Before we talk about AIDS we need to talk about its precursor, HIV, and the precursors of that precursor. It's actually pretty contentious who the first recorded HIV-positive individual may have been, just because being able to prove such a thing through tissue samples would be a huge assist to our understanding of the earlier forms of HIV -- there are a number of individuals who (by way of tissue samples and identifiable symptoms recorded pre-1981) have retroactively become known to science this way as likely HIV-positive people. Previous strains of the virus now categorized as HIV have been dated back to the early 1900s in central Africa, and at some point in the virus' development it bridged from non-human primates to people. There's a lot to suggest that this precursor to later strains of HIV was circulating for a while in the 1950s and 1960s, among humans in and around Cameroon -- this is the origin of the theory that humans first contracted an early form of HIV from primate bushmeat, and that the transmission of HIV was furthered by the effects of the presence of 20th century colonial interests in Africa. If these precursor strains of HIV had developed in the 13th century, or the 17th century, they might well have been transmitted from primates to humans and then circulated among locals, but they wouldn't likely have developed into an international epidemic as they did in the 20th century -- the circumstances of late-19th/early 20th century colonialism brought an influx of transient non-locals to central Africa (among many, many other things) and established conditions of sexual exploitation that allowed HIV to circulate.

Meanwhile in America, a Missouri teenage boy (Robert Rayford) manifested a variety of symptoms we now traditionally associate with full-fledged AIDS way back in 1969, including Kaposi's sarcoma lesions, and ultimately died due to pneumonia, an opportunistic infection also associated with AIDS. All these things, two decades later, would have been immediately recognized by medical staff as signs of AIDS, but at the time they were believed to be symptoms of an unfamiliar and novel strain of an already-known sexually-transmitted illness like gonorrhea. At 16 Rayford was not an international traveler, a hemophiliac/organ or blood donation recipient, or an IV drug user; he likely contracted HIV earlier in life through sexual abuse. But how did Rayford's sexual abuser contract HIV? There it might be useful to look at the case study of Arvid Noe, an international traveler and frequenter of prostitutes who is believed to have contracted sexually-transmitted HIV in the course of his work in Central Africa and subsequently have transmitted it to sexual partners in Western Europe. It seems reasonable for me to believe that there was some earlier equivalent of Noe out there -- that at some point in the 1950s-1960s, someone from the community of unwittingly HIV+ people in Cameroon transmitted HIV to someone in the US who then transmitted it to whoever was having sex with Rayford, give or take a couple people in between. Any of the people in that chain before Rayford might have later progressed to AIDS without coming to the attention of doctors, or without the medical profession making the link at the time between all the various sufferers. So by the 1960s, HIV was sexually-transmissible between humans, and by the late 60s/early 70s HIV was capable of progressing rapidly or less-rapidly into AIDS, but it wouldn't achieve the complete set of qualities associated with later strains of the virus or come to the attention of CDC researchers as a discrete condition with a discrete constellation of symptoms until the early 80s. The reason this happened in America is likely because AIDS had arrived there decades ago, having had time to circulate, and because the medical infrastructure was sufficiently robust in a way it wasn't in mid-20th-century central Africa under colonial rule. (Not robust enough to keep HIV/AIDS from progressing to a global epidemic, but better.) HIV as we know it -- as a virus that can be transmitted between humans through fluid transmission routes like sex and that progresses into AIDS, acquired immunodeficiency syndrome -- is a 20th century phenomenon, both in those specific terms and in terms of its presentation. But it had conceptual precursors in terms of other venereal diseases, and in the very concept of "venereal disease" itself. We can talk about sexually-transmitted illnesses that were extremely debilitating and highly dreaded prior to the 20th century -- the constellation of symptoms and conditions that make up Early modern syphilis/French pox/etc. -- in terms of how they relate to AIDS in the 20th century, but the AIDS crisis as it developed in the United States was a product of American medical infrastructure and American politics around drug use and marginalized identities. It couldn't have happened earlier in the same way.

It makes me wince a little when I see writers about Early Modern Europe casually compare Italian states' responses to the spread of syphilis to the 20th-century AIDS crisis -- it's too pat, and it seems ahistorical in terms of how both conditions rose to cultural prominence -- but if you're interested in conceptual precursors to AIDS, you need to look at the post-1494 history of syphilis in Europe. If you're interested in how Early Modern people conceptualized venereal disease, how syphilis came to Europe in the first place, and why syphilis came to Europe when it did, I can give you recs for reading.