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454 Detection and Control of a Pertussis Outbreak in a Medical School and University Hospital

Sunday, April 3, 2011
Trinity Ballroom (Hilton Anatole)
Kouichi Tokuda, MD, PhD , Tohoku Univ Graduate School, Sendal, Japan
Makiko Yoshida, RPh, PhD , Field Epidemiology Training Program, National Institute of Infectious Disease, Tokyo, Japan
Tomimasa Sunagawa, MD, PhD , Infectious Disease Surveillance Center, National Institute of Infectious Disease, Tokyo, Japan
Kazumi Arise, RN , Kochi Medical School Hospital, Nangoku, Japan
Keiko Tanaka-Taya, MD, PhD , Infectious Disease Surveillance Center, National Institute of Infectious Disease, Tokyo, Japan
Hiroyuki Kunishima, MD, PhD , Tohoku Univ Graduate School, Sendal, Japan
Mitsuo Kaku, MD, PhD , Tohoku Univ Graduate School, Sendal, Japan
Kiyosu Taniguchi, MD, PhD , Infectious Disease Surveillance Center, National Institute of Infectious Disease, Tokyo, Japan
Nobuhiko Okabe, MD, PhD , Infectious Disease Surveillance Center, National Institute of Infectious Disease, Tokyo, Japan
Background: Health care workers (HCWs) would be under the risk of contracting pertussis in both their daily activities and communities since the immunity gained from DPT vaccination in their childhood would diminish in 10 to 12 years. In addition, booster immunization for adolescents and adults had not been introduced in Japan. In July 2007, we investigated a pertussis outbreak in a medical school and university hospital in Kochi prefecture in western part of Japan. No local epidemic had been reported from sentinel pediatricians.

Objective: To identify control measures on a pertussis outbreak, and to consider measures to prevent recurrence of the pertussis outbreak

Methods: We conducted a questionnaire survey which targeted the period from 1April to 8 August 2007, active surveillance (from 9 August to 8 September 2007), and active case finding for all students and staff members. A case was defined as a person who developed pertussis-like illness (PLI), such as paroxysms of cough and inspiratory whoop with a positive result of either culture or PCR test by a retrospective questionnaire survey and active case finding for all students and staffs. A retrospective cohort study was conducted to evaluate risk factors for infection.

Results: A total of 189 cases were detected (Incidence Rate [IR]=9.3%). Cases were started to report in early April, but index case could not be specified. The interview with cases in early stage of the outbreak revealed that most cases had contact with persons having PLI in communities. The IR in surgery-related departments was significantly higher than that in internal medicine-related departments (p<0.05). In general, the number of nurse-cases was strongly related to the number of student-cases (Correlation Coefficient [R2]=0.925). A cohort study showed that the risk in practical training in surgery was significantly higher in student-cases than in other students (RR=4.3, 95%CI=2.7-6.9). Cases rapidly decreased after introducing chemoprophylaxis, school closure (from 20 August to 14 September 2007) and restricting work of symptomatic staff members. There were no inpatient-cases due to secondary transmission.

Conclusions: Chemoprophylaxis, school closure and restricting work of symptomatic staff members were effective measures to prevent the further spread. This outbreak was probably reflected to local epidemics, which was not identified by sentinel surveillance system only by limited pediatricians. Case-based surveillance for pertussis including adolescents and adults should be introduced nationwide in Japan. Booster pertussis immunization for adolescents and adults should be considered, too.