The last outbreak of smallpox in Europe was in Yugoslavia in 1972.
The deadly disease was viewed as eradicated in the first and second worlds, and the W.H.O. had been fighting it in the third world.
Patient zero, an Albanian Muslim from Kosovo by the name of Ibrahim Hoti, was infected in Saudi Arabia as he was making the Hajj, he recovered because he was vaccinated.
People who were in contact with him were infected, that's true.
However none of his 11 children were infected (let's not talk about the demographics of Kosovo Albanians, that's another topic, and i'm tired of it), which lead some epidemiologists to believe it was a case of biological warfare, but that's in the realm of conspiracy theory, and there doesn't seem to be a clear culprit (neither USA nor USSR).
He infected Latif Mumdžić, who sought medical help, but the local doctors couldn't diagnose him and sent him to Belgrade (but to Novi Pazar and Cacak before that).
At first the doctors misdiagnosed him with an allergic reaction to penicillin, soon other symptoms appeared.
35 people at the hospital were infected, 9 of whom were doctors (8 of whom died).
Simultaneously ~140 cases of smallpox were reported in Kosovo.
Strict quarantines were established and mass vaccinations ensued. People were getting vaccinated in hospitals, in schools, in factories, in the streets and in the fields (my mom told me specifically that she was vaccinated at school).
The W.H.O praised the Yugoslav regime for quick and decisive (read, brutal and panicked) action, which quickly contained the disease.
There is a great movie from 1982 based on this event (of course, it's not a documentary, it's an epidemic movie and it takes creative liberties). The writer/director obviously knew a lot about the danger of evolving diseases, and he masterfully critiqued communism (and the Yugoslav government), not only through the actions of the government in the movie, but comparing it to the very disease.