• B. pertussis is the most common aetiological agent of whooping cough and exclusively a human pathogen. B. parapertussis leads to less severe but similar symptoms.
• Typical pertussis infection lasts several weeks and consists of 3 stages.
  • Catarrhal stage: (1-2 weeks) rhinorrhea, mild fever (often absent), coryza and mild cough; infants may have apnoea/respiratory distress. Other  clinical clues to diagnosis include excess lacrimation and conjunctival injection and haemorrhage.
  • Paroxysmal stage: (2-6 weeks) increased cough with spells of repetitive usually dry cough, followed by sudden inspiratory effort (whoop) and post- tussive emesis.
  • Convalescent stage: (> 2weeks) decreasing frequency and severity of coughing episodes. Average duration of cough approximately 50 days.
• Adolescents and adults may have prominent hacking cough but lack characteristic whoop. Prior immunization can lead to atypical presentations

Potential complications

• Complications: pneumonia, urinary incontinence, rib fractures, hearing loss, development of hernias, sub-conjunctival haemorrhage, pneumothorax, aspiration, intracranial haemorrhage (in elderly), carotid artery dissection and death (rare in adults).
• In non-immune infants: pneumonia, apnoea, failure to thrive from post-tussive vomiting, seizures, encephalopathy and rectal prolapse.

• Nasopharyngeal swabs (use Dacron) for culture or PCR assay.
• Fastidious organism requiring special media for culture. Highest yield if performed within 3 weeks of cough onset or 4 weeks of symptom onset. Sensitivity and specificity of culture and PCR negatively affected by delayed transport to laboratory, vaccination, recent antibiotic use and prolonged illness. Culture remains the gold standard but suffers from low sensitivity. PCR-based assays increasingly used and may be more sensitive.
• Serology for pertussis toxin (PT) IgG or IgA performed in acute and convalescent specimens may support the diagnosis. A single high titer may be indicative of recent infection (e.g. >100U/ml anti-PT IgG).

A legally notifiable disease in Singapore. Notify Ministry of Health (Form MD 131 or electronically via CD-LENS) not later than 72 hours from the time of diagnosis.

• Empiric treatment recommended if the diagnosis is strongly suspected.
• Respiratory isolation for known cases. Suspect cases should be removed from the presence of young children and non-immunized infants until patients have received at least 5 days of antibiotics.
• Antibiotic treatment unlikely to shorten duration of illness if started more than one week after symptom onset, but is beneficial in shortening the infectious period and decreasing transmission.
• In vitro, most strains are sensitive to both macrolides and fluoroquinolones, but resistant to beta-lactams. Limited clinical experience with fluoroquinolones.
• Macrolides are the recommended first line of therapy. For adults and adolescents:
  • Azithromycin: 500mg oral x 1 dose then 250mg daily for 4 days; or
  • Clarithromycin: 500mg bd x 7 days;
  • Erythromycin: 500mg qid x 14 days;
  • (Alternative) Trimethoprim-sulfamethoxazole (Bactrim) oral bd x 14 days
• Infection in infants under age 6 months may require hospitalization due to complications of hypoxemia, apnoea or poor feeding.

Management of close contacts

• Administer antibiotic chemoprophylaxis if within 3 weeks of exposure.
• Use same drugs and duration as for treatment (see Management above).
• Review pertussis vaccination status of all contacts especially infants or adults caring for infants to ensure currency.
• Evidence for post-exposure immunization to prevent infection is limited.

• Routine childhood vaccination: primary immunisation at 3, 4 and 5 months (DPT); first booster (DPT) before school entry at 18 months with a 2nd booster (either Td or Tdap) at 10-11 years (primary V). See Appendix 2.
• Notification of all childhood immunisations to the National Immunisation Registry, Health Promotion Board, and post-vaccination adverse reactions to the Pharmacovigilance Branch, Health Sciences Authority. Immunity after childhood vaccination against B. pertussis wanes after 5 to 10 years and rarely lasts more than 12 years.
• Immunization of adolescents and adults aim to decrease the reservoir and transmission of pertussis in these populations and to infants.
• Tdap vaccine (tetanus-reduced diphtheria-acellular pertussis) is licensed for use in adults and adolescents. Its use should be considered in the following situations:
  • To replace the next dose of Td for adults aged 19 to 64 years as part of the 10-year Td boosting schedule.
  • Adults who have close contact with infants less than 12 months of age (e.g., parents, grandparents and child-care providers). The optimal interval between Tdap and the last Td is 2 years or greater, but shorter intervals are acceptable.
  • Women of childbearing age before conception or immediately postpartum prior to hospital discharge, if they have not previously received Tdap or whose last immunization is more than 2 yrs.
  • Healthcare personnel who have direct patient contact.