Colonizing a new star, question about virus/bacterial transfers

So, part of this is definitely not going to be GQ as it’s highly speculative, but the actual question I think falls into the GQ forum. Mods, feel free to move if you disagree.

Ok, so let’s say in the future, we have the ability to create a colonization ship to go to another star. We have the ability to create artificial wombs, to freeze embryos from necessary species we want to take with us (I realize we already have this), and have them come to term in the artificial wombs. We can do the same for humans as well.

The ship will need a crew, but it can be fairly small…let’s say 50-100 max, mixed couples. The trip will take 100 years, most of the crew is younger…maybe 20-40. So, obviously, they won’t survive the trip, not unless our life extension tech works a lot better than today.

Ok, so the GQ question is if they screened the crew (and the embryos, both human and whatever other species we take with us), could they colonize the new planet without a lot of the diseases that happen today. No flu, no rhinovirus, no ebola, no covid, etc, etc…basically, no harmful viruses? I’m fairly sure bacteria will be a whole other thing (though, thoughts on this would also be appreciated), but could this theoretical new colony, assuming they never have outside contact, be pretty much virus-free wrt some of the really bad viruses out there today? Or would this still be an issue going forward? I guess as a second question…COULD they even do this? Is it even possible?

I don’t see why not. But new ones would arise spontaneously. Probably not during the journey, not enough people or enough time, but in the eons to follow, sure. Viruses in particular seem to amount to random noise in the DNA replication process. Bacteria are native to our gut and that of other animals and given enough time, mutations would give rise to pathogenic ones.

I was going to post a scenario as a thread but I think I can do it here without hijacking because it is along the same lines because I think the main issue would be bacteria, viruses or other bad buggies.

You are orbiting a new planet. You know that the atmosphere is breathable gas and close enough to 14.7 psi for humans and the temperature is between 50 and 70 degrees Fahrenheit. Using current technology how would you determine if it is safe to explore the planet with no protection from the environment. Both for us and the new planet’s life forms

Viruses can infect embryos, and they can remain viable after freezing, so it seems likely that you’d carry along some number of viruses in the human and animal embryos on the ship.

That’s kind of what I figured. They would develop, over time, new ones. But they would leave the old ones behind, or at least most of them. Bacteria of course are a whole other matter. I was watching a really bad sci-fi movie about a colonization ship with a bunch of kids put on, and since the movie was really painful to watch I was wondering about the virus thing instead. Thanks for the answer!

My WAG is you’d send down a team that would initially be isolated (as isolated as you could make them) to get samples and run tests. Eventually, assuming you aren’t finding anything, you’d ask for volunteers to test it out, keeping the bulk of the crew in orbit and isolated. Eventually, assuming nothing bad happens to the team, you’d determine if it was ok to bring everyone down, though how long you’d want to test to be sure is certainly something I have no idea about. I guess a really long-term issue might slip through the cracks, but that seems like the best way to use current technology and methods to do what you are asking.

Well, there has to be a way to test and screen embryos for viruses, or harvest and prepare them in a clean environment before freezing…or, at least that would be my assumption. Since you could screen everything you plan to send, my thought was the actual crew would be the hard part, even using a rigorous quarantine methodology and a lot of time.

Add the condition of rigorous genetics screening for things like endogenous retroviruses. You’ll want to screen for known deleterious genetic variants anyway. You’re not going to be able to remove all these things, but you’ll want to limit the risk as much as possible. And really, any interplanetary colonization with limited diversity really needs practical genetic engineering to be survivable in an unknown environment.

Note, you’d want to include non-pathogenic bacteria and viruses with your colony ship. Multicellular organisms have symbiotic relationships with many of them.

I think animal testing would be part of the process, too. Can a plate of e. coli survive? How about a vial of fruit flies? And work your way up to mice, rats, pigs, or whatever you have around. Mixed in there could be human tissue samples. (Perhaps Henrietta Lacks will be the first one to go unprotected on an oxygen planet.) Do the human tissue and the animals survive?

That all seems doable with our current technology.

I’m assuming basic stuff like detecting radiation, poison gas, heavy metals, and such that we can detect easily right now is already done, and the place is clear of those things.

So, in theory we could eliminate all transmissible pathogenic viruses, bacteria, and (although you don’t specifically ask about it) fungi. Some have suggested that viruses would spontaneously emerge from cellular activity but in fact the emergence of novel viruses de novo has never been directly observed and is a topic of much debate in the evolutionary virology community; there is a theory of emergency from genetic operations (the so-called “vagrancy hypothesis”) that has loose RNA or fragments of DNA spontaneously joining with various intracellular mechanisms to become a free-floating virion capable of entering other cells and replicating, which is marginally plausible in certain types of prokaryotic-infecting bacteriophages but in general makes about as much sense as a car self-assembling from a junkyard. Although it is very difficult to estimate the evolutionary age of a virus because of the lack of uniformity in viral mutation rates, most pathogenic viruses appear to have very ancient origins. Neogenesis of novel bacteria or fungi are, of course, so unlikely as to be essentially impossible.

However, we do have a large amount of bacterial material in our bodies that is actually vital for various functions (e.g. the ‘gut microbiime’) and although no specific virus has been identified as being beneficial or necessary there is a suspicion that beneficial viruses may also play an important part in regulatory functions. How this would be transferred to in vitro grown embryos absent of mature carriers is unclear and may represent a significant hurdle if sources of beneficial live bacteria and active viruses cannot be transported and applied, and even if they are how the lack of exchange with the ‘normal’ terrestrial microbiome would affect things like immune system development. And this doesn’t just apply to going to hypothetical interstellar colonization, but even to the somewhat more plausible settlement of humans on other planets or habitats within our solar system where only a limited simulacrum of terrestrial conditions can be maintained. It has been suggested that some of the issues experienced by astronauts are a result of the impact on their personal microbiomes in a low gravity or freefall environment that may not be amenable to the normal exercises applied to tolerate musculoskeletal degradation.

So you could obviously sample the physical environment and analyze for known toxins or organic substances that might interfere with things like hormone regulation or neurotransmitters, and of course organometallic substances that would pose a risk. It is likely to the point of certainty that no native ‘virus-like mechanisms’ could infect human or animal cells and reproduce because they simply would not have compatible proteins or genetic sequences with terrestrial life even if they used nucleic acids to encode information, although it is certainly possible that they could provoke a histamine or other immune response as foreign material. Native ‘bacteria’ could potentially feed on basic elements or simple molecules like basic starches and maybe simple lipids that are likely to be universal energy storage among carbon-based life, but almost certainly would not be able to break down complex proteins or lipoprotein structures. Anything fungi-like could potentially infest a human organism and utilize nutrients such as water or minerals, again provoking immune response or just doing physical damage by displacing body structures, just like ‘foot fungus’ causes the soles of the feet to crack and peel.

All of this could be detected using standard methods of microbiological field and laboratory analysis, e.g. visual and SEM microscopy, X-ray crystallography, gas chromatography & mass spectrometry analysis, et cetera, but getting a coherent and complete assay of any potential threats would be the work of tens or hundreds of thousands of work-hours of field collection and analysis, even with automation just because any global biosphere would presumably be essentially as diverse as our own. It certainly wouldn’t be like Star Trek where they just do a “scan” with “life sensors” and declare an entire planet to be “safe”. Really, the only way to affirm safety would be to expose actual people to it (after a preliminary assay, of course) and see how they respond. If they explode in a cloud of self-replicating nanoids or turn into frenetic tentacle monsters, move on to another planet because this one is no good.


I’ve heard that for some common viruses like the various cold viruses, most people are carrying trace amounts of the virus at most times, and it’s just when the level gets too high that we feel sick. If that’s the case, then it would be extremely difficult to screen out those viruses.

I think that’s particularly true of the chicken pox virus; people typically get chicken pox as children and on recovery, the virus goes into hiding, only to re-emerge later as shingles.

I suspect that interstellar (and even interplanetary) colonists will need to have specially tailored microbiomes inside their bodies. It would be nice to think that this microbiota could be designed to avoid any possible evolution into pathogens, but it seems unlikely that such evolution could be made impossible, unless the microbiome were completely redesigned.

If a population of colonists was successfully isolated from any pathogens, this would make them vulnerable to infection by visitors - perhaps this would be a problem even between Earth and future colonies on Mars or the Moon, or between Earth and any successful large-scale space habitats. There are lots of problems to be solved concerning closed ecological life-support systems, and cross-infection is one of the problems that must be addressed before colonisation is practical.

Are there tests that can determine these trace amounts? If so, that could be part of the screening process for the crew I suppose, at least for the worst viruses. I would guess it would be easier for the embryos (human and non-human), as they could be processed in a lab before freezing.

You probably could test for them, but that’s only part of the problem. If you test and find that 90% of your prospective colonists are carrying Cold Virus Strain A, what then? And then what about strains B, C, D, and Z?

You could probably keep out HIV and HPV, and might even be able to keep out the likes of herpes (though an anti-herpes selection process would probably have a lot of other secondary effects, for good or ill). And anything we have effective vaccines for shouldn’t be a problem, since presumably anti-vaxer types should be heavily underrepresented among the colonists. But common colds? Good luck with that.

I heard a radio program that mentioned that one treatment that assisted longevity in mice was a fecal transplant. (The researcher also discussed doing fecal transplants for mice - for them, force them to drink it…) The point they made was that the gut flora play some interesting roles in how animals efficiently regulate some body processes. Also, I presume not just humans but a most other animals pick up gut flora from the environment as time goes on, so that needs to be part of the process of raising animals from embryo.

(Brings to mind the lunchroom conversation I heard long ago between to new mothers recently returned to work, about the progression of their babies’ diaper contents.)

Not to mention the need for a full ecosystem - flowers need bees, that sort of thing. Australia when settlers first brought cows, suffered from the lack of indigenous dung beetles. OTOH, rabbits did not suffer from a lack of local predators. (And google YouTube mouse plagues in Australia) Start bringing all this sort of stuff from earth and guaranteed there are some undesirable microbes in the mix no matter how hard you try.

But then - if you bring a few, say, covid virus particles along with the beehive, would it survive long enough to actually infect someone?

But any planet with sufficient partial pressure of oxygen already has a biome (which I presume the OP is asking about). I agree, the likelihood of a real disease making the jump is pretty rare - for every bat-related Coronavirus there are thousands of diseases which don’t adapt, and that’s between life forms far more similar than two different planets. The problem is - as mentioned - the risk of something more mundane. What if a local fungus really likes the warm moist lining of our lungs? Or eyeballs? What if local insects find us chewably delicious? (I think it was Asimov who had a short story where colonists mysteriously die after a few months - eventually someone notices that the cadmium levels are high, and that creates a lethal dose- not noticed because cadmium has not been used on Earth for centuries by then.)

I’m thinking there would have to be some sort of test strip/panel set out to see what grows on it. Until then, people would land with robotic landers with mechanical arms and never leave that ship, which would be thoroughly irradiated in space on return before hooking back up with the mother ship. Perhaps step 2 would be to grow some chimps and put them out to see what happens, using the same robot landers - then dissect them to try and see what happened. Then human volunteers.

My alternate plan would be - take no chances - use the fusion drive of the starship to irradiate the planet so nothing is left alive, then seed it with earth stock.

In the movies, that’s what the bad aliens do when they come here.

“Scan for life forms” is a well known 24th century euphemism for “beam down a bunch of red shirts”

Figures. :slight_smile: We finally get an extra-solar colony and we STILL have the common cold! Well, that’s kind of what I figured.

Well of course. It’s a choice - either put up with whatever the alternate ecology can throw at you, or start fresh. It depends what level of radiation is needed. The theory is that radiation from a nearby supernova could basically destroy all life on earth. I wonder if that includes life deep in the oceans or deep in caves. All it takes is a few single cell organisms to survive, and presumably evolution begins anew.

As far as I can see, there’s ultimately no choice other than - “Looks ok, I need a few volunteers to take off their helmets…”. IIRC King Louis tested the Montgolfiers’ balloon flight by promising a convict his freedom if he took the test flight. Maybe each starship needs a contingent of Australians.

But as for screening for imported bacteria and viruses - we probably don’t have the tech to screen every cubic micrometer of imported material for detrimental bacteria or viruses; nor the tech to eliminate them. As mentioned, people once infected harbor chicken pox bacteria that re-occurs as shingles. Not to mention the same effect from HPV, herpes, syphilis, etc. If your tech system sees a bacteria, for example how does it tell normal gut bacteria from deadly e coli? Yo can’t do a gene sequence on everything without also killing them all.

Then there’s the theory that high rates of allergies in children nowadays are a side effect of clean freak parents, so the child is never exposed to bacteria and diseases that exercise the immune system - instead it goes after things that are not toxins. Would a world without colds mean a world without peanut butter?

My take on the OP’s question is that you can screen as well as you can, but some compromises may be needed, some things will slip by - and by then, keep an encyclopedia of medical treatments and how to make vaccines. …oh, and don’t take people on the ship if they refuse to be vaccinated.