最後更新日期 四月 30, 2021.
In recent years, a resurgence of whooping cough (pertussis) has been observed in countries with high vaccination coverage, such as Australia, Japan, the United States and a number of European countries. Regionally, there have also been significant increases in the number of reported pertussis cases in the Mainland including Guangdong Province. In Hong Kong, there has been a surge in notified pertussis cases in the past 3 years. The number of pertussis cases recorded by the CHP has increased from 20 to 50 per year during 2011-16 to 69 cases in 2017, and further to 110 cases in 2018. Pertussis is a serious infection that brings violent coughing spells lasting for weeks to months. Here is everything you need to know about whooping cough, reviewed by pediatrician Dr. Eddie Cheung.
What is whooping cough?
Whooping cough, or pertussis, is a contagious respiratory infection caused by the bacterium Bordetella pertussis. It causes persistent coughing due to the inflammation and swelling of the airways.
Infants younger than 6 months without immunisation, and children between 11 and 18 years whose immunity starts to wear off are mostly affected. The diagnosis is done by looking at the signs and symptoms, by performing a physical examination, by doing blood tests and by testing mucus from the nose or throat.
Whooping cough gets its name because of the “whoop” sound produced when people breathe after coughing. The Chinese name “100-day cough”, which is pretty self-explanatory, illustrates the duration of the infectious disease (about 2-3 months).
Roughly 50% of patients under the age of 1 are hospitalised and those below 6 months are at greater risk of developing complications, including pneumonia, seizures, difficulty breathing and brain damage. The mortality rate is low with prompt and appropriate treatment.
Vaccines are available for prevention. Keep your child away from nurseries, schools and daycare centres for 48 hours after taking antibiotics or 3 weeks after the coughing spells start.
Incubation period: ranges from 4-21 days, usually 7-10 days.
Infectious period: during initial cold-like symptoms and for up to 2-3 weeks after coughing spells began or about 5 days after commencing antibiotic treatment.
How is whooping cough transmitted?
Whooping cough is spreadable by close contact with someone with the infection. The bacteria can be transmitted by droplets produced by coughing, sneezing or even laughing. Having close contact in a confined area or touching surfaces and objects contaminated with infectious droplets can transmit the disease.
Family members and friends are therefore at greater risk of developing whooping cough.
Signs and symptoms of whooping cough
It starts like a common cold, causing symptoms like a runny nose, a stuffy nose, sneezing, a mild cough and a slight fever.
After 1-2 weeks, the cold symptoms will get better. During that same time, coughing spells increase in severity and frequency, lasting a few minutes at a time. They are more common at night. Children will usually feel well between spells.
During a coughing spell, gagging or difficulty breathing can occur. Your child may also vomit and feel tired from coughing so hard. Not everyone will make the characteristic “whoop” sound when they cough. Many babies with Whooping Cough do not cough at all. Instead, temporary cessation of breathing can occur and their lips and skin may turn purplish or bluish due to lack of oxygen.
After 2-4 more weeks, the cough improves but likely won’t stop completely for several weeks (up to a few months).
Children who have been vaccinated generally experience milder symptoms for a shorter period of time.
When should you see a doctor?
Visit your doctor if your child shows symptoms or has been in close contact with someone infected even if they have been vaccinated.
Seek immediate medical attention if they have a whooping cough and
- develop a high fever
- persistent vomiting, e.g. after coughing
- struggle to breathe
- are dehydrated, e.g. thirst, a lack of energy, dizziness, confusion, and dry skin or lips
- get complications, e.g. seizures
- the cough becomes more severe and frequent
- their skin or lips turn purple or blue
How is whooping cough treated?
Early treatment of pertussis is very important. The earlier a person, especially an infant, starts treatment the better. If a patient starts treatment for pertussis early in the course of illness, during the first 1 to 2 weeks before coughing paroxysms occur, symptoms may be lessened.
Antibiotics help fight off the bacteria, shorten the length of the illness, and most importantly prevent the transmission to others. Supportive treatment e.g. oxygen supplement may be required depending on the child’s condition.
If the Whooping Cough lasts for more than 3 weeks
Your child usually won’t need treatment because the infectious period should have been over, and medications are not of much help at this stage.
Note that antibiotics do not reduce coughing. Cough syrups are unlikely to be helpful with managing the cough in children with pertussis.
What to do at home to feel better
- Plenty of rest
- Ensure fluid intake
- Avoid cough triggers, e.g. cigarette smoke
- Use a cool-mist vaporizer to soothe irritated air passageways
- Prepare small meals every few hours to avoid vomiting
Vaccination for whooping cough (DTaP)
Under the Hong Kong Childhood Immunisation Programme, all children in Hong Kong receive 5 shots of DTaP-IPV (Diphtheria, Tetanus, acellular Pertussis & Inactivated Poliovirus Vaccine) at 2, 4, 6, 18 months and at around 6 years old. Reduced dose vaccine is recommended for primary 6 students as protection may fade.
To provide direct protection for infants against pertussis, pregnant women are recommended to receive one dose of acellular pertussis-containing vaccine during each pregnancy (preferably before 35 weeks of gestation regardless of previous vaccination and natural infection history against pertussis.
Although vaccines are not 100% effective, they offer good protection and the disease is milder in those who are infected after immunisation.
Practicing good personal hygiene
E.g. regular hand-washing with soap and water, covering nose and mouth with a tissue during coughing or sneezing, and putting used tissue into a rubbish bin immediately.
Possible need for antibiotics
Whooping cough is very contagious. Ask your doctor whether your child and other family members, especially pregnant women, should get antibiotics for prevention (post-exposure prophylaxis) if someone in the household has it.
Maintaining good environmental hygiene
E.g. regular cleaning and disinfection of frequently touched surfaces and shared objects 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.