# Create a disease that can easily be cured by adopting a custom from another culture

I have a world with nations with culture/magic tied to each element. The Fire Nation was in the middle of invading the Earth nation when a disease starts to spread rapidly through their nation weakening it's people and indirectly putting a halt to their invasion. The disease doesn't seem to affect the other nations nearly as badly, despite originating in Earth, leading to the commonly claim that it is a punishment from god sent to stop the invasion and only able to affect Fire and 'unworthy' citizens.

My intent is for the disease to be a normal non-magical disease, and to be eventually cured by a protagonist, call him Bob. The disease affects Fire so much worse because the other nations have protections against the disease that Fire lacks. Water has healing magic to cure the disease and Air is too well isolated to have every been exposed to it. More importantly I would like Earth citizens to have some aspect of their lifestyle or culture that coincidentally protects them from the disease.

I'm looking for a believable disease that can be thwarted by something Earth citizens usually do, and which Fire can adopt quickly to stop the spread of the disease and ideally help those already sick to recover from it.

Bob is trained in medicine, herbs, and mundane healing, plus having a bit more scientific view to medicine in a world where people tend to believe more in magic and mysticism. He also has learned Water's magical healing. Few know both healing styles and previous hostilities mean there are no other Water healers willing to help Fire. Water magic also helps him 'sense' illness, which he can use to identify what mundane treatments to use when medicine will work better then magic. He has spent some weeks/months traveling & healing individuals using his Water magic already and has a good familiarity with the disease when he ends up in a Earth city currently occupied by Fire where the disease is currently spreading to Fire, but few Earth, citizens. He also notices that the few Fire citizens who have started to adopt Earth customs also seem less affected by the disease

Curious why this is tries to figure out what is protecting Earth in hopes of discovering a non-magical cure. I want him to be able to figure out something that would work within a relatively short time (say few months at max, sooner the better).

To help justify why he can do it so quickly when other's haven't I thought he would be aided by the combination of scientific medicine with Water magic allowing him to more thoroughly 'sense' differences between Earth/Fire/Sick/Healthy citizens to identify what is different, along with most citizens accepting the divine explanation and thus not looking for a mundane cure. The disease is also only been a problem for a little while, say 5-8 months by the time he cures it, so there hasn't been that much time to discover a cure. Still, justifying why he is able to find a solution so fast without someone else stumbling upon it would be great!

While I doubt I'll get everything Ideally I'd like a disease and cure that fit as many criteria as possible:

• Scientifically believable to exist
• the disease doesn't kill very fast, but renders one so weak they struggle to do daily tasks and is not quickly recovered from
• The cure can help those already infected recover, not just prevent new infections.
• cure can be discovered fast by Bob but not be so obvious someone else should have guessed it.
• Fire can adopt the cure quickly such that they can be back up to something close to fighting strength in a reasonable quick time, again a few months,
• The common peasants of Fire can benefit from this cure even if Fire's government puts little effort into helping them, ie not a large logistical overhead to enacting it.
• Doesn't draw the attention of Fire's leaders to Bob, who he's hiding from, Fire citizens often are willing not to report the guy helping them.

My original idea was that there is a staple food item of Earth that happens to provide some nutrient or even bacteria that helps fight off the disease (think a yogurt grown from a bacteria with some antibacterial property particularly effective against the disease?). My biggest issue with the idea is the logistics of it, It's likely the food would have to be stolen from Earth to get enough to treat Fire's citizens, and with limited supplies of food this means starving Earth and Fire likely only bothering to get the cure to the rich and military and not to the peasants that Bob is actually most interested in curing. I don't think Bob would reveal the secret if he knew it wouldn't help the common man and would lead to more war and starvation for Earth citizens. If the food stuffs was something that wasn't hard to get hold of in sufficient quantity to cure folks without Fire's stealing the food that would work, but why would Fire have enough in it's own borders to treat everyone but not have poor citizens already eating it?

• Does adopting the custom to separate drinking water from effluent water count? When people adopted this custom in the late 19th century lots of diseases vanished as if swept away. And modern people understood why those idiotic Romans spent so much effort and treasure on aqueducts and sewers. – AlexP May 12 '17 at 21:34
• Could this be as simple as a disease that presents with sores on the lips (plus other symptoms you list) and is only transmittable by touch. Fire nations greeting of a kiss on both cheeks is responsbile for transmission and they adopt the water nations traditional hand shake greeting instead? Or are you looking for more complex? – Twelfth May 12 '17 at 23:14
• The Fire Nation was in the middle of invading the Earth nation This sounds familiar... (Bob , the Last Disease Bender) – atakanyenel May 13 '17 at 9:26
• Adopting a custom: washing hands – theonlygusti May 13 '17 at 11:16
• Drinking tea and never drinking unboiled water. – Ian Ringrose May 13 '17 at 18:40

Necator americanus (Hookworm) and latrines.

Up until the early 1900s, people in the Southern United States would just go #2 by going out to the field and squatting. The problem is that there are parasites, namely hookworm, that can crawl out of old poo and reinfect people by burrowing into their feet when they go out to the same area, to poop again or maybe do some farm work. This is why using "night-soil" as fertilizer is an extremely bad idea. While a few hookworms aren't that bad, too many can cause:

• severe lethargy
• nausea
• loss of appetite
• diarrhea
• abdominal pain

Enter the solution: a pit latrine. Dig a hole deep enough so the hookworms can't find another foot to invade before they die, and problem solved. There's a Radiolab piece on it.

For your point where you want the disease to clear quickly, hookworms have a months-to-years-long residency in the body, but there are other soil-transmitted diseases. Or your hookworm could just have quicker turnover. Also, in your Fire Nation, maybe they could burn/boil/heat (sterilize/pasteurize) their poop if they really wanted to use it as fertilizer. Maybe there's a zoonotic parasite present in other animals' poo that could cause a more transient infection and where there's more of a reason to reuse the manure as fertilizer. Maybe just in an animal that the Fire Nation uses as a beast of burden/livestock?

• This is actually a huge problem in India right now. youtube.com/watch?v=V35Vw29tay0 Their Caste system made it super taboo to have people empty their latrines. So now, nobody wants to do it anymore, so there is a huge open defecation problem in India which leads to many of their children dying. – Stephan Branczyk May 16 '17 at 1:41

# Smoking.

This was the plot of a science fiction story back in one of the pulps during (I estimate) the early 60s.

In this case, the organism is a slow-multiplying pneumococcus bacterium which itself is essentially a minute partly-magical parasite which is stimulated by excess levels of fire magic, which obviously appear in the bodies of the Fire nation. Smoking works because smoke is the byproduct of fire, and so tends to absorb Fire energy, essentially smothering the parasite. Tobacco exists in the Fire nation, but smoking has never taken hold since in the long run it is extremely injurious to the Fire nation inhabitants. But it works more quickly on the parasite than on people, so smoking kills it and then the patient stops smoking. The whole process is similar to chemotherapy, whose agents are themselves toxic, only more to cancer cells than to others.

The effect was noted when earth POWs were allowed to smoke, and in the process some of their guards were seen to come down with the disease but then, in defiance of all experience, recovered.

Even better, the guards were assigned to be guards because they were in early stages of the disease's debilitation and not suited for more strenuous duties. Guard duty is not physically demanding, so affected soldiers could perform the duty for a while. Then, of course, they started recovering. Bob was part of the guard unit, but was the only one to make the connection.

With the collapse of the invasion, the influx of earth POWs has ceased. With no new POWs bringing cigarettes the POW population has had to quit cold-turkey. So the cures were only a transient phenomenon, and the government is in the dark about what smoking can do. This gives Bob the position of being the only one who has figured it out.

• Great answer. I started to read it and immediately thought, wait, this is chemotherapy! – Robert Columbia May 12 '17 at 23:55
• I took out your edit marks, since they aren't really necessary. – kingledion May 13 '17 at 19:14

Scurvy

from Lind's A treatise on the scurvy.

The following relation is no less curious. A sailor in the Greenland ships was so over- run and disabled with the scurvy, that his companions put him into a boat, and sent him on shore ; leaving him there to perish, without the least expediation of a recovery. The poor wretch had quite lost the use of his limbs -, he could only crawl about on the ground. This he found covered with a plant, which he, continually grasing like a beast of the field, plucked up with his teeth. In a short time he was by this means perfedtly re- covered 'y and, upon his returning home, it was found to be the herb scurvygrass.

This is a disease that meets all your criteria. The question: why did Fire people not suffer from scurvy before this event? The answer: they did, but it got worse. Mild scurvy was probably endemic in winter months in Northern Europe. Your fire people could be indifferent to vegetables most of the time but then during the war got away from greens and vegetables entirely, and so came down with the scurvy. You can die of scurvy but you can also bounce back fast.

Nutritional diseases were hard for people back in those days. They were mixed in with lots of other diseases. Pellagra is another great example: maize is a wonderful crop but once the Italians began living on it they developed rampant pellagra. I read an account of a mid 19th century Mexican scientist who attending a meeting on pellagra. He pointed out that the Italians were preparing their maize incorrectly: it should be mixed with lime. Of course he was roundly ignored. But that is why the Mexicans did not get pellagra over the centuries they lived on maize - lime releases the niacin.

• I actually really love the simplicity of this answer and I know it's happened, actually multuple times. Even after 'curying' scruvy in the navies they had epidemics a few times because they didn't understand why lemon would help and tried mixing in different fruits or used fruits cured in such a way as to loose the vitamins they needed so it could easily work. It's almost too easy that it feels like cheating. Only real issue I have is that it's hard for Water magic to treat it (and not notice it's a nutritional issue rather then usual disease) based off of how I imagine Water healing. – dsollen May 15 '17 at 13:16
• +1 This is the best answer, because a nutrient deficiency (can be very debilitating) is most easily explained by diet. There could be foods on the home planet that supplied the protein/mineral/vitamin where the earth analogue in flavor/consistency/type did not. Thus, the culture would need to adopt new foods from other cultures to replace what is missing. – Stephen Ruhl May 15 '17 at 15:36
• @dsollen I scrolled down to see that no-one had not answered Scurvy yet. This would be my answer. To expand on it: compare this to real life seafaring conquerors. Their food supplies would not contain foodstuffs that had ascorbic acid (Vitamin C) in it. Hence they got scurvy once they were removed from the food-supplies of their home nations. But when they arrived in the foreign location they were meant to be conquering, they could eat — to them — foreign food that did have ascorbic acid, such as lime. – MichaelK Sep 12 '17 at 11:12
• @MichaelK I really liked the scurvy answer. My biggest complaint was explaining why it suddenly 'struck' all at once, so it looked like a contagious disease. Your answer partially addresses that, except I also want the disease to infect the peasants within the Fire Nation itself, who wouldn't have had a change in their diet. If I had an actually contagious disease which could be combated by fixing a vitamin deficiency, by changing how food is prepared to address that deficiency, that would be ideal. – dsollen Sep 12 '17 at 13:53
• @dsollen Also scurvy is an excellent story-disease, precisely because of its symptoms. Casually speaking your body dies slowly as if you are a very slowly decomposing corpse. In actuality what happens is that cells have reached their end-of-life are normally replaced by new cells. What scurvy does is that these new cells cannot be built because the collagen that is supposed to give them strength melts at normal body temperature when you are afflicted by scurvy. Also scurvy is a protracted and progressive disease which makes the outbreak time hard to pin down anyway. – MichaelK Sep 12 '17 at 14:02

Kosher food practices.

For example, the disease is spread by eating the meet of the smerp. The Earth Nation's religion forbids eating this animal, but the Fire Nation has no such prohibition.

• This works because water and air may not be able to farm this animal – Cameron Leary May 14 '17 at 17:26
• This one might be a little too obvious. If only the non-religious get sick, this one will be figured out quickly, and then everyone will realize that the smerp is dangerous and stop eating it all-together. – Erik May 16 '17 at 9:31
• There is evidence that the geographic areas covered by particular food taboos are much smaller in places where the germ load is high than in places where the germ load is low. if everyone has different food taboos, some of them will survive when their taboo prevents diseases that other cultures do not inhibit with taboos. This is also likely a source of the practice of circumcision (or at least a reason that cultures that had it in places where they prevented disease spread were more selectively fit). – ohwilleke May 17 '17 at 0:45

For an interesting and quite possibly real example (though of prevention rather than cure), see Voltaire's Letter on smallpox: http://www.bartleby.com/34/2/11.html

The Circassian women have, from time immemorial, communicated the small-pox to their children when not above six months old by making an incision in the arm, and by putting into this incision a pustule, taken carefully from the body of another child.

In order, therefore, to preserve the life and beauty of their children, the only thing remaining was to give them the small-pox in their infant years. This they did by inoculating in the body of a child a pustule taken from the most regular and at the same time the most favourable sort of small-pox that could be procured. ... The Turks, who are people of good sense, soon adopted this custom, insomuch that at this time there is not a bassa in Constantinople but communicates the small-pox to his children of both sexes immediately upon their being weaned.

Washing hands. Seriously. As fire people, they might minimize contact with water through cultural taboo. Washing hands is a very serious anti-microbe WMD. But what seems obvious to us today took until the mid 1800s to be understood. Ignaz Semmelweis noticed a pattern of dying vs. surviving in hospitals that made him finally see the connection.

One thing that you may want to have is different methods of water purification. Historically communities purified water by turning into a weak form of booze making it safe to drink. However you could have it since most people (and especially troops) of the fire nation have the ability to summon fire literally at their finger tips they ban most forms of alcohol from their fire mage who are in turn supposed to boil their water to make it safe to drink.

Then all you need is some form of disease, fungus, parasite, or other pathogen that exists primarily in the earth nation that can survive being boiling for the amount of time people usually boil their water.

A good way of showing this in the culture is the earth nation could think that tea, coffee, and other drinks where you boil water are terrible for your health and drink only booze as it is the "healthy" and "natural" option

Edit

After reading the comments and looking into it a bit more I realized having the entire earth nation drink only their preferred form of alcohol may not be viable however I have two more options

Option 1

The earth kingdom believes all rivers and lakes to be cursed (probably because drinking from them will make them sick more often than not) and as such think only water given to them from the earth is safe. So even though they may have rivers and lakes nearby they drink exclusively from wells and aqueducts that come from either underground springs or mountain ice melts (both of which may be considered sacred by the earth nation). This is made practical by the fact that digging a well for the earth kingdom is not a multi day endeavor with multiple people digging with shovels you just need one moderately powerful earth mage to think really hard for an afternoon and then you have a new well. Since digging many wells quickly is not viable for the fire nation they will tend to either disregard the earth nations superstition and drink from the perfectly good rivers and lakes or drink from the earth nation wells if wherever they conquer doesn't destroy or poison the wells.

Option 2

This still goes with the earth nation believing that rivers and lakes are cursed. They will take the time to do a ritual to ask the earth god( if you have one) to remove the curse by running the water through a sand filter https://en.wikipedia.org/wiki/Sand_filter This filter will obviously be crude in many cases and there will probably be an industry of selling better filters than one can make at home as better filters = better curse breaking ability. As the filters can be seen as a strange cultural thing it would be easy for the fire nation to ignore this as part of the local superstition since large towns and cities would likely still be supplied by wells and aqueducts. Also I think where they get sand from can generally be hand waved as earth mages can just make sand out of rocks or clean the sand filters.

Out of all three of my ideas you can mix and match them since they are not mutually exclusive, so people may prefer to drink beer made of water from a holy mountain that was filtered through the grand filter in the church.

• I admit I was ready to dismiss this as impractical as most of my hygiene/sanitation ideas were as soon as you said purification. However, I think generally there is a good idea here, that hits many of the points I mentioned. The reason it wasn't discovered faster is obvious here, Fire thought their sanitation method was better so why 'downgrade' to a worse method. The question of how the disease spread so fast comes to mind if it spreads via water, the obvious answer is involves bad sanitation and fecal water, but it shouldn't spread as fast. Still I'll think on it but It may work. – dsollen May 12 '17 at 22:13
• To explain why the discovery can cure people already infected I think something along the lines of constant re-infection (and high mutation rate) might work. The body is adapting and driving off the parasite/disease but if everyone is uh...contaminating the water then they are constantly re-infecting themselves. Once people stop being infected their bodies can drive off the current strain relatively fast? Not sure it's realistic though? I'd almost have to combine it with @William.c suggestion of an evolved partial resistance in Earth though, can't realistically claim they only drink beer : – dsollen May 12 '17 at 22:19
• Thanks for the update, it does help a bit. At first glance it doesn't explain why Fire citizens in Earth cities would get sick, as they presumably would use pre-build wells in those cities, but I could probably handwave that a little. My biggest issue seems to be that these sort of natural occuring bacteria/parasites in water the human body usually develops an immunity to quickly so claiming that it keep them sick for so long (and wasn't due to parasite in the body that continues to hurt after infection) seems unrealistic. I am still seriously considering this though. – dsollen May 15 '17 at 13:23
• One thing you may want to consider is spending on what is actually getting people sick it may be able to contaminate wells so in cities handfuls of wells will still get you sick, but the earth kingdom people either use it for wash water or filter it before drinking so they may not notice. The fire kingdom as a whole might think that these "cursed" wells are pure superstition where as grunts that take advice from the earth kingdom residents get sick less while in cities. But you may also get earth kingdom peasants passive aggressively suggesting bad wells to fire nation troops – SilverShadow May 15 '17 at 15:28
• I know this old, but I have to say: It probably makes more sense for the problem to be an inorganic toxin like lead or mercury, which can't be removed with boiling (unless you properly distill) but can be removed with filters. Of course, simple sand filters won't work in this case, but charcoal ones should. – No Name Nov 14 '17 at 4:04

Make the disease the Bubonic plague and have Earth keep cats in their households. The cats eat the rats that host the fleas that carry the plague.

This doesn't cure the plague but it prevents it in Earth cities. Earth citizens would then not be too keen on visiting other lands since they can and would catch the plague in cities without cats. They may bring the plague back with them but it wouldn't spread very far.

• If you're really going to claim that 15th century Europeans did not keep cats, you should provide a link to a source. Or, to be more blunt, this is a bogus post. – WhatRoughBeast May 13 '17 at 20:26
• The main theory on how the bubonic plague spread was that infected FLEAS rode on the rats and then transmitted it to humans. Cats would help spread this because they would get the fleas. (Follow the link and go to cause for evidence) link – Cameron Leary May 14 '17 at 0:29
• On the other hand, there are diseases that are spread by mice and rats. So change the disease from bubonic plague to hantavirus, and you're set. – Peter Shor May 14 '17 at 13:34
• @WhatRoughBeast As I understand it part of the problem was that the Europeans started to blame cats for the plauge due to superstition, especial black 'familiar' cats, driving them away and making the threat larger. Not sure cats alone would help with that plague, but the concept of some disease I invent that cats could combat the disease vectors is viable even if it's not quite the same as Bubonic plauge, which it wouldn't be as I want a less lethal, more debilitating, disease anyways. Though I can't help noticing it's a shadowCat suggesting cats are the cure. Cats stick together :P – dsollen May 15 '17 at 13:29
• Offering an alternative to the cats proposal, bubonic plague WAS able to be stymied by more frequent bathing; a practise common with the European Jews, but uncommon with others in the region at the time- Look at the spread of the plague and the population data of most nations, vs Poland (who was largely untouched by the plague, though also due to having much lower population density the major towns/cites) – Shane Gadsby May 16 '17 at 0:01

# Burial Practices

The fire people practice funerary cannibalism, and are therefore susceptible to Kuru, a slow disease that is transmitted by consumption of the brain.

The Fire nation believes that, just as all fire proceeds from fire, so all life proceeds from life. When somebody dies, their fire goes out, just as an untended flame will wither and die. But, just as two flames brought together will burn as one, so two people, brought together into the same body, will burn together. After a person's flame has gone out, but before the embers have died down, the community gathers to honor them. Each person eats part of the deceased, taking their flame. This way, so long as the community survives, the flames of the ancestors will never go out.

The Earth people believe that life proceeds from the ground, and returns to the ground to grow again. This is seen in the daily cycle of eating meals from the ground, followed by defecation into the ground. It is also seen in the cycle of a life, where each child learns first to walk, then to run, but will eventually return to the ground. When an Earth person dies, they are buried, that the strength that they borrowed from the earth may rest, and return to strengthen future generations.

• I like this :-) Cremation + Scattering for the Air people and burial at sea for the water people (or putrifaction/liquidification) – HomoTechsual May 14 '17 at 16:20
• Depending on exactly where the air people live, sky burial (en.wikipedia.org/wiki/Sky_burial) may be more practical than cremation. Either way fits quite nicely. – Eldritch Cheese May 14 '17 at 17:16
• LOL, I asked a question about ritual canabilism with Kuru being the main thing everyone brought up before ;). It's a good idea, but I'm afraid I've already done enough world building for the nations that I can't use this, Fire uses cremation via fire magic for their dead, so their the least likely to have problems with disease spread after death. A good answer giving only the details in the original question though, so up voting :) – dsollen May 15 '17 at 13:32

How about introducing the malaria mosquito? To keep your own protected, the cultural habit of drinking tonic water (with or without the gin) You could keep the ingredient quinine or more probably, the source of the quinine a state secret.

• "It is a curious fact, and one to which no-one knows quite how much importance to attach, that something like 85 percent of all known worlds in the Galaxy, be they primitive or highly advanced, have invented a drink called jynnan tonyx, or gee-N'N-T'N-ix, or jinond-o-nicks, or any one of a thousand variations on this phonetic theme." – ivanivan May 13 '17 at 1:00
• Or magically fortified Tobasco sauce. Any mosquitoes that bite someone who has imbibed enough of this sauce will drink up, fly off, and promptly explode. – Jasper May 13 '17 at 5:59
• @Jasper are you sure that's not a pan-galactic gargle blaster? – jwenting May 15 '17 at 7:32
• This is, literally, THE answer. I lament the inadequacy of the single up-vote I have to give, but give it I do. – Grimm The Opiner May 15 '17 at 8:35

Actual real world example: Beriberi in countries where white rice is eaten, especially 19th century Japan.

White rice is deficient in vitamin B1 and there was a cultural belief that cheaper cereals were for the poor. The upper classes did develop beriberi but the traditional dietary cures were discarded when Western medicine became known and people started to believe that it was caused by bacteria.

Realistically, you could make it a combination of practices that give the Earth people an advantage over the Fire people.

Say the disease in question is similar to giardiasis, a parasitic infection of the intestine acquired from contaminated water and fecal matter, which can also be spread directly between people. The Earth people could be protected by:

• Acquired resistance;

• Drinking tea, which is rendered safe by boiling;

• Religious cleanliness rituals; and

• Eating foods seasoned with herbs that combat the disease. (I’ve read claims that in real life this includes garlic and long pepper, but I can’t speak to their accuracy, so you could just invent something.)

• Running out of beer (also rendered safe by boiling, and alcohol to a lesser extent) and switching to contaminated sources;

• Poor hygiene practices in the field, such as infrequent bathing or lack of latrines;

• Not using the aforementioned healing herbs in their food; and

• Suffering from nutrient deficiency, or using other recreational drugs (liquor, something like amphetamine) that suppress the immune system, making them more vulnerable to infection.

You could also make the parasite common only in Earth territory, for example due to different climate. So it mainly affects the invaders because they’re invaders—ordinary Fire people are perhaps more vulnerable than ordinary Earth people, but it’s mainly the logistics of army life that cause the outbreak. And they can be cured by adopting Earth people customs: taking herbs that treat the disease, and improving sanitation and diet to prevent it.

# Cholera

This disease ravaged Europe in the 19th century. Its main symptoms are severe diarrhea, vomitting and stomach pain. It does not have a high mortality rate (less than 10%), but the way it affects people can be terrifying : through extreme dehydration, a strong and healthy man can be transformed into a living ghost only in a few hours, unable to do anything but lie in bed.

The disease usually comes from contaminated water, for exemple a well dug right next to a septic tank (see Broad street pump cholera outbreak). You can imagine that Earth nation has one or several of the followings to prevent the disease (chose the ones that fit your story the best) :

1. Sacred places to drink water from, not located inside the cities
2. proper sanitation system, with sewers and/or aqueduc to bring clean water
3. Some sort of national booze like SilverShdow suggested. I wouldn't be surprised this was a comon thing in Antiquity or in the Middle-Ages.
4. Some sort of National boiled beuverage like thea.
5. Garlic. You may have to make some additional research on this, but garlic usually helps against all sorts of infections (I tested it on several occasions).
6. Burning bodies. It always helps a lot against all sorts of illness. Especially if the fire nation use to honor the dead for a few days before burrying it.

None of these solutions can cure the disease, they just prevent it. One way to help the ill is to make them drink lots of water and something countaining sodium, like salt. Maybe your hero can make this discover shortly before/after realising that the disease comes from water.

If not taken care of, such a disease can spread rapidly : one infected well or pound can affect hundreds of persons. I don't know how long it lasts, but you can make it long enough so a significant portion of the army and the people is ill at the same time, and the rest too busy caring for the dead and the dying to actually help for the war effort.

Once the source of the Cholera discovered, people can just stop drinking water from where they poop (or the other way around), or produce high quantity of booze/thea/garlic/whatever. Then, with almost no new case to deal with, the number of sick fire guys decreases, allowing the army to march again, despite being weakened.

I know you are asking for a disease but simply having a parasite that Fire, Earth, and Water all encounter and simply making the other two nations resistant too seems like a better idea. It's realistic and wouldn't be discovered very quickly.

To add resistance there could be a substance in the food the other nations eat. For example, not a ton of people eat rice in the U.S. but it is a staple food in Asia. So while rice may not be the cure, a crop that has a substance that is debilitating to the parasites that is cheap to make once you have the seeds for it might be a good option.

• It would help the spreading and resistance very well. but how does one cure it? If it requires building an immunity to resist there isn't much that can be done by Bob unless he discovers germ theory and something like boiling water which I'm hesitant to do because it's hard to discover so fast by Bob and would change the world so drastically if understood. – dsollen May 12 '17 at 21:47

Fire people eat black rye bread. I'd expect fire land to be a dry place and fire people not to know about ergot. But in the moister earth soils, fire cultivation methods will make the ergot thrive.

When they started to seize the earth plains, the fire guys started farming them with cheap labor (exactly as Romans did when they conquered Sicily) and send the crop to feed their army and cities. They won’t use crop rotation and they won’t double-check their crops for fungi. The downside is, it needs at least one year after the invasion for the epidemic to start, maybe more. Basically, the harvest just after the foreboding unexpectedly strong rain season. Good point is, it won’t be traced back, as the flour will be sent to be sold in the capital and mixed with non-contaminated one before getting sent back to the soldiers. And who would expect honest fire peasants cultivating rye, as they have always done, to be the culprits? (In the real world, it took them centuries to find it out.)

Another good point is, the more you’re involved with the invasion (being a soldier, buying goods from invaded lands), the more chances are there you’ll be eating contaminated bread, without this being a specific rule.

Earth people are pretty much immune to ergotism, they eat white wheat bread, the whiter the better. Just make Bob stumble upon a sack of contaminated wheat, discarded because it's not white enough.

For something of an Earth flavor... salt. Fire Nation treats it as a luxury; Earth Nation treats it as a staple of cooking. With salt, lots of bacterial spread is retarded. Adding salt won't cure those already sick but will slow spread for bacteria.

• Since salt is an essential nutrient, and lack of salt will eventually kill you, this isn't a very realistic solution. Maybe use some other spice. – Peter Shor May 13 '17 at 23:12
• You can get enough salt in diet to live from just eating meat, dairy, eggs, and fish. Some vegetables also contain salt. That salt, however, is not enough to control spoilage or limit pests. @PeterShor – SRM May 14 '17 at 1:51
• That's only if you have lots of meat to eat. The British salt tax in India meant that poor people couldn't afford enough salt, and it led to millions of deaths. – Peter Shor May 14 '17 at 2:18
• @PeterShor What's your point? If the culture this author is creating has enough dietary salt, then it's perfectly valid to use excess salt as the cultural ingredient to stave off disease... exactly my answer. – SRM May 14 '17 at 12:55

Two examples come to mind:

1) malaria -- recurring disease that often does not kill but makes person very weak. The earliest cure (quinine) was discovered by Jesuits based on observation of indigenous people making concoction from bark of cinchona tree. Cultural habits that could be adopted from other culture would be sleeping under nets and adopting ritual of drinking tea from tree bark.

2) AIDS -- caused by HIV, does not kill fast, but it seems that circumcision greatly reduce the chances of disease transmission. This would lack the requirement of finding cure for already sick, but arguably, adopting cultural habits like circumcision and, for example, more prohibitive rules on sexual life would help to put the spread under control.

• circumcission does not prevent HIV infection, hygiene does. And of course sexual abstinence, so not having sex with potentially infected individuals. Strong cultural disgust at homosexual relations comes to mind, or better yet a culture that eschews completely sex outside of marriage (whatever form that marriage may take, group marriages are still possible as long as the members of the group stay faithful to the group). – jwenting May 15 '17 at 7:35
• Citing myself: "it seems that circumcision greatly reduce the chances of disease transmission", I never claimed "prevention". This view is supported by WHO: who.int/hiv/topics/malecircumcision/en – user61244 May 15 '17 at 15:04
• circumcission in itself prevents nothing. It MAY help maintain proper hygiene, but that's it. And I'm not sure I believe the WHO in this anyway, they're extremely politicised, as is all of the UN, and defending circumcission is certainly something that from a political/religious viewpoint is interesting, especially for Americans and Muslims (the only 2 major groups in the world doing it as standard on most all men, Jews being a far smaller group). If it were so good, HIV infection rates in Europe (where it is rarely done) would be far higher than in the US but they aren't... – jwenting May 16 '17 at 6:02
• About randomized trials: ncbi.nlm.nih.gov/pubmedhealth/PMH0012002 – user61244 May 16 '17 at 14:24
• Plus explanation why it works: ncbi.nlm.nih.gov/pmc/articles/PMC1127372 – user61244 May 16 '17 at 14:25

Filariasis

Fever is a pretty effective treatment for a lot of things, so much so that malaria has been used to treat leprosy and end-stage syphilis.

However, leprosy doesn't respond nearly as well to fever as filariasis does, according to this doctor again. Protracted fever in malaria patients causes a near-complete extinction of the parasites.

So perhaps the Earth Nation has a strong tradition of bathing in hot springs? Or volcanic mud baths, which is definitely a thing people do worldwide wherever there are hot mud pools. Thematically that makes sense, submerging yourself in the literal earth makes sense as a custom for an Earth Nation.

The Fire nation can take up building sweat lodges or something.

• I like this answer, it's nice and strightforward, can work for diseases, and most of all is absurldy easy for Fire citizens, even the poor, to emulate since they are Fire after all, creating sweat lodges isn't difficult. The biggest issue I see though is having Earth using hot springs, it seems like they would be too limited to ensure all of Earth had hotsprings close enough to make regular bathing, even for the peasants, an option. – dsollen May 15 '17 at 16:42
• Filariasis is mosquito-borne, so if you squint you could say that enough people bathe to give the Earth population herd immunity. Or their Earth connection could just draw hot rocks upwards? – Resonating May 15 '17 at 16:50

A disease that only affects some type of herds and transmits to humans

One of the main ideas behind religious and cultural prohibition of some meats in some cultures points back to eras in our past where those food inputs were either unhealthy, poisoned or dying with some kind of disease.

Why can't we eat Lord TwistedTail, mom? we're hungry. ~Because *insert god* says so, timmy.

It could as well be that the fire nation is the only nation that uses mass cow amounts as meat input to their weather conditions, and thus, the only one affected by A really interesting disease not long ago, in a galaxy not far, far away.

• Sometimes I half-joke that the reason that BSE is so much more a problem in Europe than America is that all the good farmers moved to America. If you aren't smart enough to realize that you can afford a farm double or even quadruple the size just by emigrating, you are probably that kind of person who wouldn't see any problem with feeding brains to your cattle. – Robert Columbia May 15 '17 at 13:08
• meh @RobertColumbia i live in a very big farming area in south europe, and there's good farmers in here, so we didn't had much affection. – CptEric May 15 '17 at 13:14

Obesity a disease that can be cured by taking healthy food habit and lifestyle available in the culture and gastronomy of some indigenous culture that lacks fast food, but focuses on natural food or spiritually awakening and nature friendly lifestyle.

• Interesting answer. If you could flesh it out a bit it would be more valuable. As it is now looks more like a comment. – L.Dutch - Reinstate Monica May 16 '17 at 4:35