Evaluation of reported cases of pertussis: epidemiological study in a large city in Spain

We retrospectively analysed the incidence rate of reported cases of pertussis in Barcelona during 2009-2012 according to age, sex, type of medical centre and vaccination status. We included 748 confirmed or suspected cases, 613 (82.0 %) of which were confirmed by laboratory testing and the remaining 135 (18.0 %) by epidemiological evidence. The highest reported incidence of pertussis was amongst <1 year olds [96.1 per 100,000 person-years, 95 % confidence interval (CI): 84.3-109.1]. The majority of confirmed and suspected cases were reported in 2011 and 2012, and the total incidence (confirmed or suspected) was 6.3 (95 % CI: 5.6-6.9) and 4.2 (95 % CI: 3.6-4.7) per 100,000 person-years, respectively. Incidence increased significantly (P = 0.001) in 2011-2012 compared with 2009. Most confirmed cases occurred in children <1 year old (87.9 %). Cases were confirmed by real-time (RT)-PCR (87.5 %; 95 % CI: 81.3-87.6) and bacterial culture (13.7 %; 95 % CI: 11.0-17.1). We recommend performing RT-PCR in suspected cases with no epidemiological link to a confirmed case.