Chicken pox: how does it affect children and grown ups?
Chickenpox and shingles are caused by the Herpes Zoster virus. It is also called the Varicella Zoster virus (varicella is the medical name for chickenpox).
Chickenpox is a mild disease affecting most children. It is most common in the winter and spring and nearly all cases occur in epidemics, once every three years or so. It is most common between the ages of two and eight.
The person is infectious from about two days before the rash appears until approximately five days after. It takes 11-20 days to develop symptoms after being in contact with the virus (the ‘incubation period’).
It is spread by direct contact with broken chickenpox blisters or by inhaling infected airborne droplets.
The rash takes the form of blisters, which burst and then scab over. Traditionally it was thought that the risk of passing on the infection was still there until the last blister had burst and scabbed. However, it is now recommend that children need only be excluded from school for just 5 days, as transmission has not been reported beyond day five of the rash.
After a chickenpox infection, the viruses remain dormant in the nervous system and are kept in check by the immune system. At any time later in life, but usually in adulthood, the viruses can be reactivated, causing shingles.
Chickenpox during pregnancy
If a woman is exposed to chickenpox or shingles when pregnant, there is no problem if she has already had chickenpox as a child as she is immune. 85% of women have antibodies to the chickenpox virus and therefore their baby is not at risk of chickenpox even if the mother develops shingles during pregnancy.
If the woman has not had chickenpox or is unsure if she has, she should see her doctor to arrange a test for antibodies as soon as possible.
If this shows she has not had chickenpox and has no antibodies, then chickenpox antibodies can be given to stop the disease developing. This is best given within 4 days (but is probably of use within 10 days) of coming into contact with the virus.
Symptoms of chickenpox
Chickenpox in children usually starts with a slight fever and a feeling of being unwell, sometimes with mild flu-like symptoms. A rash then appears in crops, typically behind the ears, under the arms, on the trunk, arms and legs.
It takes the form of small, itchy, red spots that become fluid-filled blisters within a few hours. They then dry out to form scabs in a day or two. Crops continue to appear for up to six days.
Chickenpox is almost always a very mild illness in children.
Chickenpox on adults: symptoms and complications
Chickenpox is rare but usually much more severe in adults. A high temperature, aches and pains and a headache often occurs a day or so before a rash appears.
The rash develops, with spots appearing in crops, which turn into small blisters and are itchy. They can appear anywhere on the body including in the mouth. Adults will often feel quite unwell, with a temperature, a dry cough, a sore throat and may feel sick for several days.
The blisters gradually dry up and scab over, usually they will completely gone after 2-3 weeks.
A person with shingles is contagious to people who have not had chickenpox. You cannot catch shingles from a person with chickenpox.
How to treat chickenpox?
Paracetamol may be taken to reduce fever. In severe cases an antiviral drug (acyclovir) may be prescribed, early in the course of the condition. Calamine lotion may be used to soothe the itchiness of the rash.
Complications of chickenpox in adults and unborn babies
Complications of chickenpox are rare in children.
In adults inflammation of the lung (pneumonia) is a rare complication affecting about 1 in 100 adults with chickenpox. Very rarely, an adult with chickenpox develops brain inflammation (Encephalitis).
As an adult the symptoms of chickenpox in the pregnant woman are unpleasant. In addition, when pregnant there is an increased risk (approximately 10%) of developing pneumonia.
For the unborn baby, there is 1-3% chance of abnormality if the chickenpox occurs within the first 20 weeks. The baby may develop congenital defects, mainly heart defects, deafness and cataracts. After 20 weeks there does not appear to be an increased risk of abnormality.
However, if the mother contracts chickenpox shortly before or after giving birth, the baby may develop a more severe form of chickenpox.