Does the Post-WHO-Exit IHR Architecture Survive Operational Stress?

Plain read: January 2026, the United States formally exited the World Health Organization under Executive Order 14155. The open question: in the next real-world cross-border outbreak, would international health coordination still work, or would the absence of US scaffolding cause measurable degradation? The MV Hondius hantavirus cluster (April-May 2026) became the first non-trivial test. The verdict (Report #84): the system worked. Symptom-onset to the World Health Organization notification took 26 days - faster than the average across five comparable pre-exit benchmarks (MERS Korea 9d, Diamond Princess 14d, Marburg Equatorial Guinea 40d, measles Samoa 45d, Ebola West Africa 90d; mean 39.6 days, z-score -0.42, 33rd percentile). South Africa NICD sequenced the virus. Senegal's Institut Pasteur de Dakar tested follow-up samples. ECDC deployed an EU Health Task Force expert directly to the ship. Africa CDC coordinated continental response. Switzerland, Singapore, Canada, the UK, Japan, the Netherlands, and Spain all integrated tracing. The US ran a parallel bilateral track for residents in five states (GA/CA/AZ/TX/VA) by direct intelligence sharing with European and African counterparts, conspicuously routing around the World Health Organization. The H1 thesis (IHR coordination degrades without US) is empirically falsified at this dimension. The architecture is multipolar. The US is no longer a load-bearing keystone for the IHR system - regional bodies (ECDC, Africa CDC) and Global South molecular-epidemiology infrastructure (NICD, Pasteur Dakar) substitute as primary coordinating authorities. This explicitly REJECTS the 'US-as-keystone-node' Layer-1 framing that pre-exit conventional wisdom assumed (Finding 30 records this as a Layer-1 REJECTION). Falsification triggers preserved (forward watch): (1) Engineered-genome discovery in the MV Hondius isolate (any furin-cleavage site, plasmid backbone remnant, or unnatural insertion) would instantly revive the engineered-origin hypothesis and reverse the routine-spillover null. (2) FOIA or whistleblower evidence that the US CDC was blocked from receiving epidemiological data specifically because of its the World Health Organization exit, with bilateral channels failing to track exposed citizens, would reverse the resilience verdict. (3) A secondary outbreak with reproduction number R>1 in a non-confined community setting (Tenerife, Cape Verde, US, UK, Switzerland, Singapore) linked directly to a disembarked MV Hondius passenger would void the containment-success assessment. (4) Repeat outbreaks at materially worse coordination intervals against a future five-event post-exit benchmark distribution would reactivate H1. Engine impact: the engine carries forward NO strong prior that future outbreaks will fail under post-EO-14155 conditions. What it carries instead is the bilateral-substitution architecture as the new operational default for US health diplomacy and the multipolar-IHR architecture as the global coordination baseline. Engine cross-references: `wh_eo_14155_who_exit`, `ihr_post_eo_14155_operational_test_node`, `africa_cdc_ascendancy_2026`, `mv_hondius_andes_cluster_2026`, `bst`.