Healthcare system disruption across WHO-declared PHEICs: a 4S comparative case analysis

Objectives To compare documented patterns of healthcare-system disruption and response across WHO-declared Public Health Emergencies of International Concern (PHEICs) using the established 4S surge-capacity framework (Staff, Stuff, Space, Systems) and an author-developed 12-indicator operationalization. Methods We conducted a structured comparative case analysis, not a systematic review of intervention effects, of all eight PHEIC events declared by WHO through 31 March 2026. The unit of analysis was the event, and the coded observations were operational occurrences documented in official sources. Twelve binary, unweighted author-developed indicators, three per 4S domain, were mapped to the four established domains. Activation required either one primary official source or two independent secondary sources meeting a prespecified threshold. Two reviewers independently assigned indicator-level codes, with disagreements resolved by consensus; indicators classified as Not Reported were combined with Not Activated. Activated indicators were summed within domains (range 0–3), and each observed configuration was assigned to one of four profiles using a fixed hierarchical rule sequence. Results All eight events activated at least one indicator, and external workforce mobilization (S1) and diagnostic bottleneck (T3) were documented in every event. COVID-19 was the only event activating all 12 indicators (systemic convergence). The two Ebola virus disease events shared an identical configuration of complete Staff, Stuff, and Systems activation with Space limited to temporary or repurposed facilities (workforce-cascade). H1N1 influenza, poliomyelitis, and mpox clade I formed the residual partial multi-domain category and did not share a common domain signature. Zika virus disease and mpox clade II met the limited-domain rule, with no Space-domain activation. Conclusion Public Health Emergencies of International Concern designation was not sufficient to identify a common pattern of documented health-system disruption. The typology is a provisional descriptive partition rather than a severity ranking, causal model, or predictive tool, and its residual category is heterogeneous by construction. Profiles are conditional on the documentary evidence base and the settings it represents; baseline health-system capacity was not incorporated, so the same pathogen could plausibly yield a different configuration elsewhere. The framework may offer a common vocabulary for discussing domain-specific preparedness needs under the revised International Health Regulations and the developing WHO Pandemic Agreement, but external validation is required.