We are an interplanetary human empire at war with an alien species. On the brink of defeat, this alien species designed a virus to turn the tide of war. This virus is airborne and highly contagious, and disrupts the brain's ability to use serotonin.

Alien spies have released the virus into the local birds--the virus is related to the avian flu--after trying and failing to gain access to the water distilleries. The outbreak begins.

The population is about ten billion people, and due to sustainability issues, most of the planet is functioning at the same level as the modern American middle class. Population density is still crammed near the coasts because traditional ships are cheaper than launching into orbit.

My question: About how many people would this rage-inducing flu virus have to infect worldwide before the planetary security forces (numbering 125 million) become overwhelmed and have to call for military aid?

Less than a year before this outbreak, the aliens launched a failed attack on this planet that killed and injured many security forces, incapacitating about a quarter of them. The security forces have aircraft, but due to budget cuts in local police forces, they have very little in the way of ordnance to fire from their limited number of police drones (think 10,000 remote-controlled drones with rapid-fire machine guns).

Security officers are equipped with non-lethal riot guns that are designed to make a large photon beam that induces temporary blindness and a loud noise. They are equipped with tear gas. The first human outbreak occurs a week after the spies introduction the virus into the bird populace in the Planetary Central Security Department. About 5% of the 125 million man police force became infected. When these officers went home, they spread the virus to all they came in contact with. In two days, the flu-like symptoms of the first of the infected began to subside, and then the neurological symptoms set in.

Since the blatant murdering of civilians is prohibited and is punishable by death, the security forces are not issued lethal weapons. The few projectile weapons they have (including their aircraft ammunition) are designed for crowd dispersal. For example, the majority of drone ammunition is designed to release small amounts of tear gas and chemicals that cause slight burning of the skin.

  • $\begingroup$ It could be as few as 1,000 infected making billions panic (including the security) or it could be billions of infected that are contained by the well trained and equipped planetary security. This question is very broad. It's going to depend on all the little battles. $\endgroup$
    – Samuel
    Commented Mar 16, 2015 at 16:10
  • $\begingroup$ @Samuel Too broad? Can you see the question being salvageable through an edit? $\endgroup$
    – Jax
    Commented Mar 16, 2015 at 16:12
  • $\begingroup$ I would suggest focusing on a particular skirmish. Describe the security forces position and situation and try to get a rough number of infected to overwhelm that situation. $\endgroup$
    – Samuel
    Commented Mar 16, 2015 at 16:16
  • $\begingroup$ I'll try to narrow it down. $\endgroup$
    – Jax
    Commented Mar 16, 2015 at 16:27
  • $\begingroup$ Not to be a pedant, but serotonin inhibition will not get you a rage filled victim. Serotonin is just one of a number of neurotransmitters that plays an important role in regulating mood. Glutamate and dopamine are two other critical neurotransmitters. Furthermore, a lack of serotonin is also associated with depression and pessimism. While also associated with increased distrust and cynicism, these symptoms would not lead to a zombie-like overthrow of your government. $\endgroup$
    – Nick2253
    Commented Mar 16, 2015 at 22:44

4 Answers 4


I have issues with your world-building, I'm afraid.

You explicitly distinguish between security forces and military. A security force level of 125 million for a global population of 10 billion is quite extraordinary. The US, with a high level of violence, only has a full-time police force of 120,000 for a population of 300 million. Extrapolated to 10 billion that would be about 4 million. Note that the US homicide rate, about 16,000 for 2013, is roughly 1 homicide per 7 LEOs, so most cops don't see more than about one homicide per decade.

This suggests two possibilities: either an extremely violent society or an extreme level of governmental control of the population, and neither seems consistent. With a violent population the police would seem to need the option of lethal force, yet you've ruled this out. Likewise, tight governmental control would prevent the budget cuts you've invoked.

Additionally, the first wave of rage would obviously hit the security forces first. You've got about 6 million of them infected, and this first wave is going to make the populace stop paying attention to the police. And the second wave is obviously going to impact the security forces as well - think one person sneezing at daily roll call. Oh yeah, and how did this selective infection work, anyhow? Was there a police convention with 6 or 7 million attendees? Any sort of infection working down the ranks is going to hit families just as fast.

As a direct answer to your question, I'd have to estimate 2 weeks or less. Assume an incubation period of 3 days, an infectious stage which coincides with symptoms, and a multiplication factor of 5. Starting with 6 million infected people evenly spread out over the planet (so no geographical quarantine measures work), after 5 days you've got 30 million, at 10 days it's 150 million, and at 15 days it's 750 million. With the security forces the obvious infection threat, there is no credible force to maintain social order.


The answer ranges from 'they will never overrun the planetary security forces' to 'an unknown, very large number' to 'very few'. Dependent on a few factors.

First off, if we do not assume that the 'rage-virus' works as prescribed...then the virus might simply be lethal. Utter lack of serotonin in infants has been linked to Sudden Infant Death Syndrome...it is believed that lack of Serotonin in the brain stem harshly impacts the autonomic nervous system as it relates to keep the heart beating and the lungs functioning. Resulting in cardiac arrest/lung failure (suffocation). At this point, they will obviously not be overrunning the local security forces. Even if it isn't fatal, the decreased heart rate and breathing difficulties will critically impair the 'rage-virus' infected.

Second, we have to consider initial saturation to determine if a quarantine can be established in time. If the infection is localized at first, then quarantining the area, then firebombing it enough times will burn out the virus.

And, finally, the most important factor is Force Multiplication. Even if the rage-driven humans still have enough mental faculties to use modern weapons, and if they have access to weaponry...their equipment will be inferior to military-grade equipment like a security force has...and they will have absolutely zero tactics, as they are engaged in a rage-fueled blitz (and rage tends to screw up your aim and ability to operate advanced machinery). Adding more 'infected' to the mix is an additive factor to damage done. Improved weaponry and tactics is a multiplicative factor. This is part of why a zombie outbreak would never actually work against the military. Advanced weapons, training, and tactics is much more valuable than 'more people.'

In short, if the security forces have fortifications of any sort and are sufficiently well trained to manage the panic that would break out, they should...if nothing else...be able to bunker down and hold out for as long as they have supplies. It is possible to overrun them eventually, but it all depends on what sort of weaponry the security forces have, and how well trained they are. If they have wide-area weapons with near unlimited ammunition (like a Microwave Emitter or Sonic Weaponry) then they could probably hold out against the unorganized, rage-infected indefinitely. Then there's the question of air superiority. It is unlikely that a rage-infected will be able to operate aircraft...and airstrikes, napalm, or even a guy in a helicopter with a machine gun, can easily turn the tide of a battle.

Of course, if the defense forces are infected first...which would be the smart thing to do tactically...then it could take very little to overrun the remnants of them.

  • $\begingroup$ Just for the record, the goal of my virus is not zombies, just mass panic followed by collapse of society. After the military is withdrawn from the frontier to maintain order, the aliens will launch an offensive. As a possible side question how much serotonin loss would be survivable and induce a sense of violence and anger great enough for society-destroying riots. $\endgroup$
    – Jax
    Commented Mar 16, 2015 at 16:17
  • $\begingroup$ It depends upon the security force's authority to execute lethal force. If they can easily identify and shoot people terminally subject to this virus, then they don't really need the military, do they? $\endgroup$ Commented Mar 16, 2015 at 16:23
  • $\begingroup$ Seeing as no one has tried it on humans...it's hard to give you an exact figure. But the factors I listed still apply to inducing mass panic. A highly trained security force with advanced weapons could shut down the infected area before panic spread too far. And there are cultural issues around mass panic as well. Look at the different behaviors seen between the aftermath of Katrina, and the aftermath of the Tsunami that hit Japan... $\endgroup$ Commented Mar 16, 2015 at 16:25
  • $\begingroup$ Oh, and Serotonin deficiency tends to lead towards OCD-like symptoms, along with Anxiety and Depression long before it leads to increased aggression. In fact, in some people...the virus might just make them start washing their hands obsessively, or organizing their writing utensils, rather that raging out... $\endgroup$ Commented Mar 16, 2015 at 16:28
  • $\begingroup$ This appears to be a long commentary on the question rather than an answer. If you find the question to be unanswerable, then say so in a comment. $\endgroup$
    – Samuel
    Commented Mar 16, 2015 at 16:40

Your question seems to be focused on the military impact of fighting/containing the infected population. There are a lot of additional factors that you need to consider to answer the bigger question of can the planet be saved at all? You need to define the behavior of your virus, society, and key decision makers. You also need to factor in interplanetary relationships and the importance of this world in the overall power structure. I mean sure, the US manages to contain the outbreak around Phoenix, but then a new ones are discovered in Denver, New Orleans, Boston, and Seattle. What then?

What is the political structure of your society? Who are the individuals in key decision making positions? What are the bureaucratic power blocks and rivalries? How well do the key decision makers get along? Are the people in key positions willing/able to make the hard call that will piss everyone off? Will the population at large follow the edicts that come out of the government? Or do they scoff at it? How long does it take for the authorities to recognize what is going on and come up with an effective response? Quarantines only work if you know to put one in place, and political leaders (particularly in democratic societies) are often resistant to disrupting the lives of the general population by imposing harsh measures. There will often be an air of denial among the political leaders and the public at large in the early stages of a crisis situation i.e. "things aren't that bad", "you're exaggerating", "that is a matter for the local authorities", "why should I risk my assets/reputation because you were to incompetent to take care of this on your own". The sooner the powers that be recognize the magnitude of the problem and decide they are going to act without worrying about public opinion the better chances they have of containing the outbreak.

You also noted that your infection crosses the species barrier. What impact does it have on the birds? Does it kill them off and we get infected by their corpses? Does it make them more aggressive so that they have more direct human contact? No noticeable impact so there are no clues that they are carriers? Key point here is can they continuously reinfect the human population?

Can the virus infect life forms other than birds/humans? Do people have to kill off their pets? Can livestock become infected? Can people be infected by eating contaminated food?

Are there native plants/animals that might react to it? Would they give any clues as to the nature of the infection? Make it spread faster? Slower? Be a potential cure?

Is there a means of effectively keeping the infected animals away? As an example consider what would have to be done to clear all of the birds out of Chicago, and then keep them out? How would you keep birds from other regions from coming in and breaking your quarantine?

What is the incubation time on the infection? How long can someone be a carrier without obvious symptoms? Is there a way to detect the infection before obvious symptoms set in? Is the medical science of the society up to developing such a test and mass producing it? Is there a treatment/cure for the infection? Are there people who are naturally resistant? Can people be carriers and never show symptoms? How robust is the virus when outside a host? Can it lay dormant and reinfect people at a later time? Are there simple precautionary measures that a layman can take to avoid infection?

The nature of the virus and the political response are the key elements, not the raw number of people.

If we take the rage virus from 28 Days Later as our example. The time from exposure to rage is about 30 seconds. So one infected person getting into a crowded shopping mall becomes 2 after 30 seconds, 4 after 1 minute, 16 after 2 minutes, is pushing 1000 by the 5 minute mark, and over 1 million by 10 minutes. Of course somewhere in there the uninfected are going to notice what is going on and start to flee, which slows the rate of infection. Point being that non lethal weapons have no hope of containing such an outbreak, so it is not a question of whether the security forces can keep from being overrun so much as when do the political leaders admit that they cannot. (and is anyone technically capable of calling for help left among the uninfected when they do.)

If our virus is more subtle, slower, and/or less violent, then other scenarios become possible. But you still have to be able to effectively combat further infections, not the infected population in order keep things under control. If the virus is left unchecked, your society is doomed no matter what the security forces do.

All that said, I can think of very few things that would cause the military to deploy to "restore order" while they are already engaged in an interstellar war. The most I would expect them to do is establish a blockade and quarantine the planet so that the infection does not spread elsewhere. About the only plausible circumstances would be if the planet produced something that was somehow critical to the war effort, AND no one figured out that there was a bio-agent at work.

  • $\begingroup$ It's generally useful if you can answer some of the questions you put forward here. While these are all valid considerations, this answer doesn't actually answer the question - just expands the scope. $\endgroup$
    – ArtOfCode
    Commented Mar 16, 2015 at 18:06
  • $\begingroup$ I have actually considered all of the questions you put forward here and have answers. I simply didn't think that including whether a pig can become infected had anything to do with the question I asked, therefore I didn't waste time and space typing out every single detail pathology of my virus...Questions should generally only contain information possibly vital to the formation of an answer. $\endgroup$
    – Jax
    Commented Mar 16, 2015 at 18:13
  • $\begingroup$ @Dustin To my way of thinking they are all relevant to the question of can the local security forces contain things? Or do they need to call for help? Taking just the points of can a pig be infected? and can humans be infected by eating contaminated food? It impacts the effectiveness of the security forces based on the safety of their food supplies. If your front line troops suddenly become infected and turn on you because they decided to roast the wild boar that got tangled in the perimeter fence, you very likely just lost that battle. $\endgroup$
    – Rozwel
    Commented Mar 16, 2015 at 18:22
  • $\begingroup$ I didn't ask if they practically could contain it, I asked how many infected, given the circumstances of the Police, would it take to plunge this planet into chaos and make the military deploy to the planet instead of against the aliens. $\endgroup$
    – Jax
    Commented Mar 16, 2015 at 18:24
  • $\begingroup$ I've mixed feelings on this answer. I want to downvote it because it's more questions not an answer, but I also want to upvote it as the questions are very pertinent to the question being asked and actually might help the OP. $\endgroup$
    – Tim B
    Commented Mar 16, 2015 at 18:34

I'm going to side step for a moment the mechanics of a serotonin centered rage virus. I don't know tons about brain chemistry and I'm no epidemiologist, So I'll leave those aspects to my betters.

The short answer to the question, though, is not very long at all. And it has less to do with the numbers of LEO's (Law Enforcement Officers) than you might think

Your last couple of paragraphs caught my eye. You society places huge importance on life, to the point that non-lethal weaponry are the norm. In the presence of this kind of panic, this is going to change VERY fast.

In many places LEO's are trained that you do what you can to shut down bad situations with as little force as possible, but you also try preserve the lives of yourself and your comrades. You can't help anyone if you go down, sort of thing. There is going to suddenly be ENORMOUS pressure for special dispensation to use lethal force until the viral outbreak is contained.

The point of any law enforcement weapon is to get the perpetrator to stop whatever they are doing. One enraged guy can cause a helluvalot of damage and is difficult to get under control. With current non lethal weapons, he can still get up and keep fighting after a number of things like Tasers and pepper sprays and even bean-bag shotguns. The most reliable way to put a crazy one like this out of action is to use a few rounds aimed at center mass. This is all with Just One Perp. Now imagine you have a group of them.

At that point, you need to get as many under control as you can as fast as you can. The callous way to think about it is "Dead" = "Under Control". A fig leaf for this strategy is that shots to center mass may not be lethal, but they are the fastest way to get a rage monster to stop. As abhorent as this may sound to your guys, it will be the only way they get to survive at all. Small arms will be distributed by the military, as much as they can spare.


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