Learning Objectives for this Presentation:
By the end of the presentation, participants will be able to understand the importance of modifying the current pertussis case definition for infants 0-2 months of age.

Background:
The pertussis current clinical case definition (CCCD) for all ages is an acute cough illness, minimum14 days, with paroxysmal coughing, inspiratory “whoop”, or post-tussive vomiting (PV). If not culture positive, the CCCD must be met for case classification. Research indicates infants 0-2 months of age with pertussis can exhibit different clinical symptoms from the definition and opportunities to prevent further transmission of disease are missed.

Objectives:
Develop, validate new clinical case definitions (NCCDs) for 0-2 month-olds, identify additional cases.

Methods:
From Los Angeles County 1997-2004 pertussis reports among 0-2 month-olds, NCCDs were developed using symptoms of lab-confirmed cases. False cases based on the CCCD were re-categorized using the NCCDs, and those with positive PCR results were used for sensitivity/specificity validation (SSV) of NCCDs.

Results:
During 1997-2004, 198 (37.9%) probable/confirmed pertussis cases were aged 0-2 months. Forty-seven were culture positive but didn't meet CCCD: coughed, maximum14 days (45% 8-13 days, 25% 4 days), 72% had paroxysms, 55.3% whoop, 55.3% apnea, 36% PV, 26% cyanosis. NCCDs developed for 0-2 month-olds: 1.Cough, minimum 4 days, with two or more of the following: paroxysms, apnea, “whoop”, PV; 2.Cough, minimum 8 days, with two or more of the following: paroxysms, apnea, “whoop”, PV. Of 31 cases 0-2 months of age, not meeting the CCCD, three were PCR positive. One met NCCD-1 and one NCCD-2. Due to small numbers, SSV could not be performed. Of the remaining 28 false-CCCD cases with negative/unknown PCR results, 25% (n=7) met NCCD-1, 28.6% (n=8) NCCD-2.

Conclusions:
At least 25.8% more probable/confirmed cases may have been identified with NCCDs, and upon investigation, additional epidemiologically-linked cases, emphasizing the importance of modifying the CCCD for 0-2 month-olds.