Pertussis (Whooping Cough)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Pertussis, also known as whooping cough, is a highly contagious bacterial infection caused by Bordetella pertussis. It leads to severe coughing fits and is particularly dangerous in infants. Pertussis is a notifiable disease in the UK, meaning all suspected cases must be reported to public health authorities.

Aetiology

The infection is caused by Bordetella pertussis, a gram-negative coccobacillus that spreads through respiratory droplets. It produces toxins that damage the respiratory epithelium, leading to prolonged coughing episodes.

Pathophysiology

Bordetella pertussis attaches to the respiratory epithelium and releases toxins that:

  • Inhibit ciliary function, leading to mucus accumulation.
  • Cause inflammation and oedema of the airways.
  • Trigger paroxysmal coughing episodes due to airway hypersensitivity.

Risk factors

  • Unvaccinated individuals (especially infants and young children).
  • Close contact with infected individuals.
  • Weakened immunity (e.g., elderly, immunocompromised patients).
  • Pregnant women in the third trimester (risk of transmission to newborns).

Signs and symptoms

Pertussis progresses through three stages:

1. Catarrhal Stage (1–2 weeks):

  • Mild cough.
  • Runny nose and nasal congestion.
  • Low-grade fever.

2. Paroxysmal Stage (2–6 weeks):

  • Severe, prolonged coughing fits.
  • "Whooping" sound during inspiration.
  • Post-tussive vomiting (vomiting after coughing).
  • Apnoea in infants (may be life-threatening).

3. Convalescent Stage (weeks to months):

  • Gradual improvement in symptoms.
  • Residual cough that persists for weeks.

Investigations

  • Nasopharyngeal swab: PCR test for Bordetella pertussis (most sensitive in early stages).
  • Serology: detects antibodies in later stages of the illness.
  • Full blood count (FBC): may show lymphocytosis (raised lymphocyte count).

Management

1. Antibiotic Therapy:

  • First-line: macrolides (e.g., azithromycin or clarithromycin) for 5 days.
  • Alternative: Co-trimoxazole if macrolides are contraindicated.
  • Antibiotics are most effective if given within the first 21 days of symptoms.

2. Supportive Care:

  • Encourage fluid intake to prevent dehydration.
  • Analgesia (e.g., paracetamol) for fever and discomfort.
  • Rest and avoidance of triggers that worsen coughing.

3. Preventative Measures:

  • Vaccination: pertussis vaccination is part of the routine UK childhood immunisation schedule.
  • Pregnancy immunisation: offered to pregnant women to protect newborns.
  • Post-exposure prophylaxis: consider for household contacts, especially if unvaccinated or at high risk (e.g., infants, pregnant women).

Referral

Refer to secondary care in the following scenarios:

  • Hospital admission:
    • Severe cases in infants (due to risk of apnoea and respiratory failure).
    • Dehydration or difficulty feeding.
    • Oxygen desaturation requiring respiratory support.
 
RespiratorymypanotesPertussis (Whooping Cough)