Definition: Whooping cough, or pertussis, is a highly contagious respiratory infection caused by Bordetella pertussis. It is characterised by severe, uncontrollable coughing fits often followed by a “whooping” sound during inhalation.
Epidemiology: Pertussis affects people of all ages but is most severe in infants under six months of age. Vaccination has reduced incidence globally, but outbreaks still occur, especially in under-vaccinated populations.
Significance: Can cause serious complications, particularly in infants, including pneumonia, seizures, and death.
2. Causes and Risk Factors
Causes:
Bordetella pertussis, a gram-negative bacterium, infects the respiratory tract, releasing toxins that damage ciliated epithelial cells and cause inflammation.
Risk Factors:
Lack of vaccination or incomplete vaccination.
Close contact with an infected person.
Infants, pregnant women, and immunocompromised individuals are at higher risk of complications.
3. Pathophysiology
Pertussis bacteria attach to and damage the cilia in the respiratory epithelium, impairing mucus clearance. The release of toxins, including pertussis toxin, leads to local inflammation and systemic effects. This results in the characteristic prolonged cough and whooping sound.
Severe coughing fits, often followed by a “whoop” sound during inhalation.
Post-tussive vomiting and exhaustion are common.
Convalescent Stage (weeks to months):
Gradual recovery with less frequent coughing spells.
Red Flags:
Apnoea (pauses in breathing) in infants.
Cyanosis, severe respiratory distress, or seizures.
5. Complications
Respiratory:
Pneumonia (most common cause of death in infants).
Atelectasis and bronchiectasis.
Neurological:
Seizures due to hypoxia or fever.
Encephalopathy from prolonged hypoxia.
Other:
Dehydration, malnutrition, or weight loss due to difficulty feeding.
Rib fractures or hernias from severe coughing.
6. Diagnosis
Clinical Features: Persistent coughing fits with or without the characteristic “whoop.”
Laboratory Tests:
Nasopharyngeal swab or aspirate for PCR testing (most sensitive in the first 3 weeks of illness).
Culture of B. pertussis (gold standard but less sensitive).
Serology: Measures pertussis-specific antibodies (useful in later stages).
Imaging: Chest X-ray to evaluate for complications like pneumonia or atelectasis.
7. Management Overview
Goals: Reduce symptoms, prevent transmission, and minimise complications.
Approach: Early antibiotic treatment, supportive care, and prophylaxis for close contacts.
8. Treatment Options with Cost (USD)
Antibiotics:
Azithromycin (preferred for infants): ~$20–$50 per course.
Clarithromycin or erythromycin: ~$15–$40 per course.
Trimethoprim-sulfamethoxazole (alternative): ~$10–$30 per course.
Supportive Care:
Hydration and oxygen therapy: ~$500–$1,500/day in hospital settings.
9. Advanced Treatment Options with Cost (USD)
Hospitalisation:
For infants with severe symptoms or complications like apnoea or dehydration: ~$1,000–$3,000 per day.
Mechanical Ventilation:
For respiratory failure: ~$10,000–$20,000 per admission.
10. Pharmacological Treatment
First-line: Azithromycin (5-day course) for patients of all ages.
Alternative: Clarithromycin (7-day course) or erythromycin (14-day course).
Supportive Medications:
Antipyretics (e.g., paracetamol) for fever.
Bronchodilators (occasionally used for wheezing, though efficacy is limited).
11. Medication Tables
Table 1: Doses and Side Effects
Drug
Indication
Dose
Common Side Effects
Azithromycin
First-line antibiotic
10 mg/kg/day for 5 days (max 500 mg/day)
GI upset, rash
Clarithromycin
Alternative antibiotic
15 mg/kg/day in 2 doses for 7 days (max 1 g/day)
Nausea, metallic taste
Erythromycin
Alternative antibiotic
40–50 mg/kg/day in 4 doses for 14 days
GI upset, prolonged QT
Paracetamol
Fever and pain relief
10–15 mg/kg every 4–6 hours
Rare liver toxicity (overdose)
Table 2: Brand Names and Approximate Costs (USD)
Drug
Brand Names
Approx. Cost
Azithromycin
Zithromax
$20–$50 per course
Clarithromycin
Biaxin
$15–$40 per course
Erythromycin
Erythrocin
$10–$30 per course
Paracetamol
Tylenol, Panadol
$5–$10 per pack
12. Lifestyle Interventions
Isolate the patient for 5 days after starting antibiotics to prevent transmission.
Maintain hydration with small, frequent sips of water or oral rehydration solutions.
Use a humidifier to ease breathing and soothe the throat.
Keep the patient in a calm and quiet environment to minimise coughing triggers.
13. Monitoring Parameters
Observe for reduction in the frequency and severity of coughing fits.
Monitor for signs of complications like dehydration, respiratory distress, or cyanosis.
Check for adherence to antibiotic therapy and resolution of infectivity.
14. Patient Counseling Points
Emphasise the importance of completing the full course of antibiotics to prevent transmission.
Educate on recognising warning signs like apnoea, severe breathing difficulty, or signs of dehydration, and seek immediate medical care if these occur.
Highlight the importance of vaccination for prevention.
Advise caregivers to take prophylactic antibiotics if they are close contacts.
15. Special Populations
In Infants (<6 months): Hospitalisation is often required due to high risk of complications. Use azithromycin as the first-line antibiotic.
In Pregnant Women: Azithromycin is safe; avoid erythromycin due to the risk of hepatotoxicity.
In Immunocompromised Patients: Aggressive management may be needed to prevent complications.
16. Prevention
Vaccination:
DTaP vaccine in infants and children.
Tdap booster for adolescents, adults, and pregnant women during each pregnancy (27–36 weeks gestation).
Post-Exposure Prophylaxis:
Close contacts, especially infants and pregnant women, should receive antibiotics (e.g., azithromycin).
Infection Control:
Isolate infected individuals during the contagious phase.
Practise good hand hygiene and respiratory etiquette.
17. FAQs
What causes whooping cough? Answer: It is caused by the bacterium Bordetella pertussis.
How is whooping cough transmitted? Answer: Through respiratory droplets from coughing, sneezing, or close contact.
What are the stages of whooping cough? Answer: Catarrhal stage (cold-like symptoms), paroxysmal stage (severe coughing fits), and convalescent stage (recovery).
How is whooping cough treated? Answer: With antibiotics like azithromycin and supportive care.
Can whooping cough be prevented? Answer: Yes, through vaccination and post-exposure prophylaxis.
Is whooping cough dangerous for infants? Answer: Yes, infants are at high risk of complications, including pneumonia and death.
What is the whooping sound in pertussis? Answer: It is caused by a forceful inhalation after a severe coughing fit.
How long does whooping cough last? Answer: Symptoms can persist for 6–10 weeks or longer.
Are vaccinated individuals protected from whooping cough? Answer: Vaccination provides protection but may wane over time, requiring boosters.
Can adults get whooping cough? Answer: Yes, especially if they are unvaccinated or their immunity has waned.
What is post-tussive vomiting? Answer: Vomiting after a coughing fit, commonly seen in whooping cough.
Is there a seasonal pattern to whooping cough? Answer: It can occur year-round but may increase in the late summer and autumn.
What is the role of the Tdap vaccine in pregnancy? Answer: It protects both the mother and newborn from pertussis.
Can whooping cough recur? Answer: Yes, reinfection is possible, but symptoms are usually milder in vaccinated individuals.
When should I see a doctor for whooping cough? Answer: If coughing persists, is severe, or is associated with breathing difficulty or apnoea.
