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Whooping cough

Medicine > Infection

Background Knowledge 🧠

Definition

  • Whooping cough, also known as pertussis, is a highly contagious respiratory tract infection caused by the bacterium Bordetella pertussis.
  • Characterised by severe coughing spells that end with a “whooping” sound during inspiration.
  • Affects all age groups but is particularly severe in infants and unvaccinated individuals.
  • Can lead to serious complications, especially in young children.

Epidemiology

  • Worldwide, whooping cough affects 24.1 million people annually, with around 160,000 deaths.
  • Most deaths occur in infants under 6 months of age.
  • Incidence has decreased significantly due to vaccination but there has been a resurgence in recent years, even in vaccinated populations.
  • In the UK, pertussis is a notifiable disease, with periodic outbreaks occurring every 3-5 years.

Aetiology and Pathophysiology

  • Caused by Bordetella pertussis, a Gram-negative coccobacillus.
  • The bacterium adheres to the ciliated epithelium of the respiratory tract, releasing toxins that paralyse cilia and cause inflammation.
  • Toxins contribute to the characteristic cough and can lead to systemic effects.
  • Transmission is via respiratory droplets, with an incubation period of 7-10 days.
  • Infection confers incomplete and waning immunity, hence booster vaccinations are necessary.

Types

  • Catarrhal stage: Non-specific symptoms resembling a common cold, highly contagious.
  • Paroxysmal stage: Severe, spasmodic coughing fits, often with the characteristic “whoop.” Can last for weeks.
  • Convalescent stage: Gradual recovery over weeks to months, though coughing may persist.
  • Atypical pertussis: Milder form, more common in vaccinated individuals or partially immune persons.

Clinical Features 🌡️

Symptoms

  • Initially presents with mild, non-specific symptoms: rhinorrhoea, mild cough, low-grade fever.
  • Progresses to severe paroxysmal coughing fits, followed by the characteristic “whoop.”
  • Coughing may lead to vomiting, cyanosis, and exhaustion.
  • Symptoms can persist for several weeks, with milder cases sometimes misdiagnosed as bronchitis.
  • Adults may present with a prolonged cough without the “whoop.”

Signs

  • Inspiratory “whoop” after coughing fits, especially in children.
  • Post-tussive vomiting, common in children.
  • Subconjunctival hemorrhages from severe coughing.
  • Cyanosis and apnoea, especially in infants.
  • Absence of fever after the catarrhal stage.
  • Crackles or wheezing are uncommon.

Investigations 🧪

Tests

  • Nasopharyngeal swab or aspirate for culture is the gold standard, though PCR is increasingly used.
  • Serology can be used to detect antibodies in later stages or for retrospective diagnosis.
  • Full blood count may show lymphocytosis, which is suggestive but not diagnostic.
  • Chest X-ray may show perihilar infiltrates but is often normal.
  • Consider testing for other respiratory pathogens to rule out co-infections.

Management 🥼

Management

  • Supportive care is the mainstay: hydration, rest, and oxygen if needed.
  • Antibiotics (e.g., macrolides such as azithromycin) can reduce transmission if given early, but have limited impact on symptom duration.
  • Isolation is crucial to prevent spread, particularly in unvaccinated populations.
  • Hospital admission may be necessary for infants, those with severe disease, or complications.
  • Vaccination is key for prevention; booster doses are important in older children and adults.

Complications

  • Apnoea and respiratory failure, particularly in infants.
  • Pneumonia, either primary or secondary bacterial infection.
  • Seizures and encephalopathy due to hypoxia or toxin effects.
  • Rib fractures, hernias, or subconjunctival haemorrhages from severe coughing.
  • Malnutrition and dehydration from prolonged vomiting.
  • In rare cases, death, primarily in young infants.

Prognosis

  • Generally good in older children and adults with appropriate management.
  • Infants under 6 months are at higher risk for severe disease and complications.
  • Vaccination significantly improves outcomes and reduces incidence.
  • Cough may persist for weeks to months despite treatment.
  • Mortality is rare but more likely in unvaccinated infants.

Key Points

  • Whooping cough is a preventable but still prevalent disease, particularly dangerous for infants.
  • Timely vaccination and booster doses are essential to control outbreaks.
  • Early diagnosis and isolation can prevent transmission.
  • Management is primarily supportive, with antibiotics used to reduce transmission.
  • Complications can be severe, particularly in vulnerable populations, so close monitoring is essential.

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Infection