Clinical Findings

  • Consider in any individual, even if immunized
  • Catarrhal period (1–2 weeks):
    • Illness onset insidious (coryza, mild fever, and nonproductive cough)
    • Infants can have apnea and respiratory distress
  • Paroxysmal period (2–6 weeks):
    • Paroxysmal cough
    • Inspiratory “whoop"

      pertussis_stages.png
      Stages of disease (weeks)

    • Posttussive vomiting
  • Convalescent period (>2 weeks):
    • Paroxysms gradually decrease in frequency and intensity


Diagnosis


CDC Clinical Case Definition

  • A clinical case is defined as a person:
    • Who has a cough illness lasting >2 weeks with one of the following (without other apparent cause)
      • paroxysms of coughing
      • inspiratory "whoop"
      • post-tussive vomiting
  • Laboratory criteria for diagnosis are:
    • Positive nasopharyngeal culture
    • Positive PCR reaction assay from nasopharyngeal swab
  • Confirmed case is defined as a person:
    • With an acute cough illness of any duration who is culture positive
    • Who meets the clinical case definition with laboratory confirmation by PCR
    • Who meets the clinical case definition and is epidemiologically linked directly to a case confirmed by either culture or PCR
  • Probable case is defined as a person:
    • Who meets the clinical case definition without laboratory confirmation or an epidemiologic link to a laboratory-confirmed case


Pertussis Laboratory Testing


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Note
  • Obtain PCR and culture with Dacron nasopharyngeal swabs or nasopharyngeal aspirate; swabbing throat and/or anterior nose yields unacceptable levels of recovery.
  • Pertussis DFA lacks sensitivity and specificity, should not be used as a replacement for culture, and is not recognized by CDC for confirmation of diagnosis
  • IgG level to pertussis antigen - either pertussis toxin (PT) which is most sensitive/specific, or filamentous hemaggutinin (FHA)
    • Methods:
      • Paired sera method: obtain acute level (within 2 weeks of cough) and convalescent level (4-6 weeks later); 4-fold increase confirms acute infection
      • Single sera method: a single high antibody titer obtained ideally >4 weeks after cough onset may suggest infection
    • IgG to pertussis FHA may be useful for B. parapertussis infection (IgG to PT is specific to B. pertussis)
    • Recent vaccination with pertussis and post-vaccination antibody levels do not interfere with diagnosis

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Optimal Timing for Testing




Treatment

  • Treat persons aged >1 year within 3 weeks of cough onset.
  • Treat infants aged <1 year within 6 weeks of cough onset.
  • Postexposure prophylaxis: administer course of antibiotic (same doses as in treatment schedule) to close contacts within 3 weeks of exposure, especially in high-risk settings

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References