Description :

Even in the ⅩⅩth century, biological warfare was studying only existing diseases.
But recently we're able to modify viruses in order to cure genetic impairments. Would it be possible to use similar techniques to build the perfect weapon?

Requirements :

According to me, that weapon would need to have got one or several of the following characteristics :

  • Have a long-term nonprogressor: Most offensive diseases (such as the black death or the 1918 flu pandemic) that kill their host rapidly end up disappearing because they destruct their own contagious potential. That’s why the ideal disease never kills its host. Not showing any symptoms for years, while still being contagious, is the ideal outcome. It would also allow the virus to evolve and adapt itself to various natural defenses of its host (HIV is starting to do it).
  • Be a RNA based virus: In the event the researches around the disease are discovered, it’s important to prevent any curing methods to become successful. DNA based viruses are vulnerable to vaccines. Bacteria have their own viruses and are vulnerable to antibiotics.
  • Infects or attacks wild animals :
    In the event that the disease is uncovered and a treatment is found, having animals infected could prevent the disease from disappearing (smallpox would still exist if it wasn’t an human only disease).
    Ideally it should be animals which are difficult to eradicate such as flying insects. Unlike humans it doesn’t need to kill them, but just be able to infect them.
  • Have as many carriers as possible :
    HIV fits several categories required to be a biological weapon, however the requirement to have sex with someone you don’t know well, or use drugs stops it from being as successful as influenza which use aerial vectors. It’s still better to combine vectors (for example being aerial like influenza/Sars Cov2 and being able to infect through sexual relations as well).
  • Replicate common mammals proteins while being in the viral form: This should trigger massive auto immune reactions that would kill the host. Research on the root causes of auto‑immune diseases tend not be on infectious causes. Once the root cause is established, doubts might be spread in medical authorities of various countries due to that characteristic (resulting doctors trying to prevent contagion getting sued) (South Africa is the most well known example with AIDS). This should delay research results by several years: enough to kill most of the worldwide population.
    As the proteins would be common in various type of cells inside bodies, the symptoms are very broad. As it should be non detectable in half of the cases people surviving the first week would get wrongfully sent in mental hospitals (this idea come from the borreliosis though I agree it should be impossible to mix bacterial and viral genomes).

Every point above is a characteristic that already exists in today’s diseases. The issue is combining them (it’s easier to find the gene responsible for something rather than building something from scratch). But there’s more that could be done to get it “right”: the etymology of Epidemiology means something that is located somewhere. Having a spot of a particular disease is a red flag for an infectious root cause.
So it should be spread in various places of the world. The infected people traveling to those places needn't volunteer (simply pay some citizen at random the high price so they voluntarily move abroad)

What could lead to the creation of such weapon ?

Purpose :

This is definitely the wrong weapon if you want to win a war :

  • First, it will takes up to a decade to become effective. The war could have ended.
  • Second, you rarely fight against the whole world.
  • Third, in the case you win, it will end up collapsing your own state. There’s no target

However, if you are the perfect authoritarian regime with a NATO war against you, then it’s completely understandable to take revenge against the whole world when you’re about to be defeated by using what was created years before in the event you had to face that situation.

False limiting factors :

  • It’s impossible to kill everyone, a minority of peoples will survive :
    The weapon should still be very efficient. If only 10 million people survive, you’ll still get a perfect collapse as their wouldn’t be anymore states for centuries. At least, not in the organized modern way we actually know.
  • The biological weapons convention is soft. Much like the united nations convention against torture.
  • It’s impossible to build something that can end mankind because some characteristics are too hard to build…
    Wrong! Just add more contagious vectors to HIV and you’ll get something usable (HIV is starting to adapt to antiretroviral drugs). Maybe it would mutate back so it can infect monkeys because it would have got widespread among humans.

Real mitigations :

  • Large states have no reason to perform such research.
  • The technological requirement is too high for the states or armed groups/rebellions. Not to mention the funding requirement.
  • Whenever you support an evil state run project, you know things should generally be fine for you. Currently, you know what you create will kill you in a horrible death.
  • Nobody would dare to attack you if it’s get publicly known you have such weapon.

Final Question :

With all the conditions above : would it be realistic for such a weapon to be created in the next decade ?
For example, what about just adding more contagion vectors to HIV ?

  • 1
    $\begingroup$ Well, a so long post ,their should be language mistakes (except for capital letters). As I’m not a native English speaker, please edit the question instead of downvoting for such errors. $\endgroup$ Commented Aug 18, 2016 at 21:56
  • 1
    $\begingroup$ One of the hardest requirements here is the species cross over. It's not a hard leap to have an insect carry a disease from human to human, however to be able to infect the insect as well as the human is a different story, our biological make-up makes that very difficult. $\endgroup$
    – Twelfth
    Commented Aug 18, 2016 at 22:55
  • 3
    $\begingroup$ It's highly unlike nuclear weapons. Nuclear explosion is limited in size, limited in damage, and whilst powerful, it's also controllable. You can use them to threaten others because they know it's not a suicide for you to use them. $\endgroup$
    – Mołot
    Commented Aug 18, 2016 at 23:26
  • 4
    $\begingroup$ Can work with two diseases, one who spreed inoffensive at first, and a second who triggers the killing of the first ? $\endgroup$ Commented Aug 28, 2016 at 1:04
  • 2
    $\begingroup$ @Annonymus Forcing a virus to adapt by subjecting it to radiation would not make it better at doing anything apart from surviving radiation. No living thing has a simple sliding scale of "stronger" vs "weaker", there is always a trade-off between its different properties. The new virus may be more resistant to radiation, but it may also be less contagious, reproduce more slowly, or have any number of traits that keep it from being an effective weapon. $\endgroup$ Commented Nov 6, 2016 at 13:56

12 Answers 12


Thinking about all the needed conditions our hypothetical Bioweapon needs to fulfill, I came to a conclusion that such a virus would not spread too well or might be made and set free for world annihilation - Even H5N1 could not reach a pandemic level for it burned through hosts too fast and was detected too easily. Spanish Flu and COVID-19 did reach pandemic on their own because they are highly infectious, but they were/are not nearly deadly enough for this scenario - Spanish Flu in 1920 had an incubation time of about a fortnight and an estimated death toll of 20-50 million while the world population was 1.8 billion with the medicine of that time, and quarantine like in the case of American Samoa was a highly effective way to reduce the exposition to the virus.

The distance between human population centers and the huge variety of human genome makes it improbable that one virus could keep silent long enough to infect all the population of earth before the first breakout happens. If people start to die rapidly the various health centers react pretty fast to try to start an epidemic control and isolate areas as it happened in the case of H5N1 and Ebola in the last decades and recently with COVID-19. So the only way for a virus to spread globally and infect all would be one that is not considered a threat by everybody the moment it is noticed. Common cold, for example, does that every year, there are millions of variants, but few kill - which is why no epidemic control barriers are raised because of it.

COVID-19 did raise all the alarm flags as early as January 2020, but many states did try to rely on other countries reactions and lower levels of isolation until way too late, allowing the virus to spread to and then from multiple centers, which lead to the late-march 2020 actions of pretty much shutting down the public life in Europe on multi-national level and a huge amount of travel bans to slow infection rates and buy time for cure research. Meanwhile, in all countries, people panic and self-isolate, hoard basic needs and try to stay out of crowds where the virus might be. And global panic is against the requirements.

But how?!

So you have to eliminate the human factor of starting to panic if people start to die somewhere en masse and cut down connections to that land. To do this, the hypotetical virus would have to be either a retrovirus (like HIV) that can have years between infection and outbreak, or it has to be 'quite harmless'. The bioweapon you want however is far from quite harmless.

So, the only way the bioweapon could reach all population before being discovered by the illness or killing, and subsequently be isolated and/or eradicated would be to give it a long incubation time - which however only increases detection chance as it spreads for each day millions of blood samples are tested for various illnesses. If new, unidentified virii get detected in those, the isolation protocols are easily kicked in and research for a specific antibody is launched. Also, remember that human genetic variance and rule of large numbers will lead to at least one infected being studied that is at least resistant to the illness - which in turn could be the start for a working anybody! So, unintentional spread of a deadly disease with the demanded conditions is out. (Just like even making it!)

However, how about intentional, controlled spread?

Let's assume the virus might be added intentionly to food or medicine and then the rigged stuff is given out free or cheap to maximize reach all over the population. This plot is entirely different! In this case, the virus does avoid detection for a some time by the vector it is given: people assume governement given aids are checked and clean of such tricks. Thus it might manage to reach all continents before it has to go on alone because it was discovered.

Now, why pass out a deadly illness? That kind of stuff might be detected and thus isolated by the death count alone as shown above! If you want to stay under the radar, it would be wise not to kill the host but instead pass out something 'quite harmless' with more long term effects. Maybe render the victims infertile or heavily allergic to some usually harmless substance that people don't usually encounter.

I guess, something like a governement aided genetic manipulating virus could reach pandemic level within a few months to years, especially if the responsible parties manage to keep a thumb on the media and thus doom humanity to die out eventually. It doesn't even need to be an airborne virus, or able to pass from human to human at all. Just infecting enough people to bring human beings in larger areas below the 50/500 threshold* is enough. Something like this was the plot of a Stargate episode by the way. So I rule:

Only if parties actively spread the virus in a way that disguises its nature, pandemy can be achieved, and even then the virus can't be of a deadly, slow kind but would need to target survivability as a whole.

*The 50/500 Rule is a concept from 30 years ago, telling these are the numbers for minimum viable population size. Nowadays the numbers 50 for short term and 500 for longer term survival are thought too small: many biologists say, that to ensure genetic diversity about 2000 or even 10000 genetically diverse individuals are needed. Read more here and here

  • 1
    $\begingroup$ So you have to eleminate the human factor of starting to panic if people start to die somewhere en masse and cut down connections to that land Yes, that’s why I listed various place of the world as the first infected persons. aids was a good case because it remains 60 years undetected. $\endgroup$ Commented Aug 21, 2016 at 20:11
  • $\begingroup$ As I explained in my question. I’m thinking about something asymptomatic during years, which then kill victim. $\endgroup$ Commented Feb 5, 2018 at 1:20
  • $\begingroup$ As explained above: Such a doomsday weapon is not realistic, unless it is pretty much Herpes Simplex that also destroys your immune system some day in the distant future. A "quite harmless" thing that spreads and kills years later. $\endgroup$
    – Trish
    Commented Feb 5, 2018 at 9:57

I don't know enough about the biological possibility of creating it to say if it is possible but a virus that ends mankind doesn't need to actually kill anyone.

You could have a highly contagious virus with no obvious symptoms except leaving the hosts children infertile. In a few generations the last human dies peacefully of old age in a world that hasn't heard children for decades.

  • $\begingroup$ Welcome to Worldbuilding, Jedidiah! If you have a moment please take the tour and visit the help center to learn more about the site. You may also find Worldbuilding Meta and The Sandbox (both of which require 5 rep to post on) useful. Have fun! $\endgroup$ Commented Jun 29, 2018 at 13:14

Well ... maybe. This may be possible, but if so, it's right on the edge of the possible. The only way to find out for sure would be to try to develop such a weapon, and see how well you did: "try and see" projects are how technology moves forwards. I suspect that the degree of success could be significantly influenced by the individual motivations and brilliance (or lack thereof) of the scientists working on it.

For obvious reasons, people who know a lot about what you'd have to do in such a project are not talking about it.

It is not impossible to get highly talented scientists to work effectively on doomsday projects, but doing so does require that they have bought into an ideology that supports it. Some dictators manage that, and some don't.

  • $\begingroup$ Not necessarily require a dictatorship. An ideology driven armed group may do it if they have full control of a territory over an enough long period. $\endgroup$ Commented Aug 19, 2016 at 15:33

On reflection I say "no" as well.

To begin with, we can relax some of your assumptions. For example, viral reservoirs exist other than in wildlife (herpes uses the nervous system where we don't yet have a means of eradication but other virii use bone marrow where we are starting to have such a means). A period of asymptomatic infection (to allow spreading) followed by sudden death probably won't hinder postmortem diagnosis and discovery of the pathogen or slow down R&D into treatments once it's identified (it might even make it easier to find as it will be fairly clear there is a pathogen to locate and probably which organs it can be found in).

Mutation is a double (or triple) sided problem for your would-be genocide. It creates variants of a virus but says nothing about how likely the variants are to have similar effects or succumb to similar treatments (some pathogens keep key proteins fairly stable as they mutate, which is good for vaccines, in others like the common cold the mutation is in prime areas for targeting which makes those areas unreliable markers for a response). Also if the virus is too artificial and perfected, perhaps variants will be more successful in the sense of spreading, but not in lethality - a pathogen 'measures' 'success' by (and favours) replication above host death - the genocide may wish host death but if a milder mutation spreads more successfully then it will prevail in a moderately short time (some years to some decades, perhaps a few centuries at most), which has happened to several diseases. Additionally if it's too finely tuned to target human lethality then the parts of its DNA/RNA which do so are likely to be quite superfluous for virus replication (they don't have a replication promoting function) and this has two problematic effects: in any mutation they won't have any reason to be favoured for survival and will more easily be lost or lose functionality, and being human engineered hey are possibly quite precise in function (as many human creations are) - that's quite a problem for a virus intended to be lethal, since minor changes are more likely to cause them to lose the edge of design they have, or to"break" something and therefore to not to have the desired effect at all.

So perhaps we try a different approach. We might look for a "base" pathogen to work with, whose replication can be made highly dependent on some specific aspect of mammalian biology (much easier to accept collateral loss of a class/clade than to find some core biology that's extremely distinctive in humans). In this case its replication is deliberately tied to its lethality, because replication involves successful metabolism of some protein or cell-type which is ideally a small part of the human body and where damage/loss is lethal to human life. For example - and I'm reaching here because this isn't my field - a ferrophilic virus whose replication is tied in with breaking up of haemoglobin, or iodine, or which can somehow cross the blood-brain barrier or affects ATP metabolism or the energy cycle, or whose replication occurs in nerve cells where it can replicate with impunity.

But essentially this is a generic description of many lethal virii, and despite this none have gone the "destroy all people" route yet. Even the worst plagues with zero medical/scientific knowledge and zero hygiene haven't come close. Many virii are extremely lethal when they first "find" humans (syphillus, flu, bubonic plague, ebola) yet none came close to the effect sought here. All (except possibly the recently discovered ebola) also became milder over time as well, effectively exchanging massively acute impact for duration of host lifespan/spreading potential. The natural processes of pathogen/target/vector/mutation tends to heavily load the dice against this kind of effect (if it could, it would already). Its true that some entire species have been killed by pathogens (including some trees, not just mammals) but it seems other factors including the scale of response may have played a part in this, for example diseases of trees and wild animals don't get medical responses and knowledge rapidly piling in during an acute crisis anything like a human disease would get.

Returning to our pathogen. Suppose we do tie replication success to lethality at the start. Then we need to look at how it replicates beyond its host. The problem here is you want 2 contradictory things - extreme replication and extreme host lethality. If both were easy to obtain then syphillus/flu/smallpox/measles would have killed us all long before the concept of pathogens arose. All mutated into milder, more successful, replicators. The ones that are massive replicators and also lethal (cholera being one) are slower and in some cases symptomatically treatable.

Even indirect routes (water borne virii, destruction of some crucial part of the human food chain) won't help much - water and air can be filtered for virii, and foodstuffs (plant or animal) can be captive bred in virus-free facilities. One possible target might be the CO2->O2 cycle (virii that affected photosynthesising plankton/algae/plants) but such organisms are very widely spread and have survived geological time of pathogens, I don't think your genocide would have a hope of doing in the foreseeable future, something which 3 billion years of viral warfare has completely failed to do. That's without considering other practical issues for a pathogen, such as near-universal exposure and assuming near-zero immunity, and ignoring completely non-vaccine responses such as quarantine and isolated land masses.

Stepping outside the box, in theory there is a small loophole open, if you can find a way to deliberately infect all people at once. This approach sees the issue as one of vector not pathogen (finding a lethal pathogen is easy, finding one that can kill everyone too quickly to respond to is very hard, perhaps we could "rethink" the problem into "given a virus that's lethal now, could we infect almost everyone in a very short time, so hiding/spreading/mutating/vaccine aren't relevant", and in this way we bypass much of the design problem). The problem with this is there just aren't vectors which get enough people, or at least none I can think of. For example, simultaneous addition of virii to worldwide water reservoirs, manufactured food, medical supplies (sneaky!), or common objects that change hands quickly such as money - none seem likely to work.

My conclusion is that it just isn't that easy - that a would-be genocide will find it immensely hard. Forget magic time-delay virii, we don't have a way to do that now or in the foreseeable future. Whatever you put out there has a replication agenda not a deathly agenda, and that's what will prevail faster than you can kill all people out there.

  • $\begingroup$ Mutation is a double (or triple) sided problem for your would-be genocide. It creates variants of a virus but says nothing about how likely the variants are to have similar effects or succumb to similar treatments (some pathogens keep key proteins fairly stable as they mutate, which is good for vaccines, in others like the common cold the mutation is in prime areas for targeting which makes those areas unreliable markers for a response). just take vih, stable symptoms, currently start to adapt to drugs and peoples naturally immune. No vaccine can be created against it. $\endgroup$ Commented Aug 21, 2016 at 11:41
  • $\begingroup$ don't get medical responses and knowledge rapidly piling in during an acute crisis anything like a human disease would get Except if there’s no symptoms, then once they appear it’s a bit like if you can find a way to deliberately infect all people at once. $\endgroup$ Commented Aug 21, 2016 at 12:58
  • $\begingroup$ 1) No symptoms for a while isn't the same as a near-immediate and universal infection process, except for one thing in common - we don't have anything like a method to achieve either of them, either now or in the foreseeable future. 2) HIV is a good example of why its so hard not why its so easy. Natural processes and epidemiology are all against it, because the test whether a variant of a virus 'succeeds' is how much it replicates and not how much it kills, no matter the initial effect or the intent of its creator. HIV is much less lethal than other major historical diseases which had no cure $\endgroup$
    – Stilez
    Commented Aug 22, 2016 at 1:14
  • $\begingroup$ HIV is much less lethal than other major historical diseases which had no cure except you always end up dieing because of it without medication (except if you are immune naturally). This that point which is important : catching the built diseases will always kill you. $\endgroup$ Commented Sep 2, 2016 at 20:16
  • $\begingroup$ How does this change if we relax the targeting constraint, and just want to indiscriminately kill as many humans as possible? And what resources would be needed for this, could a lone lunatic or small well funded team deliver the goods? $\endgroup$
    – Innovine
    Commented Nov 10, 2016 at 7:21

What you need are so-called two-stage bioweapons, they are not only possible but it's very likely that Russia, China, North Korea and other countries are already busy working on obtaining such weapons. The use of such a weapon would be extortion to e.g. get rid of sanctions in exchange for a vaccine.

As pointed out here, advances in bio-engineering has made it possible to create smallpox ab-initio in the lab:

Eradicating smallpox, one of the deadliest diseases in history, took humanity decades and cost billions of dollars. Bringing the scourge back would probably take a small scientific team with little specialized knowledge half a year and cost about $100,000.

This means that it's only a matter of time before new viruses that have never existed before and which cannot arise due to natural selection, can be created in the lab. The most dangerous bioweapons imaginable can then be created. A simple way to make a very destructive bioweapon is to construct a very infectious, primary virus that itself does little harm, except that besides making copies of itself, it also makes copies of a different, secondary virus that causes a deadly disease.

The primary virus infects cells in the upper airways and spreads easily from person to person. The secondary virus is then produced by the primary virus in the upper airways, but it is not capable of entering these cells, and therefore won't spread by itself from human to human. It is designed to infect cells of other vital organs such as the liver to cause a deadly disease with an incubation time of many weeks. The idea is then that the primary virus will have spread around the world, with many millions of people infected and recovered from it unnoticed, when the disease caused by the secondary virus will start to strike, seemingly at random all around the world.

When scientist investigate this disease, they'll discover that it is caused by the secondary virus, but they'll at least initially, be at a loss to explain where this virus came from and how people got infected by a virus that isn't capable of spreading from human to human.

If North Korea was responsible for this bio-attack, then that won't be clear until they either claim the attack or when it becomes clear that there are no cases of the dreaded disease in North Korea. The North Koreans would then first have vaccinated their own population against only the secondary virus, and then they would have let the primary virus spread among their population. The limited contacts the North Koreans have with the rest of the World, e.g. via their diplomats, would spread the virus throughout the Word.

North Korea could have decided to launch such an attack in an effort to get sanctions lifted. Once the disease caused by the secondary virus starts to manifests itself, Kim would announce to the World that his country has been suffering from a terrible disease and that his heroic scientists have developed a vaccine and medicines against it. He is then willing to let the World benefit from the work of his hard working scientists, completely free of charge, with only the condition that the sanctions against his country will be lifted.

  • $\begingroup$ with current technology, not sure it'd work. gene sequencing is fast by now $\endgroup$
    – bytepusher
    Commented Feb 8, 2023 at 3:03

I've got to go with the no answer (atleast, no, not within 10 years), mostly due to this constraint:

  • Not showing any symptoms during years while still being contagious is the ideal overcome (but when the symptoms starts, kill the host within one week to avoid diagnosis). It would also allows the virus evolve in order to adapt itself against various natural defenses of it’s host (hiv is starting to doing it).

I get what you are going for here, you need near 100% infection rates before detection to really get a massive death toll...death too quickly results in identification and quarantining, limiting the virus's ability to infect. Seems like you've been playing that plague inc. game.

Virus's are among the most rapidly mutating 'living' organisms on the planet...their reproduction method almost always ensures mutation, even within one generation of the virus. To create a virus that goes for infection, then at a certain time mass mutates to a much more lethal version of itself isn't within the realms of what we can control.

Virus's also tend to specialize...what is good in one scenario might not be good in another scenario. A virus completely specialized to go after humans won't fare as well within other species. IE, a virus that can infect a bird has devoted some of it's resources to the ability to infect a bird (and some of it's surface area), limiting what it can direct at another species suchs as humans. You are asking for a virus that is specialized in all domains without sacrificing any ability in a different domain.

You're entering the realms of asking for a car with the turning radius of a go-cart, but the wheel base of combination truck...one advantage comes at the expense of another and you can't have both.

  • $\begingroup$ o create a virus that goes for infection, then at a certain time mass mutates to a much more lethal version of itself isn't within the realms of what we can control. Not needed, simply take vih which already do it (my ideal weapon might simply consist of giving vih more contagious vectors). Virus's also tend to specialize yes to some extents, however malaria is a good example which kills a lot of humans years while being able to live in mosquitoes. Maybe my vih like weapon might start to exist one day naturally due to the huge increase of monkey poaching in Africa due to our economy. $\endgroup$ Commented Aug 19, 2016 at 20:05
  • $\begingroup$ It only needs to kill humans, not animals, so if it don’t develop wells in animals this isn’t an issue. Also killing by auto immune induced virus was only a suggestion, aids spread doubt during 20 years after it’s discover. Though aids being well know, there won’t be as much doubt if something new uses it. $\endgroup$ Commented Aug 19, 2016 at 20:12
  • $\begingroup$ @user2284570: Malaria is not a virus. $\endgroup$
    – celtschk
    Commented Aug 21, 2016 at 10:33

This concept has already been well explored by Tom Clancy in his Rainbow Six novel (and at least one other).

The virus used there seemed believable, and the distribution method ingenious.
Little spoiler: he went for a genetically hardened version of Ebola, with a very clever way of distributing it (which I won't mention, read the book).
He touches on the same issue in Executive Orders, using a completely different distribution system.

Whether either could have worked in reality I'm not the biologist or bio war specialist to be able to say, but to the layman both scenarios sound plausible (which in fiction is really all that matters, isn't it?).


You said HIV wasn't infectious enough to be used as such a weapon of revenge. I think that is wrong. Instead of creating a stronger, deadlier virus you could use your lab time to create ways to spread HIV.

For example condoms are treated to be slippery and (some) to kill semen. Generate something that resembles this coating but contains HIV and keeps it alive. Then have people infiltrate factories to sabotage the production.

At the same time do something similar with factories for medical supplies, blood preservation, tattooing gear.

By doing that you can infect some percentage of the population. As tests don't work at once every infected person has a good chance to infect someone else before it is noticed and even after that it will take a considerable time to suspect and test the contaminated gear.

It is a slow process but I think if disruption is all you aim for it could work.


I'll say yes because you don't actually need something as comprehensive as you are describing. To see how to do this look to history for our guide--specifically the decimation of the new world due to old world diseases. Populations crashed, some areas were completely depopulated and that's without a lab being involved.

The key is diseases.

You don't need to engineer superbugs, just beef up things off the shelf.

A good starting point would be smallpox. Change it enough that the current vaccines do not work, do what you can to increase the lethality.

Now look around for other nasty bugs. Breed for resistance to vaccines and drugs. If you can up the lethality influenza comes to mind given how well it spreads.

Your bioweapon isn't one disease, it's as many deadly pathogens as you can come up with. Some people will be immune to one but that won't protect them from the next. The combination punches will be a lot more lethal than any single pathogen would have been.

Now take a play from Tom Clancy--not the stupid bug of Rainbow Six but the botched job of Executive Orders. (The pathogen was a version of Ebola that had some ability to spread by air.) Your target is trade shows. You don't have the security at trade shows that you have at airports, it will be much easier to deploy your weapon. Most attendees at a trade show are going to fly somewhere in a few days.

You're not going to get a 100% kill but you don't need one to bring us down. Once you punch enough holes (workers that are dead or hiding out instead of on the job) in the system the flow of goods that keep society working stops. Most of the world is now uninhabitable--even if you didn't kill the people they'll starve anyway. You'll have survivors in more primitive areas but you'll have more mouths than producers--fighting over the food will take priority over producing it. Once you have reduced the population below minimum densities the last ones will die out.

  • $\begingroup$ disagree. You can survive to smallpox. This would cause uge troubles but won t end mankind. By contrast, aids adapt to the natural defense of it s hos. $\endgroup$ Commented Nov 11, 2016 at 14:07
  • $\begingroup$ @user2284570 Smallpox by itself wouldn't do us in. I'm saying to use a whole bunch of diseases all at once. Despite the much slower spread of the diseases it actually did get a 100% kill in parts of the New World. $\endgroup$ Commented Nov 12, 2016 at 8:28

As someone with a degree in biotechnology, what you want is no viable with modern day technology.

If you want something to kill people after a period of ten years, I would suggest some form of parasite that could stay dormant for longs periods of time.

  • $\begingroup$ Supposing such parasites can be transferred through aerial vectors during the asymptomatic phase. Otherwise, it’s like ʜɪᴠ (ʜɪᴠ is currently adapting to naturally resistant patients and triterapthy). Of course a research project would be involved. $\endgroup$ Commented Feb 5, 2018 at 1:36
  • $\begingroup$ Why not a fungus then? Some thing that could be spread trough most major cities without much concern, their spores could keep spreading and multiplying. $\endgroup$
    – Sasha
    Commented Feb 5, 2018 at 1:36
  • $\begingroup$ Providing creating it. Because fungus which always kills it host after a long asymptomatic phase like ʜɪᴠ and can be transmitted like influenza doesn’t exists yet as far I know. But fungus acts most of the time through producing toxins, which means creating a vaccine may be possible. Unless the parasite directly attack sells like Malaria (though Malaria isn’t a good example because you can survive some cases without treatment). $\endgroup$ Commented Feb 5, 2018 at 1:46

I've just written a short story about biological weapons and done a little bit (really a little bit, by far not an expert) on the topic.

You will never wipe out humanity with a virus. There is too much distance and variance and too many detections and something like a multi-year infection period with a high infection rate but no symptoms and then suddenly death all over the place just isn't realistic.

If you want to kill humans, you need multiple stages. If you are a nation state with sufficient resources, you can accomplish a very high kill rate if you are really determined to do so. Your diplomats, tourists, trade delegations, etc. can spread an infection without symptoms to every corner of the world. That will in a good scenario kill millions, maybe tens or hundreds. But anything more than that would be extreme luck.

But if you can come up with an antidote in time of need and use that to deliver a second stage - now we're entering the realm of SciFi here as I don't think the genetics exists yet to create something like that - and at least for a short time you are the only supplier of the antidote, when the need is at the highest, you can go into the billions range.

With the widespread social and economical disaster that would follow such a crisis, you can go to conventional warfare to spread a third disease (i.e. just spray an aerosol like they did with Agent Orange), and simply overwhelm the medical capabilities of whatever is left.

Of course, that assumes that your country isn't hit the hardest and your military still follows you and is still operational after all of that and your biolabs are still willing and able to produce the bad stuff in enough quantity - it's all a very big stretch, and you might vary the details, but the basic message is that something like wiping out humanity is not going to happen with a single attack, no matter what borderline-magical capabilities your virus has.

  • $\begingroup$ ʜɪᴠ is the proof of the contrary. The virus itself is starting to adapt to tryterapy as well as peoples with so called genetical protection. My question is about developping a weapon without the possibility to create an antidote. The fact ᴀɪᴅꜱ isn’t the perfect candidate is the requirement of having sex or using drugs (which means poor vector). $\endgroup$ Commented Jan 3, 2019 at 15:00
  • $\begingroup$ I don't think you can ever exclude the possibility of an antidote. The antidote may be extremely difficult to find, but a virus that in principle doesn't have one? Unlikely. $\endgroup$
    – Tom
    Commented Jan 3, 2019 at 15:25

If the intention is to basically take revenge and eradicate the human race: How about a virus that affects fertility and/or pregnancy? It seems to have almost no immediate effect, but spreads extremely well (like Covid, but only mild cold symptoms, if any) - but everyone infected becomes either infertile, or will transmit the disease to the baby, causing issues during pregnancy.

Most people wouldn't even notice the virus - maybe just some sneezing, and thus wouldn't visit a doctor immediately. Noticing infertility probably takes a while - giving the virus time to spread even further - spread through air, this could be highly effective.

Of course, it would take a long time for humanity to die off - and there's a fairly long time window in which they might research ways around it - but some problems are perhaps simply not solvable. AIDS took a long time to be able to treat medically, and there's still no vaccine...

  • $\begingroup$ I wouldn t call aids treatable. Heart attacks, kidney failures and chronic pain as secondary effects of treatment. I heard several peoples who opted out of the triterapy as a result despite being infected (including 1 in front of me). See also en.wikipedia.org/wiki/Artificial_womb#Gender_equality_and_LGBT $\endgroup$ Commented Feb 11, 2023 at 7:47

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