Health Advisory
BORDETELLA PERTUSSIS: PUBLIC HEALTH SURVEILLANCE, LABORATORY TESTING AND DIAGNOSIS

The Division of Public Health (DPH) is receiving an increasing number of calls and anecdotal reports of pertussis. Most of these reports are based on a clinical diagnosis without laboratory confirmation. DPH is not currently seeing an increase in confirmed reports of pertussis.

Without laboratory confirmation DPH is unable to properly investigate cases. This is of special concern when a hospitalized patient, healthcare worker, daycare, or school is involved and infection control measures are not implemented due to lack of laboratory confirmation

Public Health Surveillance

Pertussis is rapidly reportable in Delaware under the Regulations for Control of Communicable and other Disease Conditions. DPH receives reports from commercial and hospital laboratories, individual practitioners, hospitals, etc. Reports can be made by phone at 1-888-295-5156 or fax at (302) 223-1540.

Due to the communicability of the organism, DPH, Bureau of Epidemiology investigates every case that is reported. This investigation consists of:

• Verifying diagnosis;
• Establishing infection control mechanisms to prevent further transmission;
• Documenting effective treatment; and
• Enhancing surveillance in institutions, communities or families to identify additional cases.

From October 1, 2011 to February 24, 2012, DPH confirmed 9 cases of pertussis ranging in age from 1 month to 13 years---all from New Castle County. During the same time period last year (October 1, 2010 to February 24, 2011), DPH also confirmed 9 cases of pertussis ranging in age from 1 month to 18 years---6 from New Castle County and 3 from Sussex County.

DPH is asking physicians and other health care providers to verify suspect pertussis cases with laboratory testing. This will allow appropriate public health follow-up for patients, help identify outbreaks, and provide a better understanding of the disease trend in Delaware.

Disease Description

Pertussis, or whooping cough, is a highly communicable infectious disease caused by the bacterium, Bordetella pertussis. Pertussis is characterized by coughing paroxysms that are continuous without inspiration until the cough is finished and are often followed by a characteristic whoop and/or post-tussive vomiting. The incubation period is about 7-10 days (range 4-21 days). Illness onset is insidious, with symptoms similar to those of a minor respiratory infection (catarrhal period). During the first 1-2 weeks of illness, coryza with an intermittent non-productive cough is common; this period is followed by episodes of paroxysmal coughing which frequently last for several weeks (paroxysmal period). Pertussis may occur among persons at any age regardless of vaccination status and may be relatively common among adolescents and adults, although infants aged less than one year have the highest rates of reported disease.

Laboratory Testing and Diagnosis

• Although culture is the "gold standard" for laboratory confirmation, it must be collected before treatment is initiated and takes several days to grow. Additionally, it is not highly sensitive (60%).
• Due to the length of time to grow a culture, polymerase chain reaction (PCR) can be performed simultaneously on the same biologic samples as cultures. This allows for a quicker turnaround time while waiting for the culture to grow. PCR can also be performed in the absence of a culture as a confirmatory diagnostic tool. PCR is also known to be more sensitive than culture.
• Serology is not beneficial as a diagnostic tool for pertussis due to the necessity of collecting acute and convalescent specimens. Because of the insidious onset of pertussis, patients or their caregivers often delay seeking medical care and an acute serum cannot be obtained.
  • All suspect cases of pertussis should have a nasopharyngeal (NP) aspirate or swab obtained for culture and/or PCR from the posterior nasopharynx. (Throat and anterior nasal swabs have unacceptably low rates of recovery of B. pertussis)
  • NP specimens are obtained using a Dacron (not cotton) swab inserted slowly through the nostril to the posterior pharynx. Ideally, the swab is gently rotated for 10 seconds before withdrawing.
  • When planning to order both a culture and a PCR, insert both swabs simultaneously. The PCR swab goes back into the sterile container and does not require any transport media. The culture swab is placed in Regan-Lowe transport media.
  • Commercial laboratories (i.e. Mayo, LabCorp, Quest) can perform PCR and culture. Please follow their respective guidelines for collection and transport of the specimens.
  • Delaware Public Health Laboratory (DPHL) can perform PCR. DPHL does not perform B. pertussis culture. Testing performed at DPHL must be coordinated through the Bureau of Epidemiology (1-888-295-5156).

For Additional Information

• DPH, Bureau of Epidemiology at 1-888-295-5156. An epidemiologist is available 24/7.
• CDC - Pertussis: http://www.cdc.gov/pertussis/

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