The thread installs the Intensified Smallpox Programme as a coupled machine — case-finding that can name a last patient, ring vaccination around that patient, and a two-year independent certification after which routine vaccination of the public could stop — rather than as a morality play about global cooperation. The unresolved question is which of those three was load-bearing, and therefore which repair a later eradication campaign would have to copy. The biology model says smallpox closed because there was no animal reservoir, a visible rash, and a heat-stable vaccine; you would not copy it onto a silent or vector-borne infection. The surveillance-containment model says the 1967 turn from mass coverage to finding cases is what closed it. The stop-condition model says the load-bearing act is WHA33.4: a certification that lets you shut the campaign down. Those are not substitutes. Polio copied the goal in 1988 and is still running in two endemic countries. Malaria copied a time-limited global campaign in 1955 and converted it to control in 1969. If wild poliovirus reaches zero and the Assembly then issues a stop-vaccination resolution of the WHA33.4 kind, the coupling travels. If it reaches zero and vaccination continues as a permanent programme, smallpox converted because the original problem was easy to see, and the comparison was always a category error.