Pertussis

Background

• “Whooping cough”. The “whoop” is caused on inspiration between coughs.
• Most common in kids < 1yo, because they haven’t completed the whole vaccine series, AND adults, who have waning immunity.
• One of the only vaccine preventable diseases that has increased in prevalence recently
• Up to 20% of adults with cough >2 weeks have serologic evidence of pertussis
• Bordetella genus (gram negative bacterium)

Pathophysiology

• Transmitted by aerosolized droplets, extremely contagious
• Infects ciliated respiratory cells (rarely goes hematogenous), creates toxins damaging respiratory epithelium.

Presentation

• Incubation period several days-3 weeks
• 3 stages:
  • Catarrhal phase: lasts 1-2 wks. Clinically indistinguishable from other URIs; dry cough starts near the end. Greatest infectivity phase.
  • Paroxysmal phase: lasts 2-4 weeks => fever improves, cough worsens. Staccato cough + whoop (present in 1/3 kids), post-tussive emesis (often in adolescents, adults). Infants can present as apnea. Pts often appear well between coughing episodes.
    • Petechiae, epistaxis, pneumothorax, and/or subconjunctival hemorrhage may occur due to high intrathoracic pressures during coughing.
  • Convalescent phase: lasts weeks-months; residual cough

Sequelae

• PNA superinfections, rib fractures, PTX, aspiration of gastric contents, CNS complications

Diagnosis

• WBC elevated in infants (20-100), adults may be WNL
• CXR with peribronchial thickening, atelectasis, and/or consolidation
• Nasopharyngeal swab can identify it in 3-7 days; often neg in adults.
• Cough for >2 weeks, post tussive emesis, feeling well otherwise, treat them empirically. Especially if infant or pregnant people at home.

Management

• Supportive. Suction in infants, hydration. Neonates with apnea should be admitted to the ICU.
• Antibiotics: don’t help much with severity or duration. Decreases infectivity.
• Peds: Azithromycin 10mg/kg (max 500mg/day) Qdaily x3 days
• Adults: Azithromycin 500mg Qdaily for 3 days OR clarithromycin 500mg BID x7 days
• Pregnant: Erythromycin 500mg QID x7 days
• Pts are considered infectious for 3 wks after start of paroxysmal phase, or after 5 days of abx (droplet isolation).

Post-Exposure Prophylaxis

• Prophylaxis for all household exposures of known Pertussis
• High risk people exposed to pertussis: infants, women in 3rd trimester of pregnancy, immunocompromised, severe asthma, people with close contact to infants <1year, people who work in neonatal ICUs / maternity wards.

Vaccination

• Tdap for adults, regardless of recent tetanus shot.
• DTaP for infants getting their first immunization.
• Vaccinate women during each pregnancy
• Immunity wanes 8 y after immunization. Often elderly will get the disease and transmit it to young unimmunized infants.

Sources

• Herbert, Mel; Takhar, Sukhjit. “Pertussis Update 2013”. Emergency Medicine Reviews and Perspectives. May 2013
• Marx et al. “Pertussis”. Rosen’s Emergency Medicine 8th edition vol 1 pg 1696-1699.
• “ Pertussis Postexposure Antimicrobial Prophylaxis”. Centers for Disease Control and Prevention. http://www.cdc.gov/pertussis/outbreaks/pep.html. Aug 28, 2013
• “Pertussis: Clinical Features”. Centers for Disease Control and Prevention. http://www.cdc.gov/pertussis/clinical/features.html. Sept 4, 2014