Pan demos aeras
Disclaimer: I am still not an epidemiologist, don't believe me.
Marines, liquid science, muscular tissues. Fast forward 18 27 months. Where are we? I am still alive and would like to keep it that way. Covid is also still alive and would like me dead. I don't do Covid research for a living (income). But I do Covid research for a living (breathing and moving). I really didn't want to be an expert in this, but now I have to. How do we make Covid-related operational decisions given the data coming from the world?
"Knowing certain principles frees us from needing to know certain facts". This is the basic idea of scientific inference - we would like to have a simple, transferable understanding of empirical patterns we might encounter. If we were to perform careful controlled experiments, we could use Occam's razor to find the simplest explanation. But instead of experiments we have to face a deluge of agenda-laced messaging: a lot of messages want to exploit you, but others want to help you, and you need to tell them apart. It's time to put down the Occam razor, pick up the Occam machete, and call some bullshit.
What are the empirical patterns coming at us and begging for explanations? Covid has all but disappeared from the news cycle, several politicians have declared the pandemic over. The number of cases reported by PCR lab tests is dropping in many localities. People keep dying. People keep dealing with Long Covid, and it is long. Non-Covid viral and bacterial infections suddenly became more deadly. Masks disappeared from public spaces. Your friends who used to have strong principles regarding masks and public dining don't seem to hold to those principles anymore. The words "post Covid" are repeated like a daily positive affirmation, like a morning mantra.
What explanations of these Covid patterns float around and what mitigation strategies do they imply? In many cases, the proposed mitigations betray the model to which an entity is committed. The simplest explanation (you might call it a null model or business-as-usual) is "this is not happening" or "this happened before but the pandemic is done here". The corresponding mitigations are none. If a group of people, a company, or a government remove all Covid precautions, they believe Covid is not here. But if you have any trust in the data, or any empathy for others, this explanation doesn't fit the data.
The next explanation is the droplet theory: Covid is here, it is spread by infected people coughing out liquid droplets that stick to surfaces. New infections appear through the droplets or contaminated surfaces, just a few new cases from each previous one. If an entity recommends hand washing and puts up hand sanitizer stations everywhere, this is what they believe in. Before vaccines, we could deal with droplet spreading through social distancing. Six feet or maybe some extravagant two meters should do it, let all the droplets fall on the ground. This explanation is not terrible, and these mitigations likely saved a lot of lives. These mitigations are better than thoughts and prayers.
There is a caveat are some caveats though. There is long-distance superspeading. There are infections through walls. There are infections in which the new person enters the room after the previous one has already left. These should be very rare if the droplet theory were the whole story, but they stubbornly persist. We are stubbornly fitting a Gaussian distribution to fat tail data: rare events are exponentially more likely than you thought.
A better explanation, with a more realistic physical picture of Covid particles, and better fit to epidemiological data, is the airborne or aerosol theory. If the Covid virus were attached to particles not of hundred-micron size but much smaller, it could linger in the air for hours instead of seconds, and thus spread to any place the air flows take it. Humans routinely produce aerosols of that size, more intensely when shouting, singing, or exercising. Superspreading immediately becomes possible and even likely. The virus can linger in the air after the infected person has left, and can spread to other rooms through ventilation.
Why don't we accept the airborne theory and build it into the foundation of all the public health messaging? Why do the public health agencies push hand-washing, betraying their commitment to the droplet theory? It might be due to a subtle misreading of an old paper on pathogens that accidentally became canonical. It might be because of over-confidence in vaccines. It might be due to sunk cost fallacy and the desire to keep authority. It might be because the mitigations implied by the airborne theory are expensive and politically challenging. But the evidence for aerosol spreading accumulates and becomes more and more systematic and fine grained.
If infected people breathe out a dangerous pathogen into the air and other people breathe it in, how do we break the transmission chain? We break it at three points: exhalation, room air, and inhalation. Exhale and inhale are well mitigated by masks, and masking both the sources and the targets of infection might be superlinearly more efficient than either alone. The air in between can be easily filtered by HEPA filters that are broadly available and affordable. You can get a commercial version with a bunch of electronic features, or a standardized DIY Corsi-Rosenthal Box that works just as well. As a side bonus, air filtration would immediately cut down on non-Covid airborne pathogens, other air pollution such as vehicle exhaust and forest fire smoke, as well as many typical allergens.
The dream solution would be to build air filtration into the ventilation systems within the building's walls, as we did for running water. Any building, especially a big one, already needs to move air to regulate temperature and supply fresh outdoor oxygen to the residents. High CO2 concentration is a good proxy for badly-ventilated spaces, even the winemakers know about it. Adding a HEPA component to the ventilation system is an engineering challenge, but not an impossible one.
The messaging of the #Covidisairborne activists can get repetitive. They are, after all, trying to push the needle against the might of national and international public health organizations [they succeeded in some institutions]. They are trying to work out the exact words that would be convincing to the public bombarded with endless messages. But I only find them tiresome because they already sold the idea to me, and I am not in the target audience anymore.
When I joined... [~end of transmission~]
[...]
I began writing this text in early 2023, having already been aware of the key arguments and timeline in the airborne story. However, with time and other demands for my attention the text never got finished. I still wore masks, used air purifiers, and reminded people of Covid existence. I tried to run risk calculations about attending different in-person events. However, I didn't care enough anymore to finish the text.
This all changes, of course, with your first real big-boy Covid infection, the fever without sweat, the inability to follow a simple entertainment YouTube video, the total discombobulation with reality. And the reality and the price tag of treating a moderate case within the American health insurance world. My risk calculation took me to a fun, but dark and poorly ventilated room, the kind that Covid likes the most.
I got over the acute Covid. Time will tell whether I get the long one. So here is a grafted message, before the grifters make you forget all about the deadly virus. Covid sucks but it doesn't stink. Because I can hardly smell anymore.
When I joined my current position, our research group moved into a new space that was previously unoccupied. I showed up to the informal orientation in a trusty KN-95 and asked about the Covid policies. By Fall 2022, university Covid policies seemed mostly gone. Yet by miracle, inspectors from occupational health and safety visited our office and declared Covid to be the prime occupational hazard. Two standalone air purifiers were installed within two days. I looked up the exact model and made sure that two of those can ensure 6 air changes for our office area. In absence of enthusiasm from others, I put one of the purifiers next to my desk. In the past year, nobody caught Covid in that space.
If you are reading this, chances are you follow the news from some authoritarian country - and I don't mean any specific one here. A proper authoritarian government would never let a good crisis go to waste. Covid crisis is a great excuse to lock people up in homes, install permanent emergency measures, and say that was the only possible solution. Words like #ZeroCovid often abuse notation: they refer to a problem, an objective, and a method all at the same time. The objective is a noble one: after all, we would not worry about Covid anymore if it were truly gone.
Even outside of explicit authoritarianism, instead of zero Covid we reached mostly unknown Covid. Covid case dashboards went dark. Centralized and logged lab PCR tests are few and far in between. I just threw away a stack of used rapid antigen tests that tracked my recovery, but I never showed them to any authority. Genome sequencing for variant tracking is a few percent of what it was at the peak.
So the pandemic is over - not by numbers, but by decree. Pandemic is over, therefore we will take away tests, treatments, vaccines. We will stop mask mandates - no, scratch that, we will ban mask mandates. We will stop infection surveillance, because you only need to know the lagging indicators such as hospitalizations and deaths, after they happened. We will force people back into work. We will force people back into offices and take away the sick leave. If you get a positive Covid test today, it means the same exact thing as it did 3.5 years ago: you are a public health hazard to others and need to isolate and get treatment appropriate to your disease severity. Only now you cannot.
[~transmission resumes~]
Lately I've been censoring my speech to never say out loud the words "post Covid", because it is not gone. Covid is not planning to go away, you can't budget your life to catch Covid N times in the next T years. Your life will get much worse with growing N, but T is not finite. Covid is in the air, but unlike the whiff of historical events to come, Covid can actually be easily removed from the air.