October 5, 2021

Corona lessons from cholera: miasma theory vindicated over contagionism (mediated vs. person-to-person transmission)

I'm going to start corona-posting some more, but found it necessary to preface it with a look back on the history of modern epidemiology, from the 19th century, whose major concern was recurring pandemics of cholera.

The standard Reddit-tier take is that on one side was the miasma theory, which held that foul outdoor air contaminated by decaying organic matter was to blame for giving people cholera. Boo, hiss. On the other side -- oh hell yeah -- was the germ theory, which was eventually proven correct.

In reality those two theories are completely orthogonal to each other, and one neither discredits nor testifies to the other.

The germ theory is about causative agents, such as bacteria, viruses, and other pathogens -- as opposed to other things that could harm a person, like toxins, allergens, nutritional deficiency, and so on.

The miasma theory was about how a causative agent -- regardless of whatever it happened to be -- circulated throughout a population, spreading disease. Miasma theory relied on a medium (such as contaminated air) to transmit the causative agent from one person to another, indirectly. Its rival, contagion theory, held that transmission was through unmediated contact in close proximity (such as coughing in someone else's face).

To simplify things, we can talk about an "encounter" between a sick person and a healthy person. Miasma theory does not require such an encounter for transmission to occur, whereas contagion theory does. Miasma requires a medium, contagion does not.

We will get into how this changes a formal mathematical model of epidemic dynamics in a later post. But suffice it to say for now that the contagion model is the standard S-I-R model, tracking susceptible, infected, and recovered individuals, who have encounters with each other. Miasma requires a new variable to track, namely the concentration of the contaminant in the medium, as well as descriptions of how infected and susceptible individuals come into contact with that medium (their encounters with each other being irrelevant).

This is the actual substance of the actual debate that raged during an actual pandemic of an actual disease. Only clueless autists would ignore the historical context of the debate when trying to identify what the crux of the matter was, and what was incidental or irrelevant. It was about whether, for cholera in 19th-C. Europe, transmission was mediated or direct. That's all -- every other detail is secondary, tertiary, and further removed from the fundamental disagreement between the contagion vs. miasma camps.

Specifically, there is nothing relevant about air being the medium for the miasma camp -- air is only one of many potential media via which a causative agent could be transmitted indirectly from one person to another. Even if you assumed it was air, it's irrelevant that they thought it was outdoor air -- indoor air is still a medium for transmission. And it's irrelevant that they highlighted air of a foul odor -- neutral or pleasant-smelling air is still a medium for transmission.

And again, the causative agent question is totally independent -- miasma theory does not depend on decaying organic matter / vapors it gave off as the causative agent. That just happened to be the source they believed in. They could have believed in germs or bacteria in particular as the causative agent, and that would not have changed the nature of their disagreement with the contagionists, over whether that agent was transmitted through a medium or directly.

So in evaluating who won the debate, we look at the level where they actually disagreed, rather than consider every aspect of the theory together. The two camps disagreed at a very fundamental level, over direct vs. mediated transmission -- so we ignore any details that pertain to finer levels of specificity.

For example, it would take two miasma theorists to debate over whether it was air or some other medium, whether the air responsible came from outdoors or indoors, whether the air had to be foul or neutral-smelling, etc. That was not the debate, so we ignore those details of the theory in evaluating its performance against its rival, which denied that mediated transmission of any kind was taking place.

As it turns out, the miasma theory was decisively vindicated over the contagion theory. Cholera was transmitted through a contaminated material medium, whereby the initial sick person had no encounter whatsoever with the healthy people he would eventually infect.

At finer levels of specificity, the miasma proponents got the picture wrong. It was contaminated water, not air, that was the medium. And the initial contamination came not from outdoors, but indoors (a sick person's diarrhea, which then entered the sewers). They were right about the contaminated medium smelling foul, though.

But those details were not what they and their rivals were arguing over, so we ignore them in deciding which side won. The contagionists held that cholera was transmitted by a direct process similar to coughing in someone's face, or exchanging bodily fluids during sex. They were dead wrong -- cholera is a canonical example of mediated transmission, where the sick person and healthy person were not in the same room, building, or perhaps even block or neighborhood at the same time.

* * *

The victory of the miasmists doesn't end at the level of pure understanding, though, but continues through to the applied / solutions level. If the contagionists had been correct, then some kind of isolation of a sick person would have had a major effect in breaking the chain of transmission. But if transmission is through a medium, then isolating people from people will not necessarily break transmission at all -- if the medium is left to connect people indirectly.

And sure enough, quarantines and keeping everybody in their own little homes did not stop cholera, since people were connected by a public water supply. Isolated sick people continued to excrete their waste into that water supply, and healthy people continued to come into contact with that water supply through pumps (for drinking, washing, etc.).

Notice that the miasmists were not autists who said, "OK then, just sever the links to the medium". That is the analogy to breaking the chain of transmission in the contagion model. Keep sick people from excreting into the water supply -- how? Tell every sick person, of whom there are legions during a pandemic, to build their own water supply? Or maybe tell the healthy people not to drink or wash from the water supply when an outbreak is taking place -- so what's the point of supplying the water then? And water is a necessity, not a luxury.

These links to the medium cannot be severed, and "isolation" from the contaminated medium was not the solution the miasmists hit on.

Rather, it was sanitation -- i.e., purifying the medium of the contaminants responsible for the disease (whether or not this process cleared out other contaminants, though hopefully it would). Maybe they would remain present in the medium, but either killed or neutralized of their disease-causing power. Maybe they could be removed from the medium altogether, by a filter or something. Maybe the medium could be replenished so quickly with fresh material that the concentration of the contaminant could never reach a high enough level to pose a serious risk to someone who came into contact with it.

In the case of contaminated water, they could at least separate the supplies of water carrying away waste vs. bringing water in for consumption. That seems to sever one of the links -- while the sick are still polluting a medium, the healthy do not consume from that medium, but from a separate source.

However this does not generalize to all media. Air, for example, cannot be channeled into two decoupled paths for bringing-in vs. taking-away. The air you exhale into, is going to be breathed in by someone else. Like water, air is a necessity, so there's no isolation strategy that will work, only sanitation.

Insect-borne diseases behave much like a miasma disease, where transmission is mediated by the insect, which bites a sick host and then bites a healthy target. The source and destination have no encounter, and could be miles away from each other at all times. Isolating one person from another would not stop the spread, only neutralizing the insect, isolating from the insect, etc. Unlike the above miasma diseases, contact with this medium is not a necessity -- you never want to get bitten by them. But then miasma theory never said that the medium was a necessity, only that there was such a medium rather than transmission through encounters between sick and healthy individuals.

And as it happens, the diseases which motivated miasma theory to begin with were all ones with mediated transmission -- bubonic plague (fleas), malaria (Italian for "bad air," mediated by mosquitoes, though), and cholera (water). Air as a contaminated medium is an even greater vindication of the theory, since it gets the medium correct as well -- but that will have to wait until discussion of the SARS-like diseases, and perhaps respiratory diseases more broadly.

The point is, miasma theorists were smart, not stupid -- they could tell their disease of interest wasn't transmitted by encounters between sick and healthy, but the particular medium was hard to discern. Fleas? Mosquitoes? Water? Air? I dunno, some shit like that, though -- we can tell that it does not spread through one person encountering another, and that isolating people does not stop the spread.

Contagion theory does apply to some diseases, although given how much the picture changes when you view air as a potentially contaminated medium, I'm putting all respiratory diseases on hold as examples of the contagion model. Sure, someone could cough in another person's face, but they could just as easily cough into an empty room, where the particles remain suspended as aerosols, and someone else comes in minutes or hours after the sick person has left the room altogether. That's mediated, not an encounter.

The only uncontroversial examples of the contagion model are sexually transmitted diseases -- can't pass those along without a direct-contact encounter between two people. Ditto for ones passed from a pregnant mother to her baby, non-genetically. But these are usually clear in their mode of transmission, so it doesn't take an insightful person to describe them with the contagion model.

It's clearly too late to reclaim the title of "miasma" theory non-ironically, due to the autistic rewriting and mystifying of what took place during the 19th-C. cholera pandemics in Europe. But I think "mediated transmission" is still OK, as long as it's clearly opposed to "contagion" or "person-to-person" models.


  1. The word "malaria" literally meant "bad air". And while it didn't spread directly person-to-person like and STD, isolating people from mosquitos (harder to do with the general population, more feasible with those already infected) does prevent spreading. The miasma theory resulted in things like plague doctors wearing masks with flowers in the nose to counteract bad smells. Germ theory explains why quarantines & border controls can block spread (malaria spreading without direct contact boosted miasma theory and caused people to reject such controls as superstitious & unscientific).

    John Snow was an enemy of the miasma theory. He didn't argue that cholera must spread person-to-person. Instead he shut off a water pump because he thought that was spreading it. He compared his theory to the known case of intestinal worms reproducing themselves in the intestine and inducing the evacuation of infectious material from there, while rejecting that it could be spread by the exhalations of sick people like fevers.

    The term "germ theory" didn't exist back then, nor during the time of Ignatz Semmelweiss. And the puerperal fever he tried to act against was not being spread by air or water or even mosquitos or fleas, but humans (specifically, the hands of doctors operating on corpses and then pregnant women).

    "Contagion" is how infected diseases spread, and this doesn't have to mean "person to person". There are lots of other species that can serve as reservoirs, but only if an infection spreads it to them. And a single infected individual can spread a pathogen from one place to another, even if every "medium" in that place had been perfectly clean before their arrival.

  2. Reddit brain on full display, including not reading what you sperg out about in comments.

    Post already says "malaria" is Italian for "bad air".

    Miasma and germ theory are orthogonal -- former dealing with transmission of causative agents, latter dealing with identification of causative agents.

    Miasma theory led to modern sanitation, not just silly plague doctor stuff. This is uncontroversial -- but you're just a Reddit-brainer who can't even skim a Wikipedia page. You're supposed to say that the miasma proponents were "right for the wrong reasons" by pushing for and implementing modern sanitation measures.

    And not only for better ventilation -- COVID-19 alert -- but for keeping people away from sewage. Miasmists thought it was the gaseous part of sewage that was pathogenic, rather than the solid or liquid part of it -- but who cares? They did the right thing, and made people a lot healthier.

    Plague doctor masks did not make the situation worse. Net, huge positive.

    John Snow decisively proved the miasma theory, because there is no such thing as a theory in isolation. There's a debate between two sides. In the 19th C cholera debate, it was contagion or mediation. People were not transmitting cholera from one to the next directly. They transmitted it at a great distance, between people who didn't even encounter each other.

    What Snow did was clarify which material medium was mediating transmission -- not argue for contagion, which he proved was not at work.

    Also, his solution was not a real solution. You can shut off a single water pump, and tell its users to find another one. How do you scale that up to the whole of a city, let alone nation or continent, to end a pandemic? You can't.

    Only spergs think he ended cholera with This One Weird Trick of shutting of a single pump. They had to purify the contaminated medium, and separate outgoing vs. ingoing water supplies.

    Semmelweiss reference is irrelevant, since we're talking about transmission of causative agents, not identifying which family they belong to (toxin, pathogen, etc.).

    "Contagion" means "with" "touch", same root as "tangible". Synonymous with "contact". As in, not mediated by something else -- not an "X-borne" disease (water, air, insect, etc.). So no, most infectious diseases that we care about do not spread contagiously. Malaria, cholera, plague, et al. Only STDs for sure.

    Individuals leaving germs in many places is not contagion if the next person to pick them up never had an encounter with the original infected!

    Look how braindead you end up by committing to this Reddit-tier I Fucking Love Science shit. One person spreads a disease through "contagion" to another person, even though the two never come within a mile of each other during their whole lives!

  3. That's your quota of one spergatarian Reddit-brain comment, BTW. I allow one of these through each time you chime in so that readers understand I'm not just making up who the other side of the debate is, what they claim, and how they don't get things that are spelled out clearly (like how ID-ing causative agents is orthogonal to modeling the spread of such causative agents through a population).

    So don't bother responding anymore to this post.

  4. A central disorder of the spergy mind is its inability to discriminate. So they can't disentangle aspects that are central, crucial, core, from those that are peripheral, secondary, incidental, etc.

    That would require sorting them into different classes, and ordering them (from most to least crucial).

    Spergs cannot do this. The whole tangle comes as a bundle, and you either reject all of it or accept all of it.

    Logical reasoners do the opposite -- mentally or in writing, they draw up a flow chart of where there are disagreements in the debate, ordered by level of specificity. This homes in on what the debate is actually about -- the fundamental split, not finer details.

    Is cholera spread by natural or supernatural means?

    Is it spread from one person to the next directly, or is it borne via some medium?

    If borne, by what kind of medium (water, air, insect, etc.)? Or if directly, through what kind of contact (skin to skin, fecal to oral, breathing, etc.)?

    And so on and so forth.

    The contagionists and miasmists both agreed that the spread was natural, not supernatural. No relevant details there. And they did not agree that it was spread through a medium, so there are no relevant details further down the chart (i.e., the particular medium that miasmists believed was the culprit).

    Rather, they were stuck at the level of "direct vs. mediated transmission". Only details pertaining to that question are relevant in judging which of the two sides won the debate.

    Verdict: miasmists won.

    Reddit-brainers like to think they're the logical, rational type, but they're incapable of the most basic tasks of logical reasoning. That's why they can't figure out jackshit.

    Instead, since everything comes as a bundle when you can't discriminate, you either wholly swallow one side of a debate or another (or another, however many sides there are).

    This is the I Fucking Love Science mindset. "Just inject it straight into my veins". Etc etc etc.

    Don't question, study, discriminate, or structure anything. Just pretend that everything comes in non-decomposable wholes, and you're simply making consumer choices about which whole to swallow whole.

    It's similar to the tribalistic behavior of non-spergy people, where it's black-and-white, Team A vs. Team B, just tell me which tribe a signifier belongs to and I'll behave accordingly.

    It's just that socially inept spergs need a non-social frame to carry out the same black-and-white thoughtless herd behavior. It's not "the view held by my tribe," but "the view consensused upon by The Scientists (TM)"!

  5. Reddit brain works by a kind of guilt by association, then. If one piece is wrong, the every piece is wrong -- just look at what other pieces this one piece is attached to, in a non-decomposable whole.

    A normal, logical reasoning brain says, "Hold up, this piece may be wrong, but that other piece is right". And if the piece that's right is on the crucial matter in a debate, then who cares about the irrelevant piece that is wrong?

    Otherwise known as "don't throw the baby out with the bathwater," although in the miasma vs. contagion case, the miasmists got it almost entirely correct -- a foul-smelling medium conducted cholera from one person to another who had no encounters.

    Same goes for the non sequitur about plague masks. Even if those were a necessary consequence of the theory (they were not), they're only one consequence. What about the other consequences, like modern sanitation, including not only ventilation for indoor spaces but also the sewage system?

    Only a spergy numbnuts would wave away the public health importance of modern sanitation, just because the counterparts of those responsible for it would have worn plague masks in a separate pandemic during another century.

    Did contagionists solve the plague pandemics anyway? Of course not -- they would've argued for skin-to-skin contact between an infected and healthy person, when in reality it was transmitted by fleas. Isolate people from people all you want -- it won't stop the fleas from getting to them.

  6. Spergs must also conclude that Galileo and Copernicus were wrong, and their heliocentric models discredited, because they thought Earth's orbit around the sun was circular rather than what it ackshually is, elliptical (discovered by Kepler).

    But Galileo and Copernicus were not debating their rivals over the shape of Earth's orbit around the sun -- their rivals denied that Earth orbited the sun at all! They said it was the sun going around Earth -- a bit more fundamental of a disagreement.

    The actual debate during their era was "sun around Earth" vs. "Earth around the sun". The Galileo and Copernicus camp were vindicated, and the geocentric camp discredited.

    The precise shape of Earth's orbit around the sun is a debate within the heliocentric side of the geo vs. heliocentric debate. You can't argue over that without first stipulating that Earth orbits the sun rather than vice versa.

    Equally, you can't debate which medium was the conveyor of cholera from one person to another at a distance, i.e. without encounters between them, unless you have already agreed that it is conveyed by a medium rather than person-to-person encounters.

    In the actual debate of their day, Snow was on the side of the miasmists because his model was of a contaminated medium, not encounters between a sick & healthy individual. He was not a contagionist, therefore he was a miasmist (only two mutually exclusive answers to that fundamental disagreement about the direct-ness of transmission).

    He only differed with the other anti-contagionists about which medium was responsible (water, not air).

  7. Spergs' non-social brains prevent them from empathizing (seeing or feeling from inside another person's mind), so they do not understand that scientific or other intellectual debates are between two historically contingent sides, in a certain time, place, and over a certain matter, with a crucial point of disagreement, while agreeing to other things, and with other details being incidental or orthogonal.

    Spergs try to evaluate a theory in isolation, from the here and now.

    "Copernicus thought the Earth's orbit around the sun was circular? Wow, that's a big yikes from me, fam, didn't he trust the experts and Fucking Love Science enough to know it was ackshually elliptical?"

    They can't see his perspective, i.e. against the geocentric camp of his day. In that actual debate, he was clearly vindicated and his rivals were discredited. Further refinement of details within his winning side of that original debate, does not alter the fact that the heliocentrists won and the geocentrists lost.

    Ditto for the debate between mediated vs. encounter-based models of the spread of cholera in 19th-C. Europe. The mediated camp was decisively proven correct, and the encounter-based side wrong, regardless of any future further refinements of which medium it was, did it smell foul or not, etc.


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