Insect-borne pathogens enrich picture of dynamics of diseases spread by shared medium, not encounters between sick and healthy

In this next installment of the revival of anticontagion theory, we'll zoom out to see how broad the class of diseases is that are described by the model. We want as general of a picture as we can manage, so that aspects of one sub-group can clue us in to what's going on in another group that's less well understood.

We've already covered a classic non-contagious disease like cholera, which is transmitted via a contaminated shared medium (i.e. water), into which the sick shed pathogens, and from which the healthy consume them, not through a sick and a healthy individual having an encounter. And we've shown that coronaviruses infecting humans and bats -- including the one causing SARS-2 -- are another textbook case, where they are spread through the medium of indoor air, not encounters between sick and healthy.

Now we return to the other major diseases that motivated the 19th-century debate over how diseases were spread -- plague and yellow fever. These are borne by insects (fleas and mosquitoes), which bite a sick person and thereby become carriers of the pathogens in the sick person's blood, then travel to a healthy person, bite them, and transfer these pathogens, making this person sick. We can add malaria and others to the list.

But first, there is one insect-borne disease that was classified as contagious -- i.e., spread through encounters -- even by the anticontagionists way back in the 19th C., which means we ought to consider treating it as such today as well. That is typhus (not to be confused with typhoid fever), which is spread by the human body louse. It was known to spread from one person to the next who were in close contact with each other in crowded settings like jails, hence the nickname "gaol fever".

What distinguishes typhus from all the others is that its insect carrier is not very mobile between human hosts -- unlike fleas that jump long distances, and which are riding on the backs of rats from one place to another, and unlike mosquitoes and flies that can fly long distances. The body louse only walks or crawls around a single host (their body and their clothing), so that the next host must be very close in order to crawl from one to the next.

This requires an encounter between a sick and a healthy person, so it behaves like other contagious diseases. For example, it does spread more as a function of higher population density, like in jails.

So technically, the diseases described by the shared-medium model are "mobile" insect-borne diseases, but I will drop that qualifier as too cumbersome, now that it's understood.

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Recall what the shared-medium model is tracking -- not only susceptible, infected, and recovered individuals, but also the concentration of the pathogen within the medium. I'll put up the formal mathematical model, and analyze it, later. First we're just getting all the conceptual stuff covered, so that the model will be motivated and make sense the first time around. Presenting the equations etc. first, and then explaining the details of it all, is putting the cart before the horse.

What, then, is the "medium" for an insect-borne disease? Why, the entire local population of the relevant insect. It may sound strange to describe it as a medium, since unlike water and air, people do not rely on mosquitoes, flies, and fleas to go about their daily business. However, those insects do rely on us for their survival -- so we very much come into inevitable contact with those species, even if it's them seeking out us rather than the other way around.

And by adding up a bunch of individual insects into an entire local population, they are like drops of water that add up to the entire local public water supply, or molecules of air that add up to the entire local volume of indoor air. The number of insects carrying the pathogen, as a share of their entire local population, is the same as the concentration of cholera particles in the water supply, or coronavirus particles in the indoor air of some locale.

A sick person "sheds" their pathogens into the medium by getting bitten by the insect, like someone with cholera excreting into the water supply, or someone with a coronavirus breathing into the air of an indoor building. Then a susceptible person comes into contact with this medium by being bitten by an insect. If it is a carrier, it's as though the person were drinking contaminated water or breathing contaminated air. If it's not a carrier, it's as though they were drinking a virus-free cup of water or breathing from a virus-free pocket of air.

Not every insect is a carrier, just as not every drop of water in the system contains cholera, and not every pocket of indoor air contains coronavirus. But as the concentration of the pathogen in the medium increases, it becomes more likely that a susceptible person will become infected by "consuming" or coming into contact with the medium.

There are differences among these shared-medium diseases, such as those whose medium is mobile -- running water in a public supply, jumping and flying insects -- vs. fairly fixed in place -- stagnant indoor air, slow crawling insects. But this is only a difference of degree, not kind, so we don't need multiple models to cover them. There will be a parameter for how frequently a sick person, or a susceptible person, comes into contact with the medium -- which will be higher for the mobile-medium diseases, and lower for the fixed-medium diseases.

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What lessons can we learn from insect-borne diseases, when looking at the prospect of dealing with SARS-2 or other respiratory diseases? Crucially, a vaccine is unlikely to solve the problem, and solutions will have to affect other parts of the environment to purify the medium -- or eradicate the medium altogether, if it's not beneficial for us anyway (like fleas and mosquitoes, and unlike air and water).

Even the non-mobile insect-borne disease, typhus, lacks a vaccine. And so do the other big ones spread by mobile insects, like malaria and plague.

The sole exception is yellow fever, but that vaccine is neither necessary nor sufficient to prevent outbreaks. The US and places under its control -- like the Panama Canal and Cuba -- eradicated the disease during the early 1900s through changing the environmental conditions. Namely, improved sanitation, spraying residences with pesticide, preventing stagnant water from forming (where the mosquitoes lay their eggs), and disrupting stagnant water by spraying it with oil. Control or eradication of the insect species remained the primary method of combating the disease during the Midcentury, when DDT was widely used.

A vaccine was developed by the 1940s, but was secondary at best even then, and did not play any role during the eradication of the early 20th C. It was beaten back in tropical regions as well, primarily through changing the parts of the ecosystem affecting the mosquitoes, not through mass vaccination of the human population.

Yellow fever has in fact reemerged as of the 1980s, despite availability of the vaccine, which does well in clinical studies but whose effects are evidently overwhelmed in the changing real-world ecologies of the past several decades. Since the most parsimonious explanation of the rise and fall of the disease up through the early 20th C. does not include the vaccine in the picture, we don't need to invoke it during the recent resurgence either.

Over the past 30 or so years, urbanization has skyrocketed in tropical regions, and since humans are the food source for mosquitoes, this has led to a surge in the mosquito population in those areas. With more mosquitoes swarming around, people come into contact with the medium far more often than before. Overcrowding strains the public water supply, so more people store their own water in large tubs near their house, which makes them stagnant and perfect breeding grounds for mosquitoes. Overcrowding strains sanitation services as well. These regions are a lot filthier than they used to be.

And perhaps just as importantly, pesticide use has fallen off a cliff, especially DDT. Pesticides are like a vaccine in that their widespread use will trigger a co-evolutionary arms race, where the target adapts by becoming resistant to the obstacle. Pesticides and vaccines also have side-effects on people, which must be weighed against their benefits.

Why shared-medium diseases are so hard to control via vaccines is a separate matter, which I'll speculate on sometime later. The point for now is simply that they are, and therefore we should not expect vaccines to do much work in controlling respiratory diseases, which spread through shared indoor air volumes, whether SARS-2 or anything else.

Improving sanitation and disrupting other parts of the transmission cycle -- before a susceptible person comes into contact with the already contaminated medium -- is the only reliable way to solve these problems. Draining stagnant water areas so mosquitoes can't breed, poisoning the rat population so plague-carrying fleas have no vehicles to get close to people, separating outgoing and ingoing water supplies to prevent cholera from passing from sewage to drinking water, and ventilating indoor spaces as much as possible to prevent respiratory pathogens from filling up the air.

SARS-1 and MERS coronaviruses spread via contaminated medium (indoor air), not encounters; beating respiratory "diseases of civilization" requires superior ventilation

Brief navigating note: I've added a new category tag for all posts in this ongoing series about diseases that are supposedly transmitted via encounters, but which are in fact transmitted via a contaminated shared medium. It's "Neo-Anticontagionism" -- "contagion" referring to contact and touching, i.e. close encounters, as the way diseases are spread. It appears at the end of every post in the series, as well as in the sidebar on the right called "Category Index". I don't know how long the series will be, but it's important and distinctive enough to put it all in one convenient place.

This post will look at the two most famous coronaviruses aside from SARS-CoV-2, which also cause acute and severe respiratory symptoms in human beings, namely SARS-CoV-1 (causing the Sudden Acute Respiratory Syndrome outbreak of the 2000s), and MERS-CoV (causing the Middle East Respiratory Syndrome outbreak of the 2010s).

I'm sure the broad lessons about transmission from these three well-studied cases will generalize to other coronaviruses that infect humans, it's just that these three have received a lot more attention and funding to study compared to the coronaviruses that cause less severe symptoms.

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If SARS-CoV-1 were spread through encounters, then it should have crossed the species barrier outdoors, since bats (the virus' reservoir) have encounters with other species outdoors. In fact, of all their inter-species interactions, most take place outdoors because when they are indoors roosting, they are far within the depths of their protective caves, where only their fellow bats and some cave-dwelling animals live.

Also, the list of species to whom bats transmitted the virus should resemble those whose habitats are close to, or overlap with, the habitats of bats. Those would be the species with 1 degree of removal from the reservoir -- of course it could then be spread to other species in contact with the 1-degree species but not the bats themselves. But a 1-degree ring of species around bat-colonized caves should be identifiable.

In reality, the other species that bats gave SARS-CoV-1 to were localized within a single market in Guangdong, China (see here). These multiple inter-species crossovers could not have easily happened in the wild, given their vast and not-so-overlapping range of habitats. But when they are all concentrated into a single place, by people who trade in wildlife of various habitats, then these crossovers with multiple species are easy.

The market was not for dead animals being sold for food or their pelts, but a live-animal market for wildlife. It was enclosed and informal, not an open-air market, nor one with advanced HVAC and filtration systems to achieve aircraft-levels of ventilation. So an infected individual was alive, exhaling into the fairly stagnant air volume, from which all the other individuals -- of whatever species -- were inhaling.

As we saw with SARS-CoV-2, the alternative model of "high population density and more frequent encounters" can be ruled out by the specifics here. Namely, because the animals were being sold, they were all caged and grouped by species -- here's a section with a bunch of palm civets, there's a section with raccoon dogs, and so on. Some sellers would only have one of these species for sale, preventing contact with other species.

The density / contact model could only explain the spread among individuals grouped tightly together -- this particular grouping of palm civets in this particular seller's stall. Or if that seller had palm civets and raccoon dogs grouped next to each other, then among that combined population. The animals are not roaming around the market, so they cannot spread it through encounters with any other animals in a different stall.

The only mobile species that could transfer the virus from one place to another within the market is humans -- some guy spends a lot of time in close contact with animals in one place, wanders somewhere else, and spends a lot of time in contact with other animals. However, that would implicate customers or shoppers who spent a long time browsing around the market -- but in fact, it was the workers of the market who made up most of the SARS cases, and they spend most of their time in their own stall tending to their own population of animals. They are the least mobile and free-ranging of the humans in that market.

These facts can be explained, though, by the model of a contaminated shared medium, namely a poorly ventilated indoor air volume. The virus particles get an initial impulse when pushed out of the lungs during exhalation, so they can coast or glide for awhile, in addition to their movement by diffusion. They can -- and do -- travel through space, without needing an infected individual to move around as their vehicle. When an animal, of whatever species, inhales these particles that have traveled far from their source, they get infected in turn -- without an encounter.

That explains why multiple individuals of one species get it, why the same species gets it no matter whose stall they're in, and why multiple species get it -- all of them are connected by the shared volume of enclosed, stagnant air. It also explains why workers get it more than shoppers -- they spend far more time immersed in the market's enclosed air volume.

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MERS-CoV got less attention because the SARS-1 outbreak happened in the wake of 9/11 and the anthrax outbreak, which primed everyone to be more vigilant about a novel respiratory disease that could be spread by terrorists or hostile foreigners. That post-9/11 mood had faded by 2005 or so, and by the time of the MERS outbreak in 2012, it had all but dissipated -- even though this new disease was coming from Saudi Arabia and had the phrase "Middle East" in its name. And ISIS was chopping off heads, not using bioweapons, so there was nothing big in the background to make people pay special attention to MERS.

But it did get scholarly attention because it was another new coronavirus infecting humans, so maybe it could shed light on SARS and help us prevent any further coronavirus epidemics. Nope! They drew the wrong lessons, based on the reigning false model of diseases spread through encounters, and here we are now with SARS 2.0. Again, the current coronavirus is not deadly enough to need to stop society in order to solve it, but the people investigating SARS and MERS should have been able to prevent it, or at least deal with it based on reality after it was already unfolding, rather than continue to treat it as a person-to-person encounter disease, instead of the contaminated shared medium disease that it so obviously is.

MERS' reservoir is a microbat species that prefers shelter while roosting, as usual. (It does have an unusually cool name, though: the Egyptian tomb bat.) The main species it has crossed over to is dromedary camels, and to a lesser extent humans.

With their usual contagion-theory blinders on, researchers focused on the fact that a man who had died of MERS had been in close contact with a camel that was also infected, indeed he had been applying medicine to its nose which showed strange secretions. The inference is that the virus was present in the nasal secretions, the man touched these secretions, and then his own nose or face, which sent it into his lungs, spreading the disease through a close-contact encounter.

But how the hell did the camel get it from the bat? Did a healthy camel sniff a sick bat's secretion-oozing nose? Or maybe the bat felt mischievous and targeted the camel, smearing its nose on the poor camel's nose, while taunting him with, "Now you got my gerrrrms, now you got my gerrrrms!"

C'mon, people.

One team came close to the truth, when they found MERS-CoV in an air sample collected from the barn of a camel-owner who had come down with MERS, and whose camels were sick with MERS (see here). This proved it could be airborne, that it could stably aerosolize, and that it was at the scene of the crime at the right time.

But as usual, airborne or aerosolized respiratory diseases were treated as spread through close contact, i.e. the proverbial "cough or sneeze in the face". "Proverbial," and yet an act which has never actually happened between two individuals of any species, at any time in our planet's existence. However, it is required by the ideology of ballistic / encounter-based models, so it simply must happen so frequently as to be proverbial.

And again, how could the camel get it from the bat? The human owner was close to the camel -- close enough to be applying medicine to its nose. OK, maybe it spreads directly in an airborne way over a distance of several feet. But bats roost way up on the ceiling of the barn, or high up on one of the walls. The bat was not roosting within several feet of the camel's head. Therefore, close contact (airborne or otherwise) is ruled out.

Only the shared medium model explains the multi-species crossovers. The bat finds a structure where it can roost, and this camel barn is poorly ventilated like all houses for livestock. While roosting, it exhales into the stagnant enclosed volume of air in the barn. While not roaming around outside, the camels stay in the barn breathing that air. The human owner of the camels also spends time in the barn doing various chores, breathing that air -- whether or not the bat is there at that time (it could be out foraging), and whether or not the camel is there at that time (it could be out grazing). Other humans could enter the barn, for that matter (such as a guest who is just chatting with the owner, while both are inside the barn).

Since the aerosolized virus particles get both an initial boost during exhalation, as well as diffusion, they can travel from way up where the bat is roosting, to where the camel is resting, or where the human is doing his chores. The stagnant indoor air connects them all.

A later review article (see here) provides further confirmation of the shared medium model, although it is not aware of that. It looks at various factors to explain why MERS is emerging in the Arabian peninsula during the 2010s. One major factor they point to is the sedentarization of nomadic pastoralists, owing to the immense wealth that the Gulf states (such as Qatar) began to enjoy after nationalizing their oil and gas supplies (mostly completed by the 1970s), and as they began to spend some of that wealth to encourage the nomads within their populations to settle down, so the state could better administer them.

Camels that are part of a nomadic herd do not spend any time at all inside of an enclosed volume of air. There are no permanent structures for dwelling or gathering, and even the tents that are put up temporarily are for people and their things, while the camels rest outside of them. Only when nomads begin to sedentarize, do they build permanent dwellings for their livestock, like barns.

Bats are not drawn to roosting near nomadic herds, since there is nothing for them to hang from on a regular basis. Perhaps their tents -- but those are only good for a short while, and then they're gone. Bats want a reliable den to provide security, not having to tag along with a nomadic group, which would be far and few between. Only the sedentarization of the nomads would bring a structure that would tempt the bats to roost inside of -- the barn (and perhaps the human owner's home, although that space is more vigilantly policed by its dwellers).

Notice again the inability of the contact / encounter model to explain these facts that attend sedentarization. Camels and their owners are in close contact all the time when they are nomadic -- being ridden, being tended to, being shown affection, being milked, and so on and so forth. Whatever pathogens infect camels, have ample opportunity to cross the species barrier to humans. And yet, no MERS-like crossover events among nomadic camel-owners -- only when they settle down and build barns, which does, however, introduce a shared medium that could become contaminated (indoor air).

Contact theory could explain why bats don't spread disease to camels in nomadic settings, because they have no close encounters outside of barns. But the shared medium explains this as well, in addition to all the other crucial facts.

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Let's end with a return to the grand historical view, in which I think most respiratory "diseases of civilization" adapted themselves to the shared mediums that only arose with sedentarization, such as the indoor air of buildings (akin to waterborne diseases arising with public water systems). The case of MERS shows this in-tandem development unfolding in real time, as nomads settled down and instantly got stricken with an infectious respiratory disease.

Pathogens that travel through a respiratory route have almost no chance of spreading in epidemic fashion among nomads, because the currents of a fresh-air environment will scatter them quickly, rather than allow them to build up within a highly-visited space.

Adapting ourselves, and our livestock, to these sedentary environments requires sanitizing them. Not by spraying antibacterial disinfectant on all surfaces -- that's not how they spread. But by treating the medium with a pathogen neutralizer (that has no bad side effects), or creating some kind of current that will carry the pathogens quickly away, or separating outgoing from ingoing channels of that medium.

In the case of contaminated indoor air, the solution is improving ventilation and filtration, to such an extent that earlier times will look as backward as we presently view the public water systems of the pre-20th-century West.

Coronaviruses spread via enclosed air, from bat caves to indoor buildings, not via encounters: a window into respiratory diseases of civilization

To recap the project I've stumbled onto, most diseases thought to be transmitted through personal encounters are in fact spread through a contaminated shared medium, into which a sick individual emits pathogens, and from which a healthy person takes them in -- without needing to be in the same place at the same time, perhaps never coming close to encountering each other during their entire lives. See here for the overview based on the case of 19th-C. cholera in Europe, and here for the contemporary example of SARS-CoV-2 (causing COVID-19).

This post will briefly look at the non-human origin of coronaviruses that now infect humans, and how their transmission dynamics can shed light on how they circulate within a human population.

Recall the most important fact about the transmission of SARS-CoV-2 -- it never occurs outdoors, but only indoors, especially where ventilation is poor. This means the particles are suspended in a stagnant air volume, much like a pond of stagnant water. A sick individual exhales particles into the enclosed air volume, and at some other time, perhaps after the original sick person has left the building, someone else enters the building, immerses themselves in the now-contaminated air volume, and breathes the particles in, becoming sick in turn.

All of these coronaviruses that infect humans ultimately come from pathogens infecting bats. (A separate family of coronaviruses originated in rodents, and infect pigs and other livestock, but via a fecal-to-oral route).

What do bats do? They roost -- hang upside-down while not active, and seek shelter when they are so vulnerable. The large bats that could take on predators may roost in forests, but the microbats that are too small to defend themselves mano-a-mano, roost in more defensible environments like caves. Human-infecting coronaviruses come specifically from these microbat species.

What is a cave? A great big "indoor" enclosure of air, with minimal ventilation inside, and whose opening to the outdoors is small relative to the size of the interior. Ventilation is basically zero where the bats roost -- not right inside the entrance, which would make them easy pickings for predators, but deeper back into the recesses of the cave.

Crucially, these caves are communally shared -- it's not like each bat or its family has its own detached bat-cave like Batman does. There are a whole bunch of them in there, coming and going without any bouncers to regulate the entrance. So the cave air is not only stagnant, but acts as a public medium that connects all of the individual bats that exhale into it and inhale from it, much as a stagnant pond of water connects all of the fish that swim within it -- or all of the ducks that feed from it (but that's for a later post on the non-encounter-based spread of influenza!).

So, one infected bat exhales while roosting in the cave, and the virus particles become aerosolized -- they are part of that air volume, just as inseparable from it as the oxygen. Healthy bats inhale air from this now-contaminated medium, not necessarily right next to the original sick bat. The virus particles travel by diffusion, which is slow, but they also start off with an initial impulse coming from the pressure that the lungs exert to expel the air from within the bat into the surrounding air (even more oomph in that initial burst if the sick individual has a cough or sneeze, as in humans).

The end result is that virus particles spread to regions of the cave far away from the source bat. It doesn't matter if it takes awhile for this spread to happen -- the sick bat is holed up in there roosting for hours on end, day in and day out, and the same is true for the healthy bats. A healthy bat may have a preferred roosting spot that is "far" from the roosting spot of the sick bat -- outside of the distance that a typical breath, cough, or sneeze immediately reaches -- but given some time, those particles can travel to reach him, too. Proximity is not needed.

However, couldn't you explain this indoor transmission by appealing to population density, which is required by the direct contact / encounter model? I.e., if transmission happened through encounters, such encounters are more likely when individuals are packed more tightly into the same space. So a bunch of bats roosting in clusters could be spreading it to each other through close encounters, not through a medium like the stagnant air.

But there are two facts that rule against this alternative explanation. First, it only says that transmission would be greater inside the cave than outside of it -- not that outdoor transmission would be near zero. And bats do in fact encounter other bats, and other species, outside of caves, for enough time to breathe near them and pass along pathogens. And yet spillover from bats to other species only takes place where the two species share an indoor air volume (typically poorly ventilated), such as an indoor market or restaurant. Not out in the wild.

And second, these coronaviruses should also be endemic to the macrobat species that roost in trees rather than caves. They also hang around for hours on end, and in clusters where they are in close proximity to one another. The difference is that these environments have superior ventilation, being outdoors. A really dense forest with leaves enshrouding the branches, or that form a canopy and "walls", could be somewhat of an enclosure, blocking the totally free flow of air. But even that is much more open to air currents than caves.

And forget about it if it's anything other than a tropical rainforest. Bats that roost in trees like you see in a typical park are not immersed in an enclosed volume of stagnant air at all. No structure is enclosing the trees, and the branches and leaves of the tree itself leave lots of open space in multiple directions to the "outside" world.

So much else is shared between the microbat and macrobat species' physiologies, that it should be trivial for coronaviruses to plague the tree-roosting macrobats -- and yet it's only the poor cave-roosting microbats who are beset by coronaviruses. Only the model of a shared medium can account for that, not the encounter / density model.

If some disease were spread among macrobats in trees, it would be the tree that was the public medium connecting all of the individuals. Perhaps if a pathogen they picked up on their feet penetrated the tree bark and spread from one branch to another, where it infected another bat who was roosting far from the original sick bat. But not a pathogen that travels through the respiratory route -- there's no enclosed medium of air in a tree.

That wraps up the proof that coronaviruses among bats are transmitted not through encounters, close contact, and higher density, but through a contaminated shared medium.

We can draw a further lesson, though, by noting that a pathogen is far more likely to cross a species barrier if the new ecology is similar to the old ecology. Fewer selective sweeps of random mutations would be needed to adapt the pathogen to its new host species.

So, is there any similarity between the environments that cave-roosting bats inhabit, and human beings? Well, if those humans have sedentarized and spend enough of their time within enclosed structures, especially ones that are shared with multiple other people. Not hunter-gatherers, and probably not nomadic pastoralists. But agrarian and industrial societies? Absolutely. I think that's what the respiratory class of the "diseases of civilization" are -- pathogens adapted to stagnant indoor air of shared buildings, scarcely different from those infecting untreated public water supplies that arose with sedentary agrarian societies.

And sadly for the animal species we have domesticated, these conditions apply to their structures as well. Unless they belong to purely nomadic pastoralists, they spend a fair amount of time within an enclosed building of some kind -- a barn, a stable, a doghouse, something. Both to corral them into an easily manageable place, rather than chase after them individually, but also to protect them from predators, and provide shelter from the elements.

And in an even sicker twist of fate, their human owners spend a decent amount of time in those animal buildings as well -- they aren't like a detached guest house, where the livestock do their own thing and take care of themselves. Human beings enter those animal buildings to tend to their needs, spending a fair amount of time immersed in the same stagnant volume of air as their animals. Crucially, humans enter the animal building even when the animals are not there -- to clean the place up, to restock the animals' feed, and other barn chores.

That sharing of stagnant air is the route through which a respiratory pathogen crosses the species barrier between humans and their domesticated livestock -- not direct contact or close encounters, since the sick animal could be outside the barn at the time their human owner is inside it doing chores. But the stagnant volume of air containing aerosolized virus particles is still there, even when the animals are out and about, due to limited ventilation.

In the next post in this series, we'll look specifically at two more coronaviruses that have crossed from bats to humans, and perhaps some intermediate species along the way. Namely SARS-1 and MERS. Both cases confirm the model of transmission through a contaminated shared medium rather than encounters between the sick and the healthy.

Coronaviruses spread through contaminated medium (indoor air), not personal encounters; solution is sanitation of spaces, not targeting individuals

Having looked at the history of cholera in the previous post, we'll draw some lessons for the current SARS 2.0 pandemic (COVID-19), and in a follow-up post, the outbreaks of SARS 1.0 and MERS in the 2000s and 2010s. That is, the other coronaviruses that were harmful to human beings. The pattern probably extends to other coronaviruses, and other respiratory infectious diseases, but I'll stick to these three cases since there's a lot of interest in them, hence a lot known about them, and they're part of the same family.

First, though, the current pandemic is not harmful enough to warrant a "drop everything" effort to eradicate the virus. It is far less deadly than SARS 1.0 and MERS, or influenza for anyone under 65 or 75. This is not a contribution to the Zero COVID insanity, or anything like that. This is strictly an investigation into the transmission dynamics of this family of viruses, and of respiratory infectious diseases more broadly.

The mathematical models they require are very different, and more complex, from the standard epidemic models (S-I-R), as the pathogen is not spread through person-to-person encounters, but through a medium -- into which a sick person sheds pathogens, and from which a healthy person contracts them, all without having to be within a mile of each other for their entire lives. Instead of only tracking individuals who are susceptible, infected, and recovered, we now need to also keep track of the concentration of the pathogen in the medium, and describe how the susceptibles and infecteds interact with this medium, since they do not interact with each other (for disease transmission). From a 3-variable system of differential equations, we must expand into a 4-variable system.

But the math models will wait for another post. The purpose of this post is to properly frame and understand how these coronaviruses are transmitted, what this implies about any attempts to control or eradicate them, and how broadly the results generalize to other respiratory diseases. For while COVID-19 is nothing more than a bad cold, it would still be nice to not have yet another source of bad colds, if the solution is cheap and easy (unlike the expensive, difficult, and failed attempts so far -- masks, social distancing, lockdowns, vaccines, etc.). And if the solution is good, it will impact all sorts of pathogens transmitted in the same way, not just the relatively benign one that causes COVID-19.

Let's start with SARS-CoV-2, the virus that causes COVID-19. The most stunning fact about its transmission is that it never takes place outdoors. This alone eliminates the person-to-person encounter model -- people encounter other people outdoors all the time. The virus travels through the respiratory route, and people breathe all the time out in the open, not just in the privacy of behind closed doors. And yet, no outdoor transmission. Conclusion: it's not passed along through encounters.

It only gets transmitted indoors, especially where ventilation is poor. In that case, the indoor air is acting like a stagnant pond of water -- a medium that is just as physically real as any liquid or solid. Spergs seem to have a problem understanding that the gaseous phase of matter is still matter, but it is. And the more enveloped it is, with little escaping or coming in, the more it is just like a stagnant pond.

All of the super-spreader events have taken place indoors, with poor ventilation. Spring Break on a Miami beach? No. But a church group meeting for an hour or so in the same room? Yes.

One exception to this rule is the inside of an aircraft. These should be ideal super-spreader environments, since people are packed in there for hours on end, drawing passengers from all sorts of different places where the virus could be spreading. And there is a known roster of who was there -- zero difficulty for "contact-tracing" methods that would lead investigators back to a particular flight that all the sick people had taken.

Why don't aircraft interiors serve as super-spreader spaces? Because their air is refreshed -- old air sent out, new air drawn in -- at a far higher rate than just about any other space that ordinary people find themselves in (offices, homes, restaurants, retail, etc.). Think about it: have you ever entered a plane and felt like it was even remotely musty, stuffy, stagnant? Hot during summer, maybe, but not oppressive in its air quality.

Of course, someone infected could travel by plane and spread the disease once they landed and entered some other indoor space with poorer ventilation than a plane. But not to the other passengers and crew during that flight itself.

Immediately we discover one of the most powerful ways to stop the spread of this and similarly transmitted pathogens -- amp up the refresh rate of the air indoors. Natural ventilation would do well, but if that's not feasible, then through the HVAC system. Whether or not the increase in power costs would be justified by the decrease in disease cases is an empirical matter, and could vary from one virus to the other. But it's the best place to start.

Note that this solution has nothing to do with individuals, whether sick or healthy. It's changing the environment where the contaminated medium is located. This would be akin to altering a stagnant pond of water into a moving river supplied by a fresh mountain spring. Whatever germs that had been deposited in one part of the river by a sick person would be carried away by the current. Always safer to drink running water than stagnant water.

* * *

The specifics of how a COVID-19 victim deposits virus particles into the indoor air is not too relevant. We could be wholly ignorant of microscopic phenomena, and still conclude that this thing is transmitted through stagnant indoor air, and try to solve it by improving ventilation. But as it happens, we do know how the virus contaminates the medium: a sick person enters the indoor space, expels air from their lungs in various ways (breathing, talking, coughing, etc.), and the particles are small enough to become suspended in the air (aerosols).

It's like mixing sugar into your coffee -- once you do so, it's part of the coffee. The sugar crystals are not large enough to sink to the bottom, and they're just mixed throughout the entire volume of liquid. You can't drink your way around them -- every sip has some sugar in it.

Virus particles exhaled into indoor air is not quite as thorough of a mixing process -- nothing is stirring them all around the indoor volume to get them everywhere. But their tendency is to diffuse in every which direction, so they will mix themselves evenly into the air (although diffusion is a slow process). Most likely there are clouds of particles where the sick person had exhaled, and other virus-free pockets far away where they had not been. However, there's no way to detect these virus clouds through any of your bodily senses, so there's still no way to navigate your way around them. Once they're there, someone's bound to walk through them and breathe them in -- perhaps minutes or hours later, without having any encounter with the sick person who exhaled them.

The main things that affect how many virus particles there are in the medium are the number of infected people who come into contact with it, and the duration of their contact. Does some supermarket have only 1, or maybe 10, or 50 infecteds wander through it on a given day? And do those infecteds wander around for just 5 minutes or 50 minutes exhaling particles?

The same is true for how many new cases a given space can generate -- how many susceptible people wander through it, and for how long of a visit?

* * *

Now we see why lockdowns, social distancing, masks, and even vaccines are not working to stop the spread.

Lockdowns left several crucial buildings operating, like supermarkets.

Social distancing came from the incorrect view of close personal encounters as the transmission, while also forcing people -- sick and healthy alike -- to spend more time immersed in the medium, as they have to take more winding paths to avoid others.

Masks are too crude to filter out the tiny virus particles, but they did trick people into spending more time immersed in the medium because they thought their face-armor was a magical protector. This also increased the number passing through, who otherwise would've stayed away without their supposedly magical armor.

Vaccines seem to be playing a similar role, encouraging more people to pass through a space, and to spend more time inside it, fooled into believing they're magically protected. If they neutralized the virus, that would be one thing, but they don't appear to do that, only ameliorate symptoms, which means they're about as useless as masks at stopping transmission. They may in fact be worse than masks in that regard, since masks do not ameliorate symptoms -- so if you got it, you were laid out for several days to a week, and you were not going to indoor spaces outside the home. The vaccine lessens your symptoms, leaving you more able to leave the home and spread your virus particles throughout indoor spaces.

Of course vaccine mandates are even worse, compelling even more people to become not-so-bed-ridden spreaders if they contract the virus.

Strange, isn't it? All of the mass-scale solutions have been totally ineffective at stopping the spread, clamping down on hospitalizations, deaths, and so on. And we're only just getting started in the autumn season -- get ready for winter!

These solutions all failed because they were based on the personal encounter model of transmission. They're all about minimizing risk when two people come near each other, as though COVID-19 were an STD, and The Experts were telling you to wear a condom and get the HPV vaccine. But that's not how this sucker works.

The main thing we can do is to sanitize the indoor air quality. Improve natural and artificial ventilation to fully change the air more often, so that virus particles that enter the medium do not hang around for very long. Improve filtration to remove particles. Perhaps put something into the air to kill the virus, if such a substance exists, and if there are no side-effects to breathing it in -- highly doubtful, but still a possibility, better than vaccinating every last individual.

These are the lessons from cholera, another example of an infectious agent spread through a medium rather than person-to-person. Unfortunately we cannot separate outgoing vs. ingoing air volumes, like they were able to do with sewage water vs. drinking water. That leaves the other methods of sanitation (improving flow / reducing stagnancy, filtration, treatment with virus-killers).

* * *

I doubt these improvements will be made in my lifetime, and highly doubt they'll be taken up during the current pandemic. Just as the anti-contagionist John Snow did not solve the cholera pandemics of his day simply by figuring out what medium was transmitting the disease. Too many other interests at play in public health.

For one thing, sanitation places all the costs on the elites, whether private or public. A single individual citizen cannot do anything to alter the ventilation of any indoor building outside the home. That's on the owners and operators of the buildings. He could try pressuring them, but I mean he is unable to do anything in virtue of his role as a lowly citizen, whereas owners and operators can make changes any time they feel like it.

We live in a time of wicked elites, not benign or mutualistic elites. Just like John Snow's climate, living in Dickensian / Victorian England. Not until the Progressive Era and New Deal did they finally clean up the water supplies and end cholera. Our wicked elites would rather every one of us shoulder the burden -- stay apart from each other, wear a mask, get the jab, etc. (And even then, to no effect.)

I imagine Dickensian elites had a similar "let them eat cake" attitude toward solving cholera. Just stay away from other people who show symptoms of cholera, or stay away from each other altogether. Put a cloth -- any old cloth -- over the mouth of your glass when you drink water from it that might be contaminated with cholera. If you have cholera, put your excretion through a baking sieve before it goes into the sewer. We must all do our part.

If they'd had vaccines back then, their Dickensian elites would've said the same thing as ours -- everyone get a jab so that when you come into contact with a public water supply that we refuse to clean up, you won't come down with such nasty symptoms when you inevitably contract the pathogen.

Or maybe they would've said just build your own private water system. Don't ever drink from the public one, and don't ever send your excrement into it. Then what's the point of it being there? Exactly like the "stay home" solution -- sorry, you can't avoid indoor spaces outside the home, even if you do have a fake work-from-home job. We all have to go to indoor places outside the home, and we all have to breathe, just as we all have to excrete and drink.

Sanitation of public goods and spaces is what we need, not the impossible task of isolation from those necessities.

The other major reason I don't see the correct decision being made anytime soon is that sanitation of public spaces is a unifying solution, and our current climate is one of hyper-polarization and antagonism. There's no way to identify if you're a member of Team Us or Team Them, if the elites are just cleaning up the indoor air. No masks to wear as tribal membership badges. No personal decision whether or not to get vaccinated, or whether or not to submit to vaccine passports, and so on and so forth.

Americans, and those in their sphere of influence, are a crumbling empire, going through a disintegrative phase. They are dead-set on antagonizing their so-called fellow citizens, and polarizing any situation that might offer a common solution.

Again, the current pandemic is not a huge problem in need of solving at the expense of everything else. But it would be worth terminating if it were cheap and easy. And future pandemics might not be so relatively painless as this one. Not to mention existing respiratory diseases -- might be nice to get rid of some of those, too.

But none of that will happen until the polarization reaches a maximum, and after that cataclysm, the elite ranks get thinned out, with the remainder not wanting to be so antagonistic and polarized as earlier, lest the cataclysm strike all over again. This is a description of how things work, not a consultant's pitch to a team of managers about "here's your problem, now here's your solution". They won't listen, and you're just LARP-ing by behaving otherwise.

Somebody has to set all this stuff down, though, for the record -- and in the hopes that it gets preserved long enough to be useful when the society has survived the cataclysm, and the elites become less wicked after passing through the Great Winnowing.

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.