Optimizing the implementation of case-area targeted interventions during cholera outbreaks with context-specific delivery mechanisms.

Cholera, a severe fecal-oral disease, disproportionately affects the poorest communities who lack access to safe water and sanitation. Individuals living in the same household, or within a few hundred meters, of a patient are at increased risk of infection. Thus, during cholera outbreaks, targeted response strategies, such as case-area targeted interventions (CATIs), provide health (e.g., vaccination and antibiotic prophylaxis) and water, sanitation, and hygiene services for affected households and at-risk neighbors living in a defined ring. Previous research on CATIs has focused on impact and effectiveness, and less on implementation processes. As cholera outbreaks occur in diverse settings with differentiated challenges, we investigated how CATI and CATI-like mechanisms can be best used and adapted. Drawing on 43 peer-reviewed articles and gray literature sources retrieved through a narrative review, and 15 key informant interviews conducted using a snowball sampling approach, we identified 27 CATI or CATI-like experiences across 15 countries in Africa, Asia, the Caribbean, and Middle East between 2004 and 2024. Four delivery mechanisms were identified: CATI, pre-CATI, case-cluster, and health-facility-based interventions (HBI). Challenges to implementation included: delays in response; difficulty accessing populations; resource shortages to initiate, maintain, or scale up response; overwhelmed response capacity; limited skills and knowledge; low uptake and acceptance; weak coordination; poor reporting and monitoring; and sustainability concerns. Implementers adapted delivery to overcome challenges, particularly in outbreaks with high case-loads and in insecure and hard-to-reach contexts by ensuring readiness and early activation, strengthening local actors' capacity, optimizing resources, adjusting ring sizes, and prioritizing cases. Based on these results, we developed a practitioner-centered framework to optimize programmatic implementation through context-specific delivery mechanism and ultimately decrease cholera incidence.