Whooping cough

Background

• Also known as pertussis
• Highly infectious disease caused by Bordatella pertussis
  • Produces pertussis toxin
  • Incubation usually around 7 days; spread via aerosol droplets; infectious for 3 weeks after initial symptoms
• Fortunately infrequent (1 in 1000 per year during ‘peak year’ which recur every 3-5 years) in the UK due to vaccination (DTaP at 2, 3, 4 months)
  • More common in infants who have not yet received full vaccination (or unvaccinated)

Presentation

• 3 phases of infection
  • catarrhal phase
    • dry, unproductive cough; may be preceded by prodromal symptoms typical of URTI (up to 7 days)
  • Paroxysmal phase
    • whooping (inspiratory gasp- may not be seen in adults), post-tussive (cough) vomiting is common in infants, generalised symptoms (can last a month or more)
    • between coughing fits, the patient is generally well
    • coughing fits are more common at night, can be triggered by cold/noise
      • in adults there may be associated autonomic features e.g. sweating, flushing; in children, it can cause cyanosis
  • Convalescent phase
    • Gradual improvement (can take 2+ months)

• NB Pertussis is a notifiable disease

Investigations

• Most cases are clinical diagnoses; but health protection may request laboratory confirmation via
  • nasopharygeal aspirate/swab
  • antipertussis toxin IgG
  • PCR positive

Management

• Consider admission to those who are seriously unwell e.g. cyanotic, apnoea, trouble breathing
  • Low threshold in infants <6 months
  • Particularly in cases with complications e.g. pneumonia
• Consider antibiotic treatment (macrolide- clarithromycin in <1 month; azithromycin + clarithromycin in older infants/children/adults; erythromycin in pregnancy) if symptoms started within 21 days
  • Important to treat in pregnancy to prevent transmission
• Health protection can consider offering antibiotic prophylaxis to those at risk (priority group) contacts e.g. those with pregnant women or baby in household.  Also offer immunisation