BACKGROUND:
The number of reported pertussis cases has been increasing; however, few are confirmed because of the lack of culture or PCR results. In 2003, the New York City Department of Health and Mental Hygiene (NYCDOHMH), Vaccine Preventable Disease (VPD), Surveillance Unit received 356 reports of suspect pertussis cases; many of the cases were classified as probable because of the lack of diagnostic information. To improve the diagnosis of pertussis the NYCDOHMH, Public Health Laboratory (PHL) introduced PCR testing in 2004. Recently, NYCDOHMH, VPD investigated a case of pertussis in a member of a high school football team. PCR was used to determine if other team members were infected.

OBJECTIVE:
To show the value of PCR testing in a pertussis outbreak investigation where contacts were either asymptomatic or minimally symptomatic for pertussis.

METHOD:
A total of 46 nasopharyngeal swabs were collected from all the identified closes contacts. Specimens were sent to DOHMH PHL for PCR, DFA testing and culture.

RESULT:
46 team members were tested for PCR, DFA and culture. None met the clinical case definition, but 5(11%) had symptoms consistent with the catarrhal stage of pertussis. Among the 5 symptomatic patients, 4(80%) were positive by PCR and DFA, one (20%) was positive by culture. All asymptomatic children were negative by PCR, DFA and culture. Subsequent investigation identified one additional student in the same class who had symptoms consistent with pertussis; this person was previously treated with antibiotics by his physician and was not tested.

CONCLUSION:
Previously vaccinated adolescent may lack typical symptoms of pertussis and for this reason laboratory diagnostic testing may be necessary to confirm infection. In our investigation, the number of samples positive by PCR was higher than the number of samples positive by culture, illustrating a significant improvement in diagnostic yield over culture. Another advantage of PCR assay is the rapid turnaround time (few hours), which was enhanced its value as a significant tool to identify and control this outbreak and prevent further transmission within a short period of time.

LEARNING OBJECTIVES:
Use of PCR testing to identify and control of pertussis cases.