Throughout history, slavery has been plagued with the infection, disease, and other immunological disorders arising from a particular people group being forcibly transported to a working environment in which their immune systems have not had time to adapt.

One example would be the sicknesses that beset African-Americans brought to the Caribbean by British and French slavers during the 17th century. Although nearly half of all slave deaths may have occurred before the slaves even reached the Americas, even after they arrived in the Caribbean life-expectancy was only 20 more years. This was due to their inability to adapt to diseases and illnesses present in Jamaica and other such places, while under the strain of incredibly hard forced labor (though certain slavers made point of not giving new slaves the hardest jobs, so as to protect their investment).

So my scenario is this: aliens have visited Earth, and taken humans back to their homeworld with them as slaves. Assuming the aliens are humanoid and the planet is Earth-like, my assumption is that a situation similar to that of African-American slaves in the Caribbean might play out.

But for the purposes of my story, this is not the situation I want to play out. I'm wondering, instead, if there's any way this could all unfold in reverse, that is, is there any way that, instead of the humans becoming infected with various diseases present on the alien planet that they've not had time to adapt to, could they instead bring an Earth disease with them, one that they are immune to, but the aliens are not? In other words, is there any way that humans, brought as slaves by aliens to the alien homeworld, could inflict disease and other immunological failures on the aliens, and not the other way around, as has usually been the case throughout the history of human enslavement of other humans?


4 Answers 4



Our biologies are likely to be so radically different that in their own environments each species has home field advantage. On Earth our microbes thrive, on their world, their microbes thrive.

Even if our microbes could pose a threat, there is no way that that would be slaves would not be quarantined/studied first. If some microbe on/in us posed a threat or vice versa, they would know about it and enact a measure to deal with it. We even practiced this, Apollo Astronauts were quarantined upon their return from the moon for example just in case.

Unless... What follows is not impossible, just extraordinarily unlikely

Because our biologies are so different it is possible that they may misidentify a pathogen. I'm not saying they are going to miss a flu virus or an E-coli bacterium because if they can travel the stars they can pick those out. They just might miss a Prion; which can be thought of as a super simple virus though that's not quite right more of a misfolded protein. It's a (single?) protein that when introduced to the body behaves like an illness. Here is how they may miss it: a Prion may be indistinguishable from any other protein in the body because the only flaw is it is folded wrong. The alien scientist may assume that it is part of our biology or miss it all together because it's a single molecule.

Now, our biologies are almost certain to be radically different, but the building blocks may not be. Ammino acids have been found in space so it's not unreasonable to think they may share many similar molecules. Which means that Prion they missed could be compatible with something on their home world and * just might* be the source of illness. Even then, probably not.

  • $\begingroup$ Alright, @Joe Kissling, I'm going to be stubborn and look for a way my scenario might still work (however far-fetched it might be), but I appreciate the realistic answer. $\endgroup$ Apr 6, 2017 at 23:00
  • $\begingroup$ @C.S.Wright Please hold $\endgroup$ Apr 6, 2017 at 23:04
  • $\begingroup$ I don't know what that means. Are you asking me to put the question on hold? $\endgroup$ Apr 6, 2017 at 23:06
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    $\begingroup$ @C.S.Wright I just read an article this morning about how scientists have evidence that a simple harmless reovirus in infants is responsible for triggering the genetic celiac immune disease that they have the genes for. So it could be that your aliens research the human slave stock and say that certain human virus/pathogens/bacteria are harmless/benign and then later it interacts with dormant alien genes setting off unexpected chain reactions. I was going to write my own answer but Joe has already covered most of what I was going to write. $\endgroup$ Apr 7, 2017 at 7:45
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    $\begingroup$ Thanks, @EveryBitHelps. Even if someone beat you to the answer, every bit helps. $\endgroup$ Apr 7, 2017 at 19:01

This should really be addressed on two different levels.

First, can "really alien" creatures have a biology/DNA which is so similar to ours that transmission in either direction is possible? This seems wildly improbable. However, improbable is not exactly the same as impossible, and if the aliens are willing to go the effort of bringing back slaves, it seems likely that the alien biosphere is, in fact, compatible with us. If it weren't, humans would not be able to eat the food produced on the alien world, and it seems a stretch to think that aliens would so prize human slaves that they would maintain a constant transfer of food from Earth. Well, OK, a good imagination provides various possibilities, such as our pheromones being intense euphorics (or whatever the alien equivalent of euphoria is). Or, perhaps, our vocal structure is perceived as extraordinarily pleasing, so humans are kept as the equivalent of songbirds. The list goes on, but it does all seem rather unlikely.

Within our own biosphere, the vast majority of diseases are species- or genus- specific, so we (people) don't catch diseases from animals. Exceptions such as toxoplasmosis (from cats), influenza (from birds), or rabies (from any number of mammals) do exist, but they are clearly exceptions. So sharing diseases with something even more foreign than these examples seems extraordinarily unlikely.

If you're willing to overlook this, then there is absolutely no reason why disease transmission should be one way. While you cite the experience of African slaves in the Caribbean, the example you give is amazingly one-sided. Europeans sent to West Africa died in droves due to local diseases (primarily malaria and yellow fever, but there were any others such as dengue fever and sleeping sickness) which the locals seem to have had some immunity to. In the 1800's Sierra Leone was called the White Man's Grave. Mortality rates for newcomers often ran to 50% or more in a few months.

Finally, consider the strong (but not conclusive) case that has been made for the New World as the source of syphilis, and note especially that the first outbreaks were far more deadly than the current version.

  • $\begingroup$ I was reading an article (well, i really just read the blurb so cant say much more) about how bacteria that causes human disease have been found in orca blowholes. That is quite a wide species gap. Then there is the whole koala virus saga (similar to AIDS) which scientists believe they acquired recently from an exogenous source (how recently I haven't figured out yet). $\endgroup$ Apr 7, 2017 at 7:39
  • $\begingroup$ @WhatRoughBeast, I'm operating under the assumption that since we haven't yet discovered extraterrestrial life, it's possible that the conditions required for life are highly specific, and would thus produce organisms and conditions similar to those of Earth should they occur on another planet (thus my assumption that's it's possible in the first place for humans to infect aliens or vice versa). And good point about Europeans becoming infected in Africa, but it still leaves me with the dilemma of reversing the situation. I need the foreign humans to be the ones who infect, not become infected. $\endgroup$ Apr 7, 2017 at 18:59
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    $\begingroup$ @C.S.Wright - An obvious approach is to keep in mind that most diseases are not fatal. So (purely by luck) you could have the alien diseases causing no major harm to humans, but human diseases causing death and disfigurement to the aliens. In simple terms, we get alien colds, and they get the Spanish flu. Since the two species have not had remotely the same disease suites, and their genetics are different, there is no way to tell how each group would react to the other. $\endgroup$ Apr 8, 2017 at 0:54

As Joe says, an alien environment is likely cleaner than ours.

Viruses are definitely out unless that alien race seeded the Earth with their own DNA. A virus trying to use alien DNA (in this case, we're the aliens) to reproduce is like using a key to open a car tire.

Bacteria organisms may work. If it can consume the raw materials of our cells it can eat us. If it is chemically different enough, our bodies may not know they are under attack. Think a staph infection that does not cause redness, swelling, or fever; you just start having open wounds that appear and grow on your skin (or internally).

You may also encounter creatures like The Blob. It might be an alien disease or kudzu type creature that it kept in check in its normal environment.

Plants or fungi could be bad. Think of something too small to see until it multiplies that grows roots into you just to get at the water in your cells and veins (and maybe a few other common elements). With fungi, all you visibly see are the reproductive organs. By the time you see anything, it is really entrenched.

  • $\begingroup$ let me clarify; I'm asking if there's any way that humanity's alien captors might be infected by humans, not the other way around. $\endgroup$ Apr 6, 2017 at 23:29
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    $\begingroup$ @C.S.Wright Then turn it around. If they have wet skins, fungus would grow there. If they have transparent skin, algae might grow in their blood. $\endgroup$
    – ShadoCat
    Apr 6, 2017 at 23:43

Chances are more likely that neither races diseases would affect the other. And slavery in many regions of earth was between simmilar populations unlike America's slavery.

Perhaps a human parasite might take a liking to aliens for some reason but be fatal to them? Assuming they don't sterilise the humans to the skin (and even then there are insects and worms that can be internal). Something as simple perhaps as worms could be totally poisonous to aliens while a fixable nuisance to humans.


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