A Hong Kong Pediatrician’s Guide to Common Infectious Diseases in the Preschool Years

As a parent, it’s always hard to see your little one sick. It’s inevitable that they will pick up their fair share of coughs, colds and rashes in their early years. We spoke to Dr. Eddie Cheung 張蔚賢醫生 about the importance of building immunity and a guide to the most common early childhood disease to expect.
 
As a general rule, you should consult a doctor if you suspect illness in a child under 6 months old, your child is dehydrated (sunken eyes, not taking/keeping down liquids, extremely lethargic), has a high fever (under 6 months old: above 38 C; over 6 months: above 39 C), is immune-compromised, or has trouble breathing.
 
 

Building immunity

All these runny noses and strange rashes do have a positive side. As your child’s immune system is exposed to bacteria and viruses, they react to build immunity to that disease. Every time they’re sick, a little building block is added to their immune system. So although it’s heartbreaking to see them sick, it’s important that they are exposed to these small stresses on the immune system before they start school.
 
 

Which infectious diseases you can expect in Hong Kong in the pre-school years?

Chickenpox (Varicella) 水痘
Common Cold 傷風
Middle Ear Infections 中耳炎
Fifth’s Disease (Parvovirus) 第五病(細小病毒)
Hand, Foot and Mouth Disease 手足口病
Impetigo 膿瘡病
Influenza 流行性感冒
Meningitis 腦膜炎
Pinkeye/Conjunctivitis 結膜炎
Pinworms 蟯蟲
Respiratory Syncytial Virus (RSV) infection 呼吸道合胞病毒感染
Ringworm 癬
Roseola 玫瑰疹
Scarlet Fever 猩紅熱
Strep Throat 鏈球菌性喉炎
Whooping Cough (Pertussis) 百日咳
 
 
Important notes:
  • Incubation period refers to when the time between exposure to the illness and when symptoms appear.
  • Infectious period refers to the period when the disease can be spread. Sometimes diseases are infectious before symptoms appear.
  • Some of the infectious diseases below are included in the recommended Hong Kong Family Health Service (HKFHS) vaccination schedule.
 
 
 

Chickenpox (Varicella) 水痘

When should you see a doctor? Consult a doctor to confirm diagnosis, for professional advice on whether isolation is necessary, and for medicine for symptomatic relief. It’s important to be aware of and watch out for secondary bacterial skin infection as a complication.
 
Symptoms and cause: Viral. Fever and itchy skin rash which usually appears within 24 hours from fever onset. Rashes develop in croups on torso and then spread to face, arms and legs. They first appear as flat spots and later as small blisters.
 
Incubation period: 10-21 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.
 
Prevention and control
  • The Varicella vaccine is included in the HKFHS schedule. Children receive their first shots at 12 and 18 months, and a booster shot at 4-6 years. About 90% of persons acquire immunity after this vaccination.
  • Chickenpox is spread by droplets or air (coughing or sneezing), or direct contact with blisters.
  • Isolate children until all lesions have dried up. Usually this is 5-6 days after they appear.
 
 
 

Common Cold 傷風

When should you see a doctor? Consult your GP/Pediatrician if the child is under 1 year, unable to eat or drink well, having trouble breathing, or lethargic.
 
Signs and symptoms: Nasal congestion, coughing, sore throat. There may be fever. Many children will have up to 8 colds per year.
 
Incubation period: Dependent on the virus involved, usually 3-4 days.
 
Infectious period: Infectious while symptoms are present, usually around 1 week.
 
Prevention and control
  • Treat with rest and fluids.
  • If the child appears uncomfortable, particularly while sleeping, you can use children’s ibuprofen or acetaminophen, following instructions carefully. Saline drops or spray to remove excess mucus can also help children eat and sleep properly. Do not use over-the-counter cough and cold medications as dosages can be confusing and may lead to overdosing.
 
 
 

Middle Ear Infections 中耳炎

When should you see a doctor? Visit your GP/Pediatrician if there is ear pain with or without fever, with or without ear discharge.
 
Signs and symptoms: Can be caused by a virus or bacteria. Common symptoms are fever, difficulty sleeping and reduced appetite. Some children will have fluid or pus coming from their ear. The ear will be painful– nonverbal children will not always tug their ear but will be irritable and may be more upset lying down and/or may have trouble hearing. Ear infections can often be a result of a cold virus.
 
Incubation period: variable depending on the virus or bacteria involved, usually 3-4 days.
 
Infectious period: variable depending on the virus or bacteria involved.
 
Prevention and control
  • Avoid contact with sick people and practice proper hand washing to avoid colds.
  • GPs and pediatricians are often cautious about prescribing antibiotics for ear infections.
  • Children’s ibuprofen or acetaminophen can provide effective ear pain relief. Follow directions carefully.
 
 
 

Fifth’s Disease (Parvovirus) 第五病(細小病毒)

When should you see a doctor? Consult doctor to confirm diagnosis and take professional advice on isolation need. It’s important to seek medical attention if your child appears pale (severe anaemia can be one complication).
 
Signs and symptoms: A mild illness caused by a virus. Presents with a bright red rash on cheeks, known as “slapped cheek”. Rash can spread to arms, legs and chest and may get brighter if the child is warm. Fever, headache and achy joints in some patients.
 
Incubation period: Usually 4-14 days, can be up to 21 days.
 
Infectious period: No longer contagious once rash has appeared.
 
Prevention and control
  • Spread through saliva and mucus.
  • Practice proper hand washing.
  • Avoid contact with pregnant women as parvovirus can be spread to the fetus.
 
 
 

Hand, Foot and Mouth Disease 手足口病

When should you see a doctor? Seek prompt medical attention if your child has a persistent high fever, decrease in alertness or poor oral intake.
 
Signs and symptoms: Caused by a virus. Fever, sore throat, sores in the mouth, rash that may appear on hands, feet, face and/or buttocks. Not usually a serious illness. Generally, doesn’t spread or presents very mildly in adults.
 
Incubation period: 3-7 days.
 
Infectious period: The disease is most contagious during the first week of the illness and the viruses can be found in stool for weeks. Sick children should stay away from school or gatherings till all mouth sores have dried up and rash has disappeared.
 
Prevention and control
  • Spread through saliva, mucus and stool.
  • Virus can live for several hours outside the body so disinfecting shared toys can help prevent spread.
  • Cover nose and mouth when sneezing.
  • Wash hands after handling body secretions.
 
 
 

Impetigo 膿瘡病

When should you see a doctor? Impetigo needs medical attention and treatment. Usually only topical antibiotic cream is required but oral antibiotic is sometimes needed for more serious condition.
 
Signs and symptoms: Caused by bacteria. Honey-coloured blisters or sores around nose, mouth, arms and/or legs. Some may form large fluid-filled blisters. Rashes are usually itchy.
 
Incubation period: 1-3 days for group A Streptococcus, 4-10 days for Staphylococcus aureus infection.
 
Infectious period: Until sores have healed or after antibiotics have been taken for more than 48 hours.
 
Prevention and control
  • Spread through contact with infected person with or without visible lesions.
  • Exclude child from childcare/school until child has no fever, no lesions or 48 hours after antibiotics.
 
 
 

Influenza 流行性感冒

When should you see a doctor? Seek prompt medical attention if persistent high fever, decrease in alertness, troubled breathing or poor oral intake. Young kids < 2 years may be more vulnerable to complications. Often needs Flu test to confirm diagnosis.
 
Signs and symptoms: Caused by influenza A or B virus. Fever, cough, sore throat, congested nose, body aches and chills, headache, and sometimes diarrhea and vomiting.
 
Incubation period: 1-4 days.
 
Infectious period: 1 day prior to symptoms appearing, up to 7 days.
 
Prevention and control
  • Spread through mucus and saliva.
  • Practice proper hand washing.
  • Most children can overcome the virus without medication though some will require antiviral medication.
  • Seasonal Flu vaccination available for children 6 months or above through private clinics.
 
 
 

Meningitis 腦膜炎

When should you see a doctor? ESSENTIAL to see your GP or pediatrician if fever associated with headache, neck stiffness, photophobia (increased sensitivity to light) or decreased alertness are present.
 
Signs and symptoms: Can be caused by bacteria or a virus. Inflammation of the spinal cord and/or lining of the brain. High fever and chills, stiff neck, headache and/or vomiting. Some patients will also experience a rash, coma and/or seizures. Do not wait for a rash to seek medical attention.
 
Incubation period: Varies depending on whether it’s caused by bacteria or virus.
 
Infectious period: Varies depending on whether it’s caused by bacteria or virus.
 
Prevention and control
  • Spread via contact with mucus and/or saliva of infected person.
  • Practice proper hand washing.
  • Avoid sharing cups and tissues.
  • Many viral and bacterial causes of meningitis can be prevented by receiving vaccines. For example, vaccines against Pneumococcus, Mumps and Measles are available as part of the recommended HKFHS vaccinations. Vaccines against Haemophilus influenzae type B and Meningococcal types A, C, W and Y are available in private clinics.
 
 
 

Pinkeye/Conjunctivitis 結膜炎

When should you see a doctor? Seek medical advice if there is pain in the eyes, sensitivity to light or blurred vision, or pus-like eye discharge. Newborn with signs of conjunctivitis need to see doctor right away.
 
Symptoms and cause: Common infection caused by either bacteria or virus. Can sometimes be caused by allergens. Can affect one or both eyes. Irritated, sometimes itchy, watery, swollen eye with clear or yellow discharge that makes eyelashes sticky.
 
Incubation period: Varies depending on whether it’s caused by bacteria or virus.
 
Infectious period: Viral: while symptoms are present; bacterial: at least 24 hours after antibiotics have begun.
 
Prevention and control
  • Highly contagious. Spread through contact with eye discharge.
  • Avoid touching eyes.
  • Practice proper hand washing.
 
 
 

Pinworms 蟯蟲

When should you see a doctor? See a physician for treatment if you suspect pinworms.
 
Symptoms and cause: Caused by a small worm in the intestine. Signs of itchiness around the anus, particularly at night. Some have no symptoms.
 
Incubation period: 1-2 months or longer.
 
Infectious period: As long as there is a female pinworm depositing eggs.
 
Prevention and control
  • Spread by transfer of pinworm eggs from anus of infected person to mouth of another person or by contact with eggs.
  • Pinworm eggs can live outside the body (up to 2-3 weeks) so it’s important to wash bedclothes, sheets and toys.
 
 
 

Respiratory Syncytial Virus (RSV) 呼吸道合胞病毒感染

When should you see a doctor? See your doctor if your child is under 6 months, showing signs of trouble breathing, or dehydration.
 
Symptoms and cause: Caused by a virus. RSV infection is common from spring to winter in Hong Kong. Respiratory infection with very similar symptoms to a cold but can progress to bronchiolitis or pneumonia in young babies and children with weak immunity e.g. babies born prematurely or with congenital heart disease.
 
Incubation period: 4-6 days.
 
Infectious period: 3-8 days; people with weakened immunity may spread the virus as long as 4 weeks.
 
Prevention and control
  • Spreads through mucus and saliva.
  • Practice proper handwashing.
  • A drug (injection) is available to prevent serious RSV infection in certain infants and children who are at high risk.
 
 
 

Ringworm 癬

When should you see a doctor? Visit your pediatrician or GP if you suspect ringworm.
 
Symptoms and cause: Caused by a fungus (not a worm). Small, reddish, scaly circles on body or scalp, which may spread. Usually itchy.
 
Incubation period: Usually 1-3 weeks.
 
Infectious period: While lesions are visible.
 
Prevention and control
  • Spread by direct contact with infected person, animals or soil; or contact with contaminated objects such as combs, bedding, clothing, etc.
  • Apply either over-the-counter or prescription topical antifungal medication to the area and keep it covered.
 
 
 

Roseola 玫瑰疹

When should you see a doctor? The classic roseola rash appears 3-4 days after onset of fever. Fever may be the only symptoms initially. Seek medical advice to exclude other causes of infection if fever persists for 24 hours or more.
 
Symptoms and cause: Caused by a virus. Very common, especially in toddlers. Not typically serious. Presents with an abrupt onset of a high fever for 3-5 days. When the fever breaks, it is followed by a rose-coloured rash on the chest, abdomen, face and/or extremities that lasts for hours to days. Rash is typically not itchy. Occasionally may trigger febrile seizures especially in children 6-18 months of age.
 
Incubation period: 5-15 days.
 
Infectious period: Unknown.
 
Prevention and control
  • Exclude child from childcare during fever stage, but okay during rash stage.
  • Practice proper hand washing.
 
 
 

Scarlet Fever 猩紅熱

When should you see a doctor? Scarlet fever is treated with antibiotics so you will need to see your GP or pediatrician.
 
Symptoms and cause: Caused by the Group A Streptococcal bacteria. Bright red, ‘sandpaper’-like rash on the body. Sore throat, bright red tongue (strawberry tongue), swollen and red lips. Often occurs in individuals with strep throat.
 
Incubation period: 2-5 days.
 
Infectious period: At least until 24 hours after commencing antibiotic treatment.
 
Prevention and control
  • Spread through mucus and saliva.
  • Practice proper hand washing.
 
 
 

Strep Throat 鏈球菌性喉炎

When should you see a doctor? Strep throat is treated with antibiotics so you will need to see your GP or pediatrician.
 
Symptoms and cause: Caused by the streptococcal bacteria. Very sore throat and fever.
 
Incubation period: 2-5 days.
 
Infectious period: At least until 24 hours after commencing antibiotic treatment.
 
Prevention and control
  • Spread through mucus and saliva.
  • Practice proper hand washing.
 
 
 

Whooping Cough (Pertussis) 百日咳

When should you see a doctor? Consult doctor for infants < 6 months, having trouble breathing, decreased alertness or seizures.
 
Symptoms and cause: Caused by bacteria. Cold-like symptoms for 1-2 weeks with the cough becoming gradually more severe, sometimes with vomiting after coughing spells. Severe coughing can last for 1-6 weeks.
 
Incubation period: 5-10 days or longer.
 
Infectious period: During initial cold-like symptoms and for up to 3 weeks after coughing spells began.
 
Prevention and control
  • Highly contagious. Spreadable by coughs, colds and close contact.
  • Wash hands after coughs and sneezes, and dispose of tissues.
  • No longer infectious after 5 days of antibiotic.
  • Vaccine recommended by the HKFHS schedule at 2 months, 4 months, 6 months, 18 months, Primary 1 and Primary 6.
 
 
Dr. Eddie Cheung 張蔚賢醫生 graduated from the Faculty of Medicine of University of Hong Kong in 1997. He began working in the pediatric and neonatal units of Queen Mary Hospital and became a specialist in pediatrics in 2004. He has worked as a pediatric cardiology fellow in Grantham Hospital/ Queen Mary Hospital and obtained his Master degree in Medical Science (with distinction) from the University of Hong Kong in 2005. He is also a Fellow of the Hong Kong College of Cardiology, the Honorary Secretary of Hong Kong Society of Paediatric Cardiology and Consultant of Hong Kong Association of Cleft Lip and Palate. He is currently working as Consultant Pediatrician and Infection Control Officer at the Hong Kong Adventist Hospital.
This article was independently written by Healthy Matters and not sponsored. It is informative only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice.