Abstract
<jats:p>Background: Timely detection and response to public health threats are essential to mitigating outbreaks. Kenya adopted a phased rollout of Event-Based Surveillance (EBS) in May 2021 to complement Indicator-Based Surveillance (IBS). We evaluated the sensitivity of EBS and the timeliness of both EBS and IBS systems for confirmed outbreaks across four Kenyan counties. Methods: We conducted a retrospective analysis of outbreak data from May 2021 to May 2025 in four counties in Kenya. We administered a structured questionnaire with the following variables: confirmed disease outbreak, dates of emergence, detection, notification, and initiation of each early response action, and the surveillance system that detected it. We also included bottlenecks and enablers for timely detection, notification, and response. The EBS sensitivity was summarized as a proportion, with the numerator being the outbreaks detected through EBS and total outbreaks as the denominator. Timeliness was measured using the 7–1–7 target, a global benchmark for measuring the timeliness of outbreak detection and response, where outbreaks should be detected within 7 days of disease emergence, notified within 1 day of detection, and initial response actions completed within 7 days of notification. The bottlenecks and enablers were summarized in a table. Results: We recorded a total of 28 confirmed outbreaks across the four years, of which 16 (57.1%, 95% C.I.: 34–72%) were detected through EBS. A total of 15 (53.6%) met the full 7–1–7 metrics. Among EBS-detected outbreaks: 100.0% were detected within 7 days of emergence, 81.3% were notified within 1 day after detection, and 68.8% had initial response activities completed within 7 days after notification. For IBS, 83.3% were detected within 7 days, 75.0% notified within 1 day, and 75.0% had initial response activities completed within 7 days. Five of the seven (71.4%) Anthrax outbreaks met all the metric targets. Detection and notification were enabled by community systems (trained health promoters, linkages, and awareness), information systems (hotlines, dashboards, and digital reporting), and response systems (sample referral and rapid response teams). Bottlenecks included limited reach, low suspicion, stigma, reporting downtimes, delayed escalation, and constrained response capacity due to funding, transport, personnel, and laboratory delays. Conclusion: The results demonstrate that EBS contributes significantly to outbreak detection and notification, while IBS contributes more to response. Therefore, there is a need to leverage EBS's strength in early detection and notification and IBS's better timeliness in response for a more timely system.</jats:p>