Chickenpox (varicella) is an acute infectious disease caused by the varicella-zoster virus. It is predominantly a childhood disease affecting children between five to ten years old. It is extremely contagious, especially among young children and in the early stages of rash eruption. Infection confers life-long immunity. However, the chickenpox virus may remain dormant and may recur years later as herpes zoster (shingles).

Mode of Transmission

• Direct person-to-person contact.
• Through air-borne droplets or air-borne spread of the discharge from the respiratory tract.
• Indirectly from the articles freshly soiled by discharges from the infected persons' lesions.

Incubation Period

About two to three weeks.

Period of Communicability

As long as 5 days (but usually 1 to 2 days) before onset of rash and continuing until all lesions are crusted (usually about 5 days after rash appears).

Clinical features

• May have low-grade fever.
• A skin rash develops on the child's scalp and body, which spreads to the face, arms and legs with formation of vesicles over a period of 5 days. The rashes occur mainly on the trunk.
• The vesicles are itchy.
• The vesicles dry up and form a scab in about three days.
• The patient usually recovers in about two to four weeks.

Complications

Chickenpox is a mild disease and is usually self-limiting. However, those with low body resistance are most likely to suffer from complications such as skin infection, scarlet fever, pneumonia and encephalitis. Newborn babies who develop chickenpox can result in severe generalized illness and even death. Infection in early pregnancy may be associated with congenital malformation of the foetus.

Tips for General Management

• Drink plenty of fluid and take 'fever-lowering medicine' as prescribed by the doctor.
• Eat nutritious and easily digested food such as fish and beef congee .
• Scratching the skin lesions may introduce infection. Therefore, have the sick child to wear clean cotton gloves while sleeping and apply 'anti-itching lotion' as prescribed by the doctor to avoid scratching of the skin lesions.
• Closely monitor your child's condition. If he/she persistently runs a high fever, refuses to eat or drink, vomits, and deteriorates in mental state, you should bring him/her for medical advice immediately.
• Parents should also closely watch out for whether other children in the household have also got infected by chickenpox.
• Sick persons should not come into contact with pregnant women and persons with low body resistance.
• The sick child should stay at home and be excluded from school or kindergarten for around 1 week or until the skin lesions crusted to prevent spreading the disease to others.
• For the school, if there is a case of chickenpox occurring among the students, other parents should be informed to look out for early signs of the disease among their children. The school should inform parents of children suspected to have chickenpox to take sick leave and seek medical care.

Preventive Measures

• Maintain good personal and environmental hygiene.
• Keep hands clean and wash hands properly.
• Chickenpox vaccine is available in Hong Kong. About 90% of persons who receive the vaccine will acquire immunity. Parents can approach their family doctors for further advice and information.