The Great Plague is known as one of the worst pandemics in human history as it killed between 75 and 200 million people from 1347 to 1351 (according to wikipedia).

I would like to know if AIDS had erupted during the same period of time, would it have been more or less as deadly?

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    $\begingroup$ I'd say that AIDS in medieval times would have provided a lot of moral ammo to the Church... at least, until the first priests started dying as well. $\endgroup$
    – Rekesoft
    Commented Jul 20, 2018 at 10:23
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    $\begingroup$ Some peole argue we don't have a time machine to see how thing are in medieval times. They are wrong. We already have a good time machine and it's called airplane, it's just a matter of setting the correct "time coordinates". Go to a remote and very poor third world corner of the world and you are effective in the medieval times regarding religion, social dynamics and organization, etc. Sometimes there are firearms but putting those things aside it's all-in-all a medieval time, same overlord/peasant/land stuff. Just search how things are happenign here and you will have your answers $\endgroup$
    – jean
    Commented Jul 20, 2018 at 11:17
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    $\begingroup$ We're still going to blame the cats. Friggin cats giving people AIDS... $\endgroup$
    – Machavity
    Commented Jul 20, 2018 at 12:08
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    $\begingroup$ @jean That is overly simplified. I've traveled to remote corners of third world countries personally. I also lived in rural India for years. Even in the most desloate corners of countries much worse off than India, where empoverished people live, you will find the occasional cell phone, solar panel, soap, medicines, motor vehicle, TV, book filled with medical knowledge, visiting doctor, antibiotics, condoms, etc. to state that one could travel to a corner of a third world country to learn about medieval times is rather arrogant and over simplified. $\endgroup$
    – Fiksdal
    Commented Jul 20, 2018 at 13:22
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    $\begingroup$ @Revetahw I disagree, I has lived in such places and there's a lot of parallel when things go for social relations (given regional cultural parcticularities off course) but some gadgets don't have a big impact, in special when not everyone can afford them or theres not eletricy to start. To me the bigger "modernity" impact is by far medicine but I has visited such places without eletricity, medicine, potable water and is those places I was speaking about $\endgroup$
    – jean
    Commented Jul 20, 2018 at 13:42

6 Answers 6


AIDS is a sexually transmitted disease, and we have the chance of another STD which appeared out of nowhere around those times (actually about a century later): syphilis.

When it was imported from the Americas, it quickly spread across Europe, limited only by its own feature of disfiguring the persons it infected (which is actually thought to have made it evolve less virulent, to allow the victim to still be attractive enough to have intercourses). Mind that religious objections to a multi-partner-oriented sexual life didn't succeed in stopping the propagation.

In the case of AIDS we would have then sexual transmission and lack of countermeasure (silk or gut condoms used in those times are ineffective against the virus), helping the disease to spread.

Also don't forget that the common remedy for any illness was to slit open a blood vessel (usually near the elbow) and drain about half a liter of blood. The instrument used for cutting was not cleaned much and definitely not sanitized between patients. The same applies to tooth pulling, amputations and all the merry services of barber-surgeons. When you think about it, a single traveling barber-surgeon could have wiped out entire areas in a few years time. (credit at YElm for the hint)

The slow onset of the disease would have been also favoring its propagation, and the constant usage of the immune system in those times would have lead to quick deaths as soon as the deficit would have arise. Imagine an infected soldier in the latent phase, visiting various brothels across Europe before being killed by a small infection following a war wound.

Finally, considering that it doesn't show any major symptom (like fever), it would have not even raised any attempt to stop it (like isolating the sick). All in all, it would have been more deadly than the black plague.

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    $\begingroup$ It's a myth that syphillis was introduced through the Columbian exchange. It was endemic to Europe from prehistoric times, usually referred to as 'leprosy' (and indeed, tertiary syphillis is difficult to distinguish from true leprosy in many ways). Trick is, it's harder to spread syphillis than plague, since the bacterium can not be spread through casual contact, coughing, sneezing, or contact with contaminated surfaces. It's the same with HIV. In neither case would the STI have been as virulent as the Great Death. $\endgroup$ Commented Jul 20, 2018 at 15:38
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    $\begingroup$ Also, the long incubation time and lack of any specific symptoms would mean they woudln't even know it existed. They might realize that people are dying more often of minor wounds than it was a generation ago, and later it would be entering the realms of legends of ancient heroes being stronger and more resistant. $\endgroup$
    – vsz
    Commented Jul 20, 2018 at 16:47
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    $\begingroup$ @jkd, only if you assume they started to be sexually active at around 20. And don't forget mother transmitted infection. $\endgroup$
    – L.Dutch
    Commented Jul 20, 2018 at 17:37
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    $\begingroup$ You've forgotten that AIDS virus survives only in fresh blood, travelling blood-barber would cause more hepatitis... $\endgroup$
    – user2061
    Commented Jul 21, 2018 at 12:41
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    $\begingroup$ @jkd : average lifespan of 40 doesn't mean they dropped dead due to old age at 40. The high child mortality is the most important factor. If someone survived into his twenties, he had a good chance of reaching 70 or more. $\endgroup$
    – vsz
    Commented Jul 21, 2018 at 23:00

The plague was worse... a lot worse...

The worst epidemic of AIDS we know of or have known of is the South African plague, which has as its highest infection rate only an excess of 15% (source). Assuming 100% lethality, that's only a 15%+ infection rate in small parts of Africa. The Black Death is estimated to have killed 30–60% of Europe's total population.

There is no evidence at all that AIDS can spread as quickly as the Bubonic Plague. On the contrary, the evidence demonstrates that it spreads much, much slower.

AIDS is likely more lethal than the Black Death, but it's only transmitted sexually and it has a much longer incubation time. 10 years compared to the Bubonic Plague's 2-6 DAYS. The average lifespan in 1300 was 31 years. This means the plague could affect ANYBODY during their 31 year lifespan but could only affect an individual for about 5 years assuming they became sexually active at age 15. (This assumes they weren't born with the disease.)

To achieve the kill rate of the Plague, the average person would need to be sleeping around so much that you could easily connect the average person to any other average person through sexual activity in the same way we play Six Degrees to Kevin Bacon.

While I have little doubt the average person is permissive in their behavior, I have a substantial problem believing the average person is that permissive. Far more common and easier to contract sexual diseases existed in the Medieval ages and yet had no where near the infection rate necessary to judge AIDS more deadly to the population of that time.

In the end, the issue is not the lethality of the disease or how hard it is to detect, but the ease with which it can be contracted. The Plague was the proverbial million times easier to contrat than AIDS ever was or is. Conclusion: the plague was worse... a lot worse...

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    $\begingroup$ Its symptoms however where ten times more obvious than AIDS will ever be. Its estimated HIV could have gone unnoticed by researcher for over a century. So AIDS would simply go global just very slow killing people After they had already given birth and raised children. $\endgroup$
    – Mellester
    Commented Jul 21, 2018 at 19:32
  • $\begingroup$ @Mellester, noticability is irrelevant. Only communicability is relevant. The average lifespan in 1300 was 31 years. A disease MUST spread quickly to be a plague. Stealth only means blocks of people (not Plaque-level at all) will suddenly die for unknown reasons every 2-3 generations, but that's it. You'd never lose 2/3 of your population to it in one go. $\endgroup$
    – JBH
    Commented Jul 21, 2018 at 19:40
  • $\begingroup$ Yeah but the question is which one is more deadly. Not which one is quicker in killing more in a choosen time frame @JBH $\endgroup$
    – Mellester
    Commented Jul 21, 2018 at 19:47
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    $\begingroup$ The "average lifespan" from birth was 31, but from 1200-1300 in England, once someone hit 21 they had an extra 43 years or so of life expectancy (due to the black death, from 1300-1400 this was reduced to an extra 24 years) books.google.com/… $\endgroup$ Commented Jul 22, 2018 at 0:19
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    $\begingroup$ @LorenPechtel In the long run, we all die. How many people of the medieval ages is still alive today? Apart from some politicians, they're all long dead. A plague is a disease capable to wipe out a lot of people from the same generation. If it kills a lot of people through several centuries... well, everybody dies one day. $\endgroup$
    – Rekesoft
    Commented Jul 23, 2018 at 6:56

Bubonic plague

Bubonic plague is an infection of the lymphatic system, usually resulting from the bite of an infected flea, Xenopsylla cheopis (the rat flea). So it can carry on after an area is completely dead, and, more importantly, it can occur without any infected people around so long as there are rats carrying the infected fleas.

Medieval Europe was a very messy place, the perfect breeding ground for rats, and the fleas went with them.

The infection takes three–five days to incubate in people before they fall ill, and another three–five days before, in 80 per cent of the cases, the victims die. Thus, from the introduction of plague contagion among rats in a human community it takes, on average, twenty-three days before the first person dies.


You can get or transmit HIV only through specific activities. Most commonly, people get or transmit HIV through sexual behaviors and needle or syringe use.

Only certain body fluids—blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk—from a person who has HIV can transmit HIV. These fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into the bloodstream (from a needle or syringe) for transmission to occur. Mucous membranes are found inside the rectum, vagina, penis, and mouth.

This means that you basically have to be very friendly with someone that has HIV or use syringes that have not been cleaned correctly after use by someone with HIV.

Left without treatment, the majority of people infected with HIV will develop signs of HIV-related illness within 5–10 years, although this can be shorter. The time between acquiring HIV and an AIDS diagnosis is usually between 10–15 years, but sometimes longer.


In the medieval times there were no syringes as we know them today, and the deeply religious time restricted widespread... "extra curricular activities" so HIV would not have been able to spread even as fast as it has in modern times, let alone medieval.


While the black death is far, far more rapid, it did manage to burn itself out, however HIV/AIDS would have taken a lot longer to be noticed and for people to die from it, but would most likely still have burned out due to the discretionary customs of the time.

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    $\begingroup$ not so sure about the spread (see my answer) $\endgroup$
    – L.Dutch
    Commented Jul 20, 2018 at 9:33
  • $\begingroup$ @L.Dutch Alas my friend... i didn;t even consider brothels... i shall try and remember to place my head into the gutter more often. Fair point well made $\endgroup$ Commented Jul 20, 2018 at 9:53
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    $\begingroup$ "The deeply religious time restricted widespread extra curricular activities": oh really? You may want to brush up on The Canterbury Tales (from England), The Decameron (from Italy), Gargantua (from France), and so on. "Extracurricular activities" were at as commonplace as today. I'm not saying that there were no monks who took their vows seriously, but most rich men and even several Popes had well-known concubines; for a taste of truly medieval "deep religiousity" look up the Saeculum Obscurum, also known as the age of Pornocracy. $\endgroup$
    – AlexP
    Commented Jul 20, 2018 at 10:43
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    $\begingroup$ As @AlexP points out this answer is based on misconceptions about the social norms of the day. Short version : shouldn't doesn't equate to didn't. Also HIV/AIDs attacks the immune system so it would have a devastating effect at a time when no technology existed to compensate. In addition to this people dealing with everyday (minor) wounds, births and so on would have been exposed to HIV and other diseases a great deal more than in a modern context. No sewers, for example, and a complete lack of understanding of hygiene makes a disease that affects the immune system extremely dangerous. $\endgroup$ Commented Jul 20, 2018 at 11:12
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    $\begingroup$ “and the deeply religious time restricted widespread… ‘extra curricular activities’” — oh honey. $\endgroup$ Commented Jul 20, 2018 at 16:08

AIDS would not have been great. The plague was worse. Much worse.

There are people who simply don't get HIV https://en.wikipedia.org/wiki/Innate_resistance_to_HIV

And people of European descent have the highest occurrence. https://www.wired.com/2005/01/genetic-hiv-resistance-deciphered/

It's theorized by some that the survivors of the bubonic plague passed along a resistance that also helps against HIV.

Also, the really destructive effects that make a huge pandemic worse are the ripple effects of the sickness. If a substantial percentage of your working adults all get sick and die within a few weeks of each other - and parts of Europe supposedly suffered 70% death rates - society falls apart. Crops don't get tended. Livestock break loose or starve. Taxes aren't paid, or collected. Towns are abandoned. Even places without plague outbreaks suffer from starvation or secondary disease outbreaks. People get scared, trade fails. It's bad.

Even if people were dying of AIDs, it would be gradual. Society would survive fine. Of course, it wouldn't burn itself out either... so if you mean in the fullness of time, over centuries - then yeah, AIDS would end up killing more, but it would have less of an impact anyways. Medieval people dealt with mortality all the time, it was the suddenness of the plague wiping out so many at once that was such a debilitating thing.


Aids would have behaved more or less exactly like syphillis did.

AIDS is a sexually transmitted disease, and we have the chance of another STD which appeared out of nowhere around those times (actually about a century later): syphilis.

When it was imported from the Americas, it quickly spread across Europe, > limited only by its own feature of disfiguring the persons it infected (which is actually thought to have made it evolve less virulent, to allow the victim to still be attractive enough to have intercourses). Mind that religious objections to a multi-partner-oriented sexual life didn't succeed in stopping the propagation.

(out of other answer)

Primärstadium, Lues I


Auch unbehandelt heilen die Geschwüre von selbst nach ca. 4–6 Wochen ab, weshalb die Erkrankung oft ignoriert oder nicht erkannt wird.


Sekundärstadium, Lues II

Acht bis neun Wochen nach der Ansteckung


Alle Hauterscheinungen (Syphilide) heilen nach ungefähr vier Monaten ab, so dass manche Patienten von ihrer Infektion wenig bemerken.

Unbehandelt kommen sie innerhalb verschiedener Zeitabstände wieder. (und heilen wieder ab...)

Bei vielen Erkrankten kann die Syphilis in der folgenden Latenzzeit zu einem Stillstand kommen; die Erreger sind jedoch noch im Körper des Betroffenen. So kann sich nach Monaten oder Jahren eine Spätsyphilis entwickeln. Der Infizierte ist ansteckend, auch wenn diese Gefahr sinkt, je länger der Patient beschwerdefrei bleibt.


Tertiärstadium, Lues III

Drei bis fünf Jahre später



In english: The first stage of syphilis you often don't recognize as syphilis at all or ignore because the few ugly things on your skin disappear 4-6 weeks after infection.

The stage when you get ugly follows after 8-9 weeks after infection. A few months after you got ugly, you get beautiful again. A few months later, you get ugly again. (and this repeats)

Syphilis may stop totally (or for just some months or years) at that stage, so you don't feel and look sick anymore but you are still infectious.

But, after 3-5 years after infection, the third stage of syphilis starts (thats when you get permanently ugly and may die)

So, like in the aids case, you have some people who look healthy although they are infected and spread the disease for years. (yes, syphilis makes more of its victims permanently ugly in shorter time, but therefore it's more infectious (it can even be transmitted through food) (just think about medieval taverns)

so I think although there are differences

( Syphilis - faster in making you ugly (in average) (although you can stay beautiful for years and infect your whole town) - much more infectious


HIV - slower in making you ugly (in average) (although you can get ugly and die from HIV quickly, too + it's not as slow as you think when untreated-see HIV behavior when untreated -> > 90% die after 2-15 years, ~ 80% die after 5 years and 10 years.) - much less infectious

The effects on a medieval world would be more or less the same. (I think the differences compensate themselves)

So I would compare the actual syphilis epidemic with the black death epidemic and assume that Aids would behave the same as syphilis did.

Since syphilis stayed in europe until the first world war, (history lessons) I think syphilis was worse than the black death epidemic you're talking about (70.000.000-200.000.000 deaths). (caused more deaths since it had much more time)

=> Aids would be worse than the black death epidemic you're talking about as well.

(If anyone argues that aids would kill you faster in a medieval world because you get an immune deficit, that's true, but syphilis would kill you faster as well if you get additional diseases.

  • $\begingroup$ Hello, KGM, and welcome to Worldbuilding.SE! Please take our tour and visit the help center to learn more about the way the site works. Have a nice day! $\endgroup$
    – Gryphon
    Commented Jul 20, 2018 at 17:05
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    $\begingroup$ Maybe just add the English Wikipedia page instead? $\endgroup$
    – Cain
    Commented Jul 20, 2018 at 19:27
  • $\begingroup$ I am german native speaker, but if you want to, you can replace the quotes by english wiki ones or translate them. $\endgroup$
    – KGM
    Commented Jul 20, 2018 at 19:42

As others have mentioned, plague is way worst simply because it can spread quicker, has a much smaller incubation period of 1 to 7 days compared to HIV's incubation period of several years and is much more lethal in the short term.

This isn't even counting Pneumonic Plague, which would spread even faster through person to person since it's airborne and is 100% lethal in a day or two (even today bubonic plague can still be lethal even with treatment).


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