Pertussis

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DESCRIPTION

Pertussis (whooping cough), classically caused by Bordetella pertussis, is a highly contagious, protracted illness characterized by spasms of cough.

EPIDEMIOLOGY

  • Pertussis is one of the most highly communicable diseases with attack rates close to 100% in susceptible individuals exposed at close range.
  • Humans are the only hosts of B. pertussis.
  • Route of spread is via large aerosolized respiratory droplets.
  • Spread most commonly occurs during the catarrhal stage and first 2 weeks of cough onset.
  • Incubation period 5 to 21 days but typically 7 to 10 days
  • Pertussis occurs with seasonal peaks (late summer to autumn) and 3- to 5-year cycles of increased incidence of disease.
  • Adolescents and adults serve as major reservoirs and source of pertussis for infants.
  • Neither B. pertussis infection nor vaccination against B. pertussis is 100% protective.

Incidence

  • Pertussis infection rates have steadily risen since the early 1980s.
    • This is due to the combination of imperfect vaccines, waning immunity, vaccine refusal, low transplacental protection for infants, and undiagnosed individuals serving as reservoirs.
  • Infants <2 months of age have the highest age-related incidence.
  • Rates in school-age children and adolescents have been steadily increasing.
  • 10–30% of adolescents and young adults with prolonged cough (>2 weeks) have pertussis.

ETIOLOGY

  • B. pertussis, a small, nonmotile, fastidious, gram-negative coccobacillus, causes classic pertussis.
  • B. parapertussis causes a less protracted cough illness.

GENERAL PREVENTION

  • Infection prevention
    • Isolation of hospitalized patient: droplet precautions for 5 days after starting appropriate antimicrobial therapy or for 3 weeks after the onset of cough, if antibiotics were not given
    • Care of exposed people: Exposed individuals (all household contacts, other close contacts, other children in child care) should receive chemoprophylaxis (same agents and doses as treatment; see the following discussion) to limit secondary transmission, regardless of immunization status. Immunization should be given to all unimmunized and underimmunized children and to adolescents and adults who have not yet received the Tdap booster vaccination.
  • Immunization
    • All pertussis vaccines available in the United States are acellular vaccines in combination with diphtheria and tetanus toxoids.
    • Universal immunization of all children <7 years of age with DTaP vaccine is recommended per Centers for Disease Control and Prevention (CDC) and American Academy of Pediatrics (AAP) guidelines.
    • Undervaccinated children aged 7 to 10 years, all adolescents aged 11 to 18 years, adults aged 19 to 64 years, as well as certain adults aged ≥65 years should receive Tdap vaccine to help control the rate of infection in infants and young children.
    • Pregnant mothers should be vaccinated with Tdap during each pregnancy to protect their newborn infants; optimal time of vaccination is 27 to 36 weeks’ gestation.

PATHOPHYSIOLOGY

  • Tropism and replication are limited to the ciliated epithelium of the respiratory tract.
  • Biologically active substances such as pertussis toxin (PT), filamentous hemagglutinin, tracheal cytotoxin, adenylate cyclase, and pertactin are responsible for virulence of the organism, including attachment, ciliostasis, impaired leukocyte function, and local epithelial damage.

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