Case definition for pertussis misses cases

Background Pertussis (whooping cough) is a vaccine-preventable respiratory infection, yet global resurgences persist despite routine infant immunization. Ongoing challenges include incomplete protection, waning immunity, particularly after the transition to acellular vaccines, and limitations in syndromic surveillance. The World Health Organization (WHO) and most national health authorities rely on clinical case definitions for pertussis surveillance; however, their diagnostic sensitivity and specificity, especially among children, remain uncertain. Study design and methods This retrospective evaluation assessed the performance of both WHO pertussis case definitions and modified definitions (apnea-inclusive, cough-duration-agnostic) against PCR-confirmed Bordetella pertussis infections in children aged ≤5 years, across sentinel sites in South Africa from 2017–2023. Surveillance covered outpatient clinics (influenza-like illness [ILI]) and hospitals (severe respiratory illness [SRI]). Children presenting with respiratory illness were tested for B. pertussis, and the sensitivity, specificity, and predictive values of case definitions were compared with PCR results. Key findings PCR detection rates were low: 0.7% among ILI and 1.6% among...