About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Caused by Bordetella pertussis (Gram-negative coccobacillus) — notifiable disease
- Three phases: catarrhal (1–2 weeks, coryzal), paroxysmal (2–8 weeks, coughing fits + whoop + vomiting), convalescent (gradual resolution)
- Diagnosis: anti-pertussis toxin IgG serology (if cough >2 weeks), or nasopharyngeal PCR/culture (if cough <2 weeks)
- Treatment: macrolide antibiotic (azithromycin 500 mg OD for 3 days) — reduces transmission but does NOT shorten symptoms if given late
- Prevention: UK routine vaccination (DTaP/IPV/Hib at 8, 12, 16 weeks + preschool booster) + maternal vaccination in pregnancy (from 16 weeks)
Overview
Pertussis (whooping cough) is a highly contagious respiratory infection caused by Bordetella pertussis. The toxins produced by the bacterium cause intense inflammation of the respiratory mucosa and impaired mucociliary clearance. The disease progresses through three phases: the catarrhal phase (1–2 weeks of coryzal symptoms — the most infectious period), the paroxysmal phase (2–8 weeks of paroxysmal coughing fits followed by an inspiratory "whoop" and often post-tussive vomiting), and the convalescent phase (gradual reduction in cough over weeks to months). The "whoop" may be absent in infants and adults. Infants <3 months are at highest risk of complications and death.
Epidemiology
Despite high vaccination coverage, pertussis remains endemic in the UK with periodic outbreaks every 3–4 years. A significant outbreak occurred in 2023–2024 with markedly increased case numbers. Vaccination protection wanes over time, so adolescents and adults can be infected and transmit to vulnerable infants. Maternal vaccination (offered from 16 weeks gestation) provides passive immunity to newborns before they can be vaccinated themselves. Pertussis is a notifiable disease.
Clinical Features
Symptoms
Paroxysmal coughing fits — clusters of rapid, forceful coughs without time to breathe between
Inspiratory "whoop" after a coughing paroxysm — may be absent in infants and adults
Post-tussive vomiting
Cough lasting >2 weeks (often 3–4 months — "100-day cough")
Apnoeic episodes in young infants (may be the presenting feature, without cough)
Signs
Often afebrile between coughing episodes
Subconjunctival haemorrhages (from forceful coughing)
Facial petechiae
Chest examination is typically normal between paroxysms
Investigations
First-line
Nasopharyngeal PCR or cultureIf cough <2 weeks duration — culture on Bordet-Gengou or charcoal agar (slow-growing); PCR is faster and more sensitive
Anti-pertussis toxin IgG serologyIf cough 2–12 weeks duration — single serum sample; diagnostic level confirms recent infection (not simply vaccination)
Second-line
FBCMarked lymphocytosis is characteristic (particularly in infants — WCC may exceed 100 × 10⁹/L)
CXRIf complications suspected (pneumonia, pneumothorax) — usually normal in uncomplicated pertussis
Management
UKHSA guidelines + NICE CKS1
Antibiotics
- Azithromycin 500 mg OD for 3 days (first-line for adults)
- Clarithromycin 500 mg BD for 7 days (alternative)
- Co-trimoxazole if macrolide-allergic
- Antibiotics reduce infectivity but do NOT shorten symptoms if started after the paroxysmal phase begins
- Effective within the catarrhal phase or first 21 days of cough onset
2
Supportive care
- Most cases managed at home
- Adequate hydration, small frequent meals (to avoid vomiting)
- Infants <6 months: admit to hospital for monitoring (risk of apnoea, feeding difficulties)
3
Public health measures
- Notify local Health Protection Team (notifiable disease)
- Prophylactic antibiotics for close contacts (especially if household contains unvaccinated infant)
- Exclude from school/work for 48 hours after starting antibiotics (or 21 days from symptom onset if untreated)
4
Prevention
- UK routine immunisation: DTaP/IPV/Hib at 8, 12, 16 weeks; preschool booster at 3 years 4 months
- Maternal vaccination: offered from 16 weeks gestation (ideally 16–32 weeks) — provides passive immunity to newborn
Complications
- Pneumonia: Most common cause of pertussis-related death (secondary bacterial infection)
- Apnoea and seizures: In young infants — can be fatal
- Rib fractures: From violent coughing in adults
- Subconjunctival haemorrhage: From forceful coughing
- Pneumothorax: Rare
UKMLA Exam Tips
- 1Paroxysmal cough + inspiratory whoop + post-tussive vomiting = pertussis
- 2Pertussis is a NOTIFIABLE disease
- 3Marked LYMPHOCYTOSIS on FBC is characteristic (especially in infants)
- 4Azithromycin 500 mg OD for 3 days is first-line treatment
- 5Antibiotics reduce transmission but do NOT shorten the cough if given after the paroxysmal phase starts
- 6Maternal vaccination from 16 weeks gestation protects newborns before their own vaccination
- 7"100-day cough" — pertussis cough can last 3–4 months
practicetest your knowledge on pertussisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — respiratory and beyond.
open q-bank