We have an outbreak of a zombie-like disease in major metropolitan areas. The disease itself has a slow incubation period, and after a time it becomes clear that it is spreading faster than they can handle, and it is time to try and close off the infected cities.

There are two primary goals:

  • quarantine the people within the city, because any number of them may be infected
  • keep the "zombies" from getting out

So the questions are:

  1. How would you actually physically accomplish such a thing with a huge city?

  2. How long would it take to get into place?

    • Bonus points if anyone could address issues specific to cities like New York, Chicago, and Pittsburgh.
  3. Let's talk about politics and legality too... There's no way this could be accomplished without resistance. What are the legal issues?, who would be in charge (FEMA?) and how long would the debate delay action?

  4. Could this actually work?

  • $\begingroup$ But it is possible? By the time the authorities decide to quarantine the city, it will already be too late. Depending on the incubation period, it is very likely that other cities will already be affected. If the spreading rate is low, then maybe then can control the epidemic this way and deal with other infected in a case by case. $\endgroup$
    – Vincent
    Commented Oct 11, 2014 at 15:45
  • $\begingroup$ Are we talking slow zombies or sports zombies here? Also, I assume they're dumb zombies and can't use tools or anything crazy - this doesn't make a huge difference, but it might alter a few parameters, such as how long it takes them to spill out of the city. $\endgroup$
    – mechalynx
    Commented Oct 11, 2014 at 16:38
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    $\begingroup$ Also, I am sooooooo tempted to make a "zombies" tag. Hold me back! $\endgroup$
    – mechalynx
    Commented Oct 11, 2014 at 16:40
  • $\begingroup$ can we have too many tags? what about a zombie society ? If you played ''Plague Inc: Evolved'' on Steam: store.steampowered.com/video/246620?l=french $\endgroup$
    – Vincent
    Commented Oct 11, 2014 at 17:25
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    $\begingroup$ YEAH FOR ZOMBIES TAG!!! $\endgroup$
    – MadPink
    Commented Oct 12, 2014 at 13:26

6 Answers 6


I'll assume people panic and try to get out (otherwise this will probably work a lot more easily).

Probably the first action you'd have to take is reduce the effects of panic, which would cause people to attempt to flee en masse and cause all kinds of havoc, including problems related to quarantine.

The Lie

So you lie, but in a convenient way, so as to reduce people's certainty that fleeing is the optimal option. You broadcast that the outbreak has been identified, teams are working on a permanent cure and that people should attempt to return to their homes if they are within the city or stay at work or wherever they are if they live outside it. Claim that teams have already been dispatched to provide medical treatment, examinations for infection and temporary vaccination. You must not present this as an attack - it must look like this has been going on for a while and that people have already figured it out.

In the case of NYC, which is what I'll assume we're placing under quarantine, as an example, there is a so-called "syndromic surveillance"[13] system they've implemented to monitor disease outbreaks - this plan includes vaccine distribution centers as well - thus, in the case of NYC, it's very easy to get people under control until military lockdown.

Many thanks to KaguraRap for this info.

Also, updates should also be broadcast, even if they're fake. This is to give the impression work is getting done and the plan is working and already under way.

This of course won't influence everyone and it doesn't prevent accidents and problems overall - random zombie attacks will happen, people will go insane etc. but it will reduce the amount of people that will flee until you can lock the city down. The idea is to present the danger as smaller than it is - you confuse them enough to pause.

All means should be used - police helicopters, radio, tv, everything.

The lock-down

You'd have to immediately dispatch police and military nearby to close off all roads leaving the city (obviously). While unlikely to happen, people might still attempt to leave using the sea, if the city has access to it, so you should dispatch coast guard to prevent this.

You also make sure there's enough personnel wearing medical clothes or quarantine suits - chances are you'll need them anyway to make sure that those who are maintaining the lock-down aren't getting infected in the process.

A few policemen and military units should scan the perimeter and prepare to set it on fire, if necessary. This is assuming that around the city, there's rural or suburban areas, so you're not going to burn people's homes.

All these people should share the illusion that this is already taken care of and it's just a matter of time until it's resolved.

The lie must keep being broadcast all the time - people might have missed it the first time and others might get convinced more easily when faced with the difficulty of leaving. They should be told that the lock-down is a precaution against infected people leaving and zombies escaping.


Eventually you'll have to send troops in to separate people from zombies and clean up. They'd have to look calm and in-control as much as possible and should enter from prominent city entrances (large, main streets). This gives people somewhere to turn to and go to. As soon as possible, units should scour the city for survivors and zombies, sending anyone who isn't a zombie yet to testing, explaining the routine procedure and promising vaccination.

People should be given placebo injections as part of testing and those who are infected should be taken to "monitoring" sections. Those not infected should be commandeered to keep things in order.

Keep people occupied and focused away from fleeing until it's too late.


Once enough troops are in, people are divided enough and exits are blocked, you should have good enough quarantine that, if there's a huge second outbreak, you can just order everyone to stay put while you burn the city down. Start from the perimeter.

Of course, the question is, do we have the time and people to make all of this happen?

For the following numbers and calculations, remember I am making huge arbitrary assumptions and have no idea about epidemiology, disease spread and related topics. Without knowledge of how fast people get infected, how long it takes to turn into a zombie, how long for symptoms to appear etc. there is no way to compute how many people are going to be zombies and how much time people had to figure out what was happening.

First of all, how virulent is this disease? I'm going to assume 0.02% have turned into zombies out of 50% infected at the time actions are taken to contain the outbreak. Assuming this is New York City, that means we have about 20 thousand zombies, 5 million infected and about 5 million not infected (I'm assuming the City + people who are there for shopping, traveling, tourism, business and people passing through = 10 million). I'm assuming about 20e3 zombies because that way, across the area of the City, which is 1,214 km^2[8], we get about 16.5 zombies per square kilometer ( 16.44 z/km^2 ). This means, factoring in the population density which is 10,725.4/km^2[8], we get a zombie to civilian ratio of 1.54e-3, which means 1 zombie per 650 people (this ratio, if we take Dunbar's Number into account - which says we can maintain 100-150 relationships as humans - and this article, which seems kind of terrible but references a study that claims the average american knows about 600 people, indicates that by this point, about 1/3 of the population will have heard something and may suspect something is going horribly wrong).

I'm using this amount because I assume, after having this many incidents of zombies, many of which will be taken to hospitals or attack people, over a period of a few days, it will be enough for alarms to go off (think of it as a disease - you're a doctor getting tons of incidents with the same horrible symptoms and the patients becoming murderously rabid after you think they're dead - it would look like ebola and rabies on steroids!). In other words, I'm assuming there is an attempt to quarantine the city after there are enough similar incidents around the city that pretty much everyone will have heard something and hospitals can consider it an epidemic or attack of some sort.

The US has a density of 4.4 military personnel per 1000 capita and a density of 248 police personnel per 100000 capita. Converting the ratios so that we can add them, we get 2.48 police and 4.4 military per 1000 capita, a total of 6.88 people per 1000 we can have contain the city. For New York, this would mean about 69 thousand people, but we can use the NYPD's actual numbers[11] which state that there's 34.5e3 uniformed in service, which brings the total up to 78.5e3 uniformed personnel. Add to this about 942 fire departments[4] and about 34e3 firefighters, 2/3rds of which are volunteers. Thus we have a total of about 112.5e3 personnel that can help lock down and quarantine the city.

Going by this article it seems we need 60-200 military troops per civilians to occupy the city and lock it down. With our numbers, we have 127 soldiers and police per civilian, so we should be good, considering these are infected people, disorganized and not likely to fight back.

Going by the automobiles per capita for the US which is 800:1000 approximately[12, we can assume we have about 8 million cars in the city. Assuming most people will want to take their families with them before fleeing and that some will have relatives and loved ones in hospitals or will be tending to them (or waiting for help), lets assume a third of the population gets in their cars and leaves. That gives us about 2.5 million cars leaving. I expected the police to have, say, about 1 patrol vehicle per 16 police officers since precincts reuse vehicles (are they all called officers? I mean personnel), which would give us 155 police vehicles, which is not much, but going by actual NYPD numbers[11], it seems they have 8839 cars, 11 boats, 8 helicopters, 60 horses (lol) and 34 dogs, which is a lot. We have to assume the military brings in their own vehicles, including tanks, but I can't make an estimate on those (it would depend on what kind of corps have camps nearby, the speed of these vehicles on a highway, how many can be deployed from nearby etc.).

Can these police cars form a blockade across all entrances? Lets see. Going by this map:

Map of New York

we can see that the highways leaving NY are 95, 87, 1 and 278. I counted 12 entrances through highway, to the city, which is how most people will want to leave. That gives us almost 736 police vehicles per highway - too many. We can also count on the military again or call in the fire department to plant their 950-1900 fire engines across the highways, using hoses to prevent rioting. This way, we can have 950/12 = ~80 fire engines across the highways if we're fast and send all the police cars to block smaller exits and maintain some control until the military lock-down.

Police should also shut down and block all subways early, as KaguraRap reminds. See the comments for more.

So far, assuming the threat is recognized in reasonable time, we should have enough people, vehicles and time to lock down the city. You can't really get a perfect containment within a few hours, but I think that there's going to be enough time and quarantine is possible. To get those that escape the city, you call all the surrounding police stations and tell them to keep watch of the road, block all cars from passing through, especially those coming from NYC.

oh also, I think I earned that zombie tag, so I made it :P

  • 1
    $\begingroup$ Just to elaborate on the "lie" part, you might want to check out NYC's disaster website: nyc.gov/html/oem/html/hazards/hazards.shtml It has info about evac zones and what they'd expect civvies to do depending on the disaster. If they're spreading a lie that it's a disease outbreak, they might open centers that hand out "vaccines" and the system to monitor outbreaks in NY (syndromic surveillance) is the original model that the rest of the nation uses. Also keep subways in mind, there are a lot of New Yorkers who don't have cars. nyc.gov/html/oem/html/hazards/events.shtml $\endgroup$
    – KaguraRap
    Commented Oct 11, 2014 at 23:19
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    $\begingroup$ And with NY being on high alert due to terrorism, ever since 9/11 when you're on a train or a bus, they're constantly announcing that you should be keeping an eye out for suspicious packages or behavior. I imagine they'd take advantage of that same system to announce instructions to New Yorkers and encourage them to hunker down versus trying to leave the city. There are already soldiers stationed at some major terrorist target points in the city e.g. Grand Central Station, Penn Station, and so on, so I don't imagine getting military personnel or officers in the city to be difficult. $\endgroup$
    – KaguraRap
    Commented Oct 11, 2014 at 23:23
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    $\begingroup$ lol your answer is accurate though. I think what also makes NY interesting is the fact that native New Yorkers are so used to hearing these "terrorist" announcements that they've developed one of two mindsets. 1) Meh. Same crap everyday. Pay it no mind and go to work or 2) OMG we can get attacked at any time, now I've gotta be paranoid! So with those two groups, you've got the NYers that aren't going to heed the "hunker down" instructions because they zoned it out, or the paranoid types that will either survive because they're on high alert or panic run right into a zombie. XD $\endgroup$
    – KaguraRap
    Commented Oct 11, 2014 at 23:40
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    $\begingroup$ @ivy_lynx Wow, you're even more ruthless than I was! $\endgroup$
    – HDE 226868
    Commented Oct 11, 2014 at 23:52
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    $\begingroup$ @ivy_lynx Assumptions schmassumption. The population is really only 8 million or so people. Unless you plan on taking out some of the tri-state area. I did say that Newark International would be an issue. . . $\endgroup$
    – HDE 226868
    Commented Oct 12, 2014 at 0:10

How would you actually physically accomplish such a thing with a huge city?

  • Barbed and razor wire. Barbed wire would definitely tangle up zombies. Although the fact they can't feel pain means they could pull free with damage. If you setup enough layers the chance of getting through is reduced.
  • Concrete and Roads. The pre-made concrete such as blocks and sewage sections can be shipped and put into place relatively quickly.
  • Pits, Moats, and Flooding. Collapsing existing underground structures and dropping bombs to quickly dig ditches and redirect rivers.
  • Precision Demolition. You can collapse buildings to form barriers if you have enough tall towers. They aren't particularly effective but might be better than nothing.

How long would it take to get into place?

  • If it's a water-bound area like Madagascar you would enforce naval barriers to prevent movement in and out. That can be interpreted as instantly.
  • Demolition based could also be done really quick
  • Wire and road re-use is next fastest as evidenced by trench building and the Berlin Wall. This is really only limited in speed by manpower.
  • Large concrete structures would take time to build and only become feasible when the volume of concrete needed is small.

What are the legal issues, who would be in charge, and how long would the debate delay action?

  • Until the civilian ratio is low enough to stop outweighing the threat. This can be relatively high but I'm suspecting your looking at <50% civilians.
  • If the nation effected is nuclear then they have final say (probably the only say actually). And the military would take over.
  • For non-nuclear countries, at global scale everyone would be a piece in the game. Military and international organizations are the only ones capable of mobilizing the necessary resources so they would be the major players. You would of course see the Red Cross and other Disaster Relief organizations helping to save civilians.
  • As seen by our response to threats like cross-species transmission and the Black Death. We really don't respond the best to sudden threats (which is why we resort to martial law). Debate would probably last long enough to test if they could be saved which would require a capture team and some scientists. I'm thinking a week would be enough.
  • If they could be saved then you have massive legal and ethical issues which prevent anything other than quarantine from occurring. We would probably form an international organization similar to the UN if not directly operating under it. Expect it to be delayed for massive amounts of time as politicians and human rights groups debate. Months if not a couple years. You can definitely kiss the immediate uninfected areas goodbye.

Could this actually work?

Yes, but it's highly situational. As your total perimeter size increases (number of infected and size of them) it becomes less viable to quarantine in an enforced way, which is the only way you'd want to do. Zombie concentration and smaller areas lend more to air-strikes and will consequently lead to less quarantine activity. When its all blown over the infection sources may be post-disaster quarantined to prevent another outbreak. Even if its the least likely for a given scenario, as soon as someone discovers a way to save the victims (even if it only works for a little while) expect quarantine measures to show up.

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    $\begingroup$ It ended up getting deleted from my answer, but its probably best to note that quarantine is only really mentioned in passing for CONPLAN 8888 / CONOP 8888 which are the USA's actual plan on the subject. There's no compelling reason to not just nuke the whole infected area if it gets bad enough. $\endgroup$
    – Black
    Commented Oct 11, 2014 at 21:10
  • $\begingroup$ Bonus points for mentioning Madagascar. It's one of the most impenetrable fortresses for diseases and the like. Also, nukes are fairly effective in disabling infected cities. The political implications however are severe. Not that a zombie outbreak is good for your career... $\endgroup$
    – Mast
    Commented Oct 12, 2014 at 15:19

could this actually work?


In all of history, no one has succeeded in quarantining a population larger than a few hundred. It's a fictional idea. Looks exciting in a movie, never work in real life, especially in the highly mobile world of today.

The fundamental flaw is the idea of a mass quarantine is that infected people don't bunch up anymore in specific areas but show up sprinkled all over the country following major transportation routes and nodes. Owing to this mobility of the population the uninfected are effectively surrounded by the infected likely before the actual scope of the problem is recognized. It's like fighting an enemy whose is mobile when you are static. Your only choice is to turn hedgehog.

Instead of mass quarantine, we would use a reverse quarantine.

A reverse quarantine, also known as a triage quarantine, concentrates on protecting essential personnel and systems instead trying to isolate the infected. Its never been used on a large scale and where it has been used, they concentrated on protecting medical, technical and transport personnel needed to respond to the disease outbreak.

In a zombie scenario, the strategy would be not to try to confine the infected and zombies to a small area because they would already be widely spread. Instead, the uninfected would create defensive pockets all over which could be quarantined from outside contact and protected from active attack. Such pockets could be anywhere even in individual buildings inside major cities. Inside the pockets they would ride out the plague.

how would you actually physically accomplish such a thing with a huge city?

The only possible means of quarantining a major city would be with area weapons and free fire kill zones. You wouldn't try to block transport routes but instead define an area of ten to twenty miles deep around the city. (That depth is necessary to prevent someone from walking across it entirely at night.) Anyone or anything detected moving in the area would be fired on instantly using aircraft and artillery with ground troops in MOP coming in only at the far edges as the final measure. Even then, you would likely have to resort to laying down chemical weapons over broad areas.

Such a system could not be put in place without a lot of preparation because the troops would not carry out such horrific measures (they'd have to fire on children for example) unless they were all convinced it utterly necessary. Basically, everyone in society would have to understand the danger and recognize the solution months or years before the attempt to quarantine a city even took place.

how long would it take to get into place?

Figure two weeks minimum to have enough personnel and equipment to seal off New York City. That's assuming they've planned and trained for the eventuality. If not, then anywhere form 30 days to never.

In the US, the military is based in overwhelmingly in the Southwest. Only the National Guard is local. The Guard takes 72 hours for first deployment and then up to a week for secondary. Deploying the army from the Southwest would take up to two weeks. Remember, its not just the troops but the entire military infrastructure you have to move. The kill zones will require air power which will have to be shifted from the Southwest as well. Shifting air power means more than just flying planes around, it means moving the ground crews and all the equipment of an airfield as well.

The military appears to move fast in many situations because they do threat analysis and planning years in advance. Then they train on deploying against this or that threat. If they have a plan in place they can move pretty fast but not Hollywood fast.

(In the movie Cloverfield, the Army shows up within a couple of hours of the monster. Wouldn't happen.)

If you know a lot of people in the military you will hear about canceled leaves, new assignments and unit movements that clearly get them ready to head for some trouble spot. All this usually happens before any political leader even muses about sending troops anywhere. For example, I know the US army was preparing for almost a month to possibly go to Africa before anyone publicly discussed it. This happens all the time and most of the time, they don't deploy, but they're always planning and preparing to do so in case they need to. From the outside, it looks like the military moves in a few days but behind the scenes, they've been in motion for couple of weeks.

To my knowledge the US military has no serious plans for responding to a disease outbreak requiring quarantine and certainly nothing requiring massive lethal force. They certainly haven't trained for it. They would have to improvise and likely couldn't in time, largely because the task itself if nigh impossible.

let's talk about politics and legality too... there's no way this could be accomplished without resistance, what are the legal issues,

Legally, health authorities can still forcibly isolate infectious individuals as they did up through the 1950s but they will seldom do so today because of public outcry (see below.) At the start of an an outbreak there would be a lot of legal thrashing with authorities not using their powers. Later as thing deteriorated, martial law would shut down the debate. A state of emergency or martial law effectively suspends all law save military discipline. The executive powers, governors and the president are left to act largely arbitrarily as they see fit.

The courts have repeatedly validated the executives traditional authority to act outside or without the law in emergencies.

Historically, those in the executive have moved to address novel threats on their own authority and let the surviving lawyers rationalize it all later. That has happened a lot in foreign military and covert affairs but would apply to this scenario.

who would be in charge (FEMA?)

FEMA would play a role, they do game for disease outbreaks and at least once the trainers sprung a zombie scenario on them just to keep them on their toes. But FEMA major focus is on providing communication infrastructure during disasters for local leaders and responders and organizing financial assistance afterwards. It's a small organization with less than 10,000 people, mostly bureaucrats.

Disaster response in the US is actually the primary responsibility of state governments with most of the leg work done by the state National Guards. We're to big and diverse to handle it any other way.

how long would the debate delay action?

Fatally. I can't see us responding to any such crisis with any alacrity.

The moralizing over the ebola outbreak doesn't inspire confidence. I think far to many people see disasters and disease outbreaks as stages to flaunt their own imagined moral superiority instead of trying to save lives even if that hurts someone's feelings. For example, a lot of people hyperventilate on the supposed bigoted evil of precautionary quarantining of individuals coming from areas known to have active outbreaks even though such quarantines have over a century of proven effectiveness behind them.

Basically anyone who tries to move aggressively to contain a disease by inconveniencing people who might not be infectious, faces automatic knee jerk opposition from a powerful political segment. Those who like to bully others by pretending to be more-compassionate-than-thou will block any harsh measures that might be necessary until it is to late.

I saw that happen small scale in the early days of the AIDS epidemic back in the 80s. In one famous instance certain people freaked when medical personnel in San Francisco began wearing latex gloves whenever they dealt with patients. Standard procedure today, but back then it caused a lot of gnashing of teeth. There were protest, some minor violence and vandalism, and medical directors called before politicians to give accountings. That was just one of many episodes that delayed responses to the that horrific outbreak. A lot of people died needlessly because of those more interested in moralizing than saving lives.

Now imagine trying to get those people to even consider possibly contemplating giving a warning that at sometime in the future the military might threaten to shoot someone carrying a zombie virus out of New York.

We'll all have our brains eaten first.


There is one big question here. Do the people inside the city accept their fate and sit tight or do they try to escape?

Unless they felt like they had a real chance to survive by staying the urge to flee would be overwhelming. You can expect massive crowds all fleeing the city by whatever means they can. Road blocks would be overwhelmed, people would be trekking cross-country and flooding out of the city using every means they can.

In that situation it would be virtually impossible to quarantine the city. You have millions of people all desperate to get out. Even if you convinced troops to use deadly force and placed them in a ring around the city you would have to get them in position extremely fast and you would have a lot of trouble convincing them to fire on fleeing civilians.


Typically police and army will put up barricades at all roads in and out of the city plus a perimeter that evolves as the isolation lasts longer. Real life example of a perimeter can be the wall of Berlin. The roadblocks can be put in in a day (big roads first) the perimeter will take longer.

Don't forget that you need supplies for the survivors like food and clothing. That will be brought in by the people controlling the perimeter through a checkpoint and rationed out.

  • $\begingroup$ What's the point of keeping survivors in a zombie-infested area alive as soon as the area is quarantined? They aren't allowed to get out so the chances of survival are slim anyway. $\endgroup$
    – Mast
    Commented Oct 12, 2014 at 15:27

This is just a short answer to address the latter part of your question.

I highly doubt the authorities would be able to effectively contain it in the cities you mentioned. New York has the East River and the Hudson River; Chicago has Lake Michigan; Pittsburgh has the Allegheny and Monongahela Rivers, which become the Ohio River. It wouldn't be hard for a zombie or two to clamber into a dinghy from one of the docks and break the quarantine. The good thing about NYC being surrounded by rivers is that you could simply block off all the bridges to stop anyone from leaving Manhattan by land (and therefore by airports), but the other boroughs (okay, sans Staten Island) could not be quarantined like this.

Add to that the airports around the cities (JFK, LaGuardia, Pittsburgh International, Arnold Palmer Regional, O'Hare, and Midway International, as well as Newark International right outside NYC) and you have a number of different ways for zombies to avoid land barricades.

This is the additional stuff that makes the short answer a long answer.

So what do you do? Block off the roads, certainly. Like I said above, that may not be much use, but it will help a little. Without going into a months-long multi-billion-dollar defense program, you don't have a lot of options for destroying zombies, but perhaps you could modify existing weapons and send in troops to destroy the zombies. And if you're really stuck and have given up to losing the entire city, my advice would just be to demolish it. The whole thing. If you're going to lose all the people inside, you might as well contain the problem by destroying it.

Ahh, politics. Now we're in trouble. The outbreak will spread reasonably quickly. I would assume the government would have the legal right to go in and treat the zombies as hostile forces, but a) that would require a lot of effort and b) you'll have a lot of lawsuits if someone talks about how a soldier shot a grandmother (despite the fact that the grandmother was a zombie at the time). Shooting first and hiring lawyers later could solve the problem, but that will add a lot of legal battles to the whole mess. Shooting civilian zombies is a real grey area at the moment. And yes, FEMA would be up to their necks in stuff to do (and funding, hopefully).

So I think the government would be able to have the president designate the zombies as hostile forces and then go in and destroy them. To heck with the lawsuits. The passive route involves letting the city go to heck, while the active route involves either destroying the zombies to let the people inside survive or destroying the whole city to let the rest of the world live. Not a lot of legal precedent for that.


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