Pertussis (Whooping Cough)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Patient Advice

Definition

Pertussis, commonly known as whooping cough, is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. It is characterised by severe coughing fits followed by a "whooping" sound during inspiration. Pertussis is a notifiable disease in the UK, meaning healthcare providers must report suspected cases to public health authorities.

Aetiology

Pertussis is caused by Bordetella pertussis, a Gram-negative coccobacillus. It is transmitted via respiratory droplets during close contact with an infected person.

Pathophysiology

The pathophysiology involves:

• Colonisation of the Respiratory Tract: The bacteria attach to the ciliated epithelial cells of the upper airway.
• Toxin Production: Pertussis toxin inhibits immune responses and damages epithelial cells.
• Severe Inflammation: Leads to the characteristic coughing fits and airway obstruction.

Risk Factors

Key risk factors include:

• Lack of vaccination or incomplete vaccination schedule.
• Close contact with an infected individual.
• Infants under 6 months of age who are not yet fully vaccinated.
• Living in crowded conditions or attending daycare centres.

Signs and Symptoms

The clinical course of pertussis is divided into three stages:

1. Catarrhal Stage:

• Mild cough and runny nose.
• Low-grade fever.
• Highly contagious during this stage.

2. Paroxysmal Stage:

• Severe coughing fits followed by a "whooping" sound during inspiration.
• Post-tussive vomiting.
• Cyanosis or apnoea in severe cases, especially in infants.

3. Convalescent Stage:

• Gradual reduction in the frequency and severity of coughing fits.
• Symptoms may persist for weeks to months ("100-day cough").

Investigations

Key diagnostic tools include:

• Nasopharyngeal Swab or Aspirate: For PCR testing to detect Bordetella pertussis DNA.
• Serology: To detect pertussis-specific antibodies in cases with longer symptom duration.
• Full Blood Count (FBC): May show lymphocytosis, particularly in children.

Management

1. Supportive Care

• Encourage hydration and rest.
• Provide supplemental oxygen if needed for hypoxaemia or apnoea.

2. Antibiotic Therapy

• Macrolides:
  • Azithromycin: 10 mg/kg on day 1, followed by 5 mg/kg for 4 days (children).
  • Clarithromycin: 7.5 mg/kg twice daily for 7 days.
• Alternative for Macrolide Allergy: Co-trimoxazole for 14 days.
• Antibiotics are most effective if started within 3 weeks of symptom onset and can reduce transmission.

3. Isolation

• Advise isolation for the first 5 days of antibiotic therapy to prevent transmission.

Patient Advice

Key advice includes:

• Adhere to prescribed antibiotics and complete the full course.
• Avoid contact with unvaccinated or vulnerable individuals (e.g., infants, pregnant women).
• Ensure all household contacts receive prophylactic antibiotics as recommended.
• Keep up-to-date with vaccinations, including the pertussis booster during pregnancy.
• Recognise severe symptoms such as apnoea or cyanosis and seek immediate medical attention.