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 are the most common modes of transmission, particularly in children.
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 as shingles (herpes zoster). Shingles can occur at any age but is most common in adults over 60 years of age.
Signs and symptoms
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 to 21 days after exposure to the virus. Full recovery from chickenpox usually takes 7–10 days after the symptoms first appear.
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.
People with chickenpox should remain at home until they are no longer infectious. Supportive treatment includes:
- 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 ½ cup of sodium bicarbonate 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 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
- Antiviral medications (eg: acyclovir) may be prescribed for some people.
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 stream infection), and rarely encephalitis (swelling of the brain) and death.
Chickenpox can cause foetal abnormalities 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.
Immune-compromised people – 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.
Prevention / vaccination
The chickenpox (varicella) vaccine is the best way to prevent chickenpox.
A vaccine against the varicella virus is available for infants from nine months of age, children, and adults. 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 recommended and funded for certain high risk groups, and is available at a cost to other patients. From 1st July 2017, the varicella vaccine will be funded for all children as part of the New Zealand Ministry of Health’s childhood immunisation schedule.
Further information and support
Immunisation Advisory Centre (IMAC)
Freephone: 0800 IMMUNE (0800 466 863)
Freephone: 0800 933 922
Freephone: 0800 611 116
KidsHealth (2014). Chickenpox (Web Page). Auckland: Paediatric Society of New Zealand and Starship Foundation. www.kidshealth.org.nz/chickenpox [Accessed: 27/07/16]
Mayo Clinic (2016). Chickenpox (Web Page). Rochester: Mayo Foundation for Medical Education and Research. http://www.mayoclinic.org/diseases-conditions/chickenpox/home/ovc-20191271 [Accessed: 27/07/16]
Ministry of Health (2014). Varicella (chickenpox). Immunisation Handbook 2014 (2nd Edition). Wellington: Ministry of Health. http://www.health.govt.nz/publication/immunisation-handbook-2014-2nd-edn [Accessed: 28/07/16]
DermNet NZ (2016). Chickenpox (varicella) [Web Page]. Hamilton: DermNet New Zealand Trust. www.dermnet.org.nz/viral/varicella.html [Accessed: 27/07/16]