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InfectiousICD-10: A37About 24 million cases worldwide per year; approximately 16,000 reported in the US annually

Pertussis

Also known as: Whooping Cough

Pertussis (whooping cough) is a highly contagious respiratory infection caused by the bacterium Bordetella pertussis. It is characterized by severe, uncontrollable coughing fits that often end with a high-pitched 'whoop' sound when the person inhales. While pertussis can affect people of all ages, it is most dangerous for infants too young to be fully vaccinated, in whom it can be fatal.

Symptoms

Early stage: mild cough, runny nose, low-grade fever (catarrhal stage, 1–2 weeks)
Paroxysmal coughing fits that may last for minutes
High-pitched whooping sound during inhalation between coughs
Vomiting after coughing episodes (post-tussive emesis)
Exhaustion after coughing fits
In infants: apnea (pauses in breathing), cyanosis, poor feeding
Cough that persists for weeks to months ('100-day cough')

Causes

  • Bordetella pertussis bacteria
  • Spread through respiratory droplets from coughing or sneezing
  • Highly contagious — can spread to 80–90% of susceptible household contacts

Risk Factors

  • Unvaccinated or incompletely vaccinated infants and children
  • Waning immunity in adolescents and adults (vaccine protection fades after 5–10 years)
  • Close contact with an infected person
  • Household members of newborns

Diagnosis

  • Nasopharyngeal swab for PCR testing (most sensitive in the first 3 weeks)
  • Nasopharyngeal culture (gold standard but less sensitive)
  • Serology (anti-pertussis toxin IgG) for late-presenting cases
  • Complete blood count may show marked lymphocytosis

Treatment

  • Macrolide antibiotics (azithromycin, clarithromycin, or erythromycin)
  • Early treatment (within the first 1–2 weeks) reduces severity and contagiousness
  • Post-exposure prophylaxis for close contacts
  • Hospitalization for infants with apnea, respiratory distress, or feeding difficulties
  • Supportive care (gentle suctioning, oxygen, IV fluids for infants)

Prevention

  • DTaP vaccination for infants and children (5-dose series)
  • Tdap booster for adolescents, adults, and pregnant women (each pregnancy)
  • Cocooning strategy — vaccinating all close contacts of newborns
  • Isolating infected individuals for 5 days of antibiotic treatment

When to See a Doctor

  • Persistent cough lasting more than 2 weeks, especially with coughing fits
  • Coughing episodes with whooping, vomiting, or turning red/blue
  • Any cough illness in an infant under 6 months
  • Exposure to a known pertussis case

Frequently Asked Questions

Related Conditions

Pneumonia

Respiratory

Bronchitis

Respiratory

Croup

Pediatric

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

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