Surveillance & Reporting

Trends

Pertussis is nationally-notifiable and cases should be reported to the appropriate health department. Pertussis cases are reported by states to CDC through the National Notifiable Diseases Surveillance System (NNDSS). Although many pertussis cases are not diagnosed and therefore not reported, the surveillance system is useful for monitoring epidemiologic trends. The limitations of laboratory diagnostics make the clinical case definition essential to pertussis surveillance. It is important to determine duration of cough — specifically whether it lasts 14 days or longer — in order to determine if a person's illness meets the definition of a clinical case.

Case Definition

Pertussis cases are reported by states to CDC through the National Notifiable Diseases Surveillance System (NNDSS). Both probable and confirmed cases should be reported nationally. The most recent case definition (1997) for pertussis includes the following information:

Clinical Case Definition

A cough illness lasting at least 2 weeks with one of the following: paroxysms of coughing, inspiratory "whoop," or posttussive vomiting, without other apparent cause (as reported by a health professional).

This clinical case definition is appropriate for endemic or sporadic cases. In outbreak settings, a case may be defined as a cough illness lasting at least 2 weeks (as reported by a health professional).

Laboratory Criteria for Diagnosis

• Isolation of Bordetella pertussis from clinical specimen
• Positive polymerase chain reaction (PCR) for B. pertussis

Because direct fluorescent antibody testing of nasopharyngeal secretions has been demonstrated in some studies to have low sensitivity and variable specificity, such testing should not be relied on as a criterion for laboratory confirmation. Serologic testing for pertussis is available in some areas but is not standardized and, therefore, should not be relied on as a criterion for laboratory confirmation.

Case Classification

Probable: meets the clinical case definition, is not laboratory confirmed, and is not epidemiologically linked to a laboratory-confirmed case.

Confirmed: a case that is confirmed culture positive and in which an acute cough illness of any duration is present; or a case that meets the clinical case definition and is confirmed by positive PCR; or a case that meets the clinical case definition and is epidemiologically linked directly to a case confirmed by either culture or PCR.

• National Notifiable Diseases Surveillance System (NNDSS)
  1997 Case Definition: Pertussis (Bordetella pertussis) (Whooping Cough)
• Council of State and Territorial Epidemiologists (CSTE)
  CSTE 1997 Position Statement: Public Health Surveillance, Control, and Prevention of Pertussis
• CDC. Case Definitions for Infectious Conditions Under Public Health Surveillance
  MMWR May 02, 1997;46(RR10):1-55

Enhanced Pertussis Surveillance (EPS)

CDC has partnered with six states (CO, CT, MN, NM, NY, and OR) participating in the Emerging Infections Program (EIP) network to conduct enhanced surveillance of pertussis and other Bordetella species. EPS is characterized by enhanced case ascertainment and augmented data collection that goes beyond what is requested nationally through NNDSS. Participating sites collect isolates and specimens, when available, for further characterization at the CDC Pertussis and Diphtheria Laboratory. EPS sites also provide the infrastructure for conducting pertussis special studies including those aimed at evaluating pertussis prevention and control strategies.

 

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