The idea that Gaeten Dugas was "patient zero" was thoroughly debunked soon after it initially circulated. The idea of "patient zero" sprang up because of a paper in the early 1980s (https://www.ncbi.nlm.nih.gov/pubmed/6608269) which implicated Dugas as patient zero. The paper tried to track down AIDS patients' sexual partners, and it included a graph of who had slept with whom. The graph had Gaeten Dugas at the middle of it, connected to all the other AIDS patients through a series of sexual links. Dugas was labelled as node "0", and the others were labelled "1" or "2", etc, depending on how many degrees they were removed from Dugas. (https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/AIDS_index_case_graph.svg/250px-AIDS_index_case_graph.svg.png).
The paper was mistaken. Although those early AIDS patients were all sexually connected to Dugas by at most a few degrees of separation, that does not imply that they acquired the infection from him. It's known now that HIV has a latency period of more than 8 years in young men before overt illness appears. Most of the early AIDS patients reviewed in that paper had directly or indirectly slept with Dugas only 10.5 months before symptoms started appearing in them, which implies that they had not been infected by him. Those AIDS patients who started getting sick in 1982 probably acquired the infection in the early 1970s, long before the sexual encounters with Dugas outlined in that paper. This has been known for more than 20 years.
The problems with the paper are: 1) a few gay men are highly sexually active and sleep with 100+ partners per year; 2) it takes many years for overt illness to appear; and 3) HIV is not highly infectious. As a result, those early AIDS patients may have had dozens of exposures to the virus over the years before encountering Dugas. Within the gay community there is a smallish subset who are hyper sexually active, and they are all sexually connected to each other, with only a few degrees of separation, at least within a particular city. At that point you're just playing the Kevin Bacon game; you can connect anyone to anyone else, and draw a graph however you like.