Last updated on May 4, 2021.
Chickenpox is one of the most common childhood diseases. It typically causes the body to be entirely covered in blister-like rashes. In Hong Kong, chickenpox is the most reported infectious disease every year. Here is everything you need to know about chickenpox, reviewed by paediatrician Dr. Eddie Cheung.
What is chickenpox?
Chickenpox or varicella is a very common viral infection which mainly occurs in children under the age of 12. It is caused by varicella-zoster virus, leading to small itchy blisters on the skin. The virus may stay dormant in the body for years before being reactivated to develop a painful rash, shingles (Herpes zoster) later in life.
Complications can also occur, such as a secondary bacterial infection at wound sites, pneumonia, Reye’s syndrome (a severe condition that causes liver and brain damage) and inflammation of the brain.
That being said, chickenpox is a generally mild disease in children.The illness itself will resolve spontaneously. Full recovery takes 2-4 weeks. Most people will develop lifelong immunity against it after the first infection.
It is important for infected children to withdraw from all social activities, including childcare centres, schools and hobby classes, until there is complete crusting of the fluid-filled spots.
Incubation period: 10-21 days, usually 14-16 days.
Infectious period: Usually 1-2 days before the rash appears until all skin lesions have dried up. This is usually about 5-7 days.
How is chickenpox transmitted?
Chickenpox is highly contagious. Those who have never been infected or not received vaccines are more at risk. It can be spread through:
- Can be spread through droplets or air, e.g. contact with droplets of mouth or nose secretions or inhalation of aerosols (coughing or sneezing) of an infected person, or
- Touching the mucous membranes or fluid of the blisters.
Signs and symptoms of chickenpox
- Chickenpox usually starts with fever, overall discomfort and tiredness, sore throat or loss of appetite.
- Very itchy rashes then develop within 24 hours, which continue over several days. They first show up in clusters of flat red spots on the trunk and face, then move to the arms and the legs. These spot rashes can also be found inside the mouth, on eyelids or genital areas.
- The spots become fluid-containing blisters that may burst and discharge.
- The blisters crust and form scabs normally in about 1 week. New spots and blisters can keep popping up while others scab over.
- Scabs completely fall off within 1-2 weeks after the onset of the infection. The affected area of the skin may look lighter in colour for some time.
When should you see a doctor?
If you think your child has the symptoms, call a doctor first to avoid possibly spreading chickenpox at the clinic. They can then arrange an appointment for consultation, diagnosis and giving professional advice on proper management and isolation.
You should also speak to a doctor if your child
- is dehydrated
- has red, warm or painful rashes which could suggest a secondary bacterial infection
- experiences shortness of breath
How is chickenpox treated?
As mentioned, chickenpox typically heals itself without the need for seeking medical attention in children with a good immune system. Your child’s doctor may prescribe the following medications for symptomatic relief.
- Antihistamines for itchiness, e.g. cetirizine, diphenhydramine and loratadine.
- Paracetamol (aka acetaminophen) for fever or pain.
- Antiviral therapy may be considered depending on factors such as age, health condition and extent of infection. Examples include acyclovir.
- Calamine lotion for itchiness.
Other remedies or points to note include:
- Keep fingernails short or put on mittens or gloves to avoid scratching.
- Bathe in lukewarm water to relieve the itch. You can also add baking soda or uncooked oatmeal.
- Choose loose soft clothing.
- Drink plenty of water to avoid dehydration.
- Sugar -free popsicles or soft diet for mouth soreness.
- Do not have salty or spicy food as it can cause irritation to the lesions.
- Do not take aspirin. It is associated with Reye’s syndrome in children and adolescents.
- Do not take antibiotics. They will not help as chickenpox is not caused by bacteria but a virus.
Chickenpox vaccination in Hong Kong
Chickenpox can be prevented through vaccination. All children in Hong Kong receive two shots of varicella vaccines under the Hong Kong Childhood Immunisation Programme, which are given when they turn 1 and then at 18 months of age.
About 90% of people will acquire immunity after vaccination. It is still possible to get the illness even with vaccination, but the symptoms are often less severe and the duration is shorter.
Your child will usually not need to get vaccinated if they have had chickenpox before, because they will have lifelong immunity protecting them from it after the first infection.
Other ways to prevent contraction include:
- Maintaining good ventilation in an indoor area.
- Establishing a good personal hygiene routine, e.g. wash hands whenever necessary.
- Cleaning frequently-touched surfaces, for example furniture and door knobs, with 1:99 diluted household bleach.
Dr. Eddie Cheung 張蔚賢醫生 is a specialist in paediatrics. He received his paediatric training in Queen Mary Hospital and post-fellow paediatric cardiology training in Grantham Hospital/ Queen Mary Hospital. He is a Fellow of the Hong Kong College of Cardiology, the Vice President of Hong Kong Society of Paediatric Cardiology and Consultant of Hong Kong Association of Cleft Lip and Palate. He is currently working as Director of Paediatric Centre of HK Medical Consultants and serves as Infection Control Officer at the Hong Kong Adventist Hospital.