Chickenpox is an acute and highly contagious viral infection caused by the varicella-zoster virus. It is sometimes called varicella.
How it is spread
The virus may be transmitted by direct person to person contact, via droplet or airborne spread of respiratory secretions, or by contact with articles infected with the respiratory secretions or blister fluid of an infected person.
What are the symptoms
The first symptoms generally develop between 2 to 3 weeks, with the average being 14 to 16 days, after the person is exposed. Chickenpox begins with fever, fatigue and loss of appetite followed by a generalised rash a day or so later.
The rash is more concentrated over the trunk, face and scalp and starts as itchy red spots but rapidly progresses to blisters. The blisters last 3 to 4 days before turning into scabs and drying out.
Several crops of blisters will appear over a period of days, resulting in various stages of development present on the body at any one time. Healthy adults and children generally recover within 10 days.
How serious is chickenpox
Chickenpox is usually a disease of childhood, with most cases occurring in the under 15 year age group. In children it is usually a mild illness of short duration with complete recovery. Since 2005 Australian children have been vaccinated for chickenpox at 18 months of age.
This growing cohort of immune people is markedly decreasing the disease occurring in this age group.
A common side effect of chickenpox is a secondary bacterial skin infection due to scratching of the itchy rash.
Although historically known as a childhood disease, adults, adolescents and people with weakened immune systems are at risk of developing more serious disease and the potentially life-threatening complications such as pneumonia or encephalitis (inflammation of the brain).
Pregnant women and newborn babies are at risk of severe side effects if they are exposed to chickenpox.
All women who develop chickenpox in their pregnancy or in the first few days after the delivery of their baby should seek urgent medical advice.
Previously uninfected pregnant women who have been in contact with a person with chickenpox should see their doctor as soon as possible to discuss options for protection.
What is the infectious period
A person is infectious from 2 days prior to onset of the rash until the blisters have all crusted into scabs, usually about 5 days after they appear.
What is the treatment
Most people do not require medical intervention. Rest and fluids are encouraged.
Reducing the risk of skin infection by scratching can be aided/helped by the use of over the counter anti-itch soaps and lotions and by keeping fingernails short.
Paracetamol can be used to reduce fever. Aspirin must not be given to young children and adolescents due to the risk of developing Reyes Syndrome, a severe condition associated with aspirin use for viral infections.
Specific antiviral medication is available for chickenpox however it is reserved for those with severe disease or at risk for severe disease. A doctor’s prescription is required.
How chickenpox can be prevented
Chickenpox vaccine has been available free in Australia for children at 18 months of age and 13 years (given in Year 8 at school) since 2005. One dose of chickenpox vaccine given to children in these age groups will prevent disease in up to 85% of cases.
Since the vaccine program started preliminary data indicates that there has been a decrease in the number of children aged 1 to 4 years hospitalised with chickenpox.
Children who are not eligible for free vaccine as part of this program can purchase the vaccine privately with a doctor’s prescription. Vaccination is also recommended for some groups of people who may not have previously had chickenpox.
They include health care workers, teachers, child-care workers household contacts of immunosuppressed persons; and women prior to pregnancy.
If the person receiving the vaccine is over 14 years of age, 2 doses of vaccine are required.
For those uncertain about past immunisation or past disease it should be noted that it is safe to immunise people who may have previously had chickenpox disease or vaccination.
The vaccine is contra-indicated in pregnant women and immunosuppressed people.
People not immune to chickenpox and exposed to the disease can be administered chickenpox vaccine, preferably within 3 days, and up to 5 days after exposure to chickenpox to prevent or modify the severity of disease.
Those at high risk of complications from infection with varicellazoster virus eg. people with leukaemia, young babies or pregnant women should seek medical advice if they have been exposed to a case of chickenpox or shingles.
Administering zoster immunoglobulin (ZIG) to this group is effective in preventing or reducing the severity of chickenpox if given within 96 hours of exposure to the infection.
How can it be controlled
People with chickenpox should not attend child care, preschool, school or work until fully recovered or for at least 5 days after the rash first appears or longer if blisters are still present.
Note: once all remaining blisters have become scabs exclusion is no longer required. Encourage coughing or sneezing into the inner elbow rather than the hand and if tissues are used put them in the bin straight away.
Hands should be thoroughly washed after handling tissues, contact with an infected person or after blowing or wiping the noses of affected children.
Towels, food, drinks and eating utensils should not be shared while people remain infectious.
For more information contact your nearest Centre for Disease Control.
Last updated: 20 March 2020
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