High pertussis circulation among infants, children and adolescents in Abidjan, Côte d’Ivoire

Abstract

Background Whooping cough due to Bordetella pertussis (BP) and/or B. parapertussis (BPP) is a highly contagious infection sometimes fatal for infants. Africa accounts for the largest share of cases and deaths worldwide. To evaluate pertussis circulation, we conducted a hospital-based prospective study (PS) including household contact-cases investigation (CCS) and a sero-epidemiological cross-sectional study (SECS). Methods The PS, in which Bordetella diagnostics (qPCR) were performed, included infants aged ≤6 months presenting with ≥5 days of cough associated with one pertussis-like symptom. CCS was performed using qPCR and serology regardless of clinical signs. In the SECS, serology was performed in children aged 3–15 years with primary pertussis immunization. Results Study took place in Abidjan between April 2019 and July 2021. In the PS, 187 infants with median age of 2.8 months were enrolled. A total of 42 (22.5%) were confirmed as positive, including 29 (15.5%), 4 (2.1%) and 9 (4.8%) of BP, BPP and BP/BPP coinfections respectively. Age <3 months, low BMI, apnea and inclusion period were identified as risk factors of infection. In the CCIS, 36 households were investigated, representing 158 people with median age of 21.4 years. BP and/or BPP infection was confirmed for 77/157 (49.0%). Twenty-nine households (81%) had at least one positive case. Sixty-seven (42.7%) contact cases were categorized as possibly contaminated, mainly siblings older than five years (25.4%). Twenty-seven contact cases were considered as possible contaminators, primarily mothers (26%). In the SECS, 444 people were enrolled. Two hundred and thirty-eight (53.6%) and nine (2.0%) children had received one and two boosters, respectively. A positive serology was observed in 96 (21.7%) of children and adolescents. Conclusion Our study highlighted high circulation of pertussis. Barriers to accessing boosters recommended by WHO need to be overcome. Laboratory capacities are key at individual level and to build an effective surveillance system.