenpox should therefore be kept away from pregnant women and new-born babies until they are no longer infectious. Pregnant women who have not had chickenpox should see their doctor for control measures if they are exposed to the disease.

People with weakened or compromised immune systems – for example those who are HIV positive, organ-transplant recipients, and children with leukaemia – are also susceptible to serious illness as a result of varicella virus infection.

Vaccination and prevention

A person with chickenpox is infectious from 1-2 days before the rash first appears until after the final crop of blisters have formed scabs, approximately 5-10 days later. The nature of the infectious period makes it very difficult to prevent the disease from spreading. Nonetheless, children should stay away from day care or school, and public places, while they are infectious. Adults with chickenpox who work with children should also stay home.

The chickenpox (varicella) vaccine is the best way to prevent chickenpox.

One dose of the vaccine provides approximately 99% protection against severe chickenpox and 80% protection against chickenpox of any severity. Vaccination may prevent or reduce the severity of chickenpox if it is given within 3–5 days of exposure to someone with the disease.

The varicella vaccine is available from GPs. It is fully funded for infants at 15 months of age or children at 11 years of age not previously infected with or vaccinated against chickenpox, as part of the New Zealand Ministry of Health’s national immunisation schedule. The varicella vaccine is also recommended and funded for certain high-risk groups and is available at a cost to other patients.

Further information and support

For more information on chickenpox vaccination, please see your GP or practice nurse, or contact:

Immunisation Advisory Centre (IMAC)

Freephone: 0800 IMMUNE (0800 466 863)
Website: www.immune.org.nz
For more information about chickenpox, see your GP or practice nurse, or contact:

Plunketline

Freephone: 0800 933 922
Website: www.plunket.org.nz

Healthline

Freephone: 0800 611 116
Website: www.healthline.govt.nz

References

KidsHealth (2017). Chickenpox (Web Page). Auckland: Paediatric Society of New Zealand and Starship Foundation. https://www.kidshealth.org.nz/chickenpox [Accessed: 25/03/18]
Mayo Clinic (2019). Chickenpox (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/chickenpox/symptoms-causes/syc-20351282 [Accessed: 25/03/19]
Ministry of Health (2017). Varicella (chickenpox). Immunisation Handbook 2017 (2nd edition, March 2018). Wellington: New Zealand Ministry of Health. https://www.health.govt.nz/publication/immunisation-handbook-2017 [Accessed: 25/03/19]
DermNet NZ (2016). Chickenpox (varicella) [Web Page]. Hamilton: DermNet New Zealand Trust. https://www.dermnetnz.org/topics/chickenpox/ [Accessed: 25/03/19]

Reviewed - March 2019

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