An Uneasy Relationship With the Air

Review of Airborne, by Carl Zimmer. 

The pandemic was tough on everyone. But it had especially damaging effects on the political system, and on its relationship to the scientific community. Now the wingnuts are in charge, blowing up the health and research system, which obviously is not going to end well, whatever its defects and whatever their motivations.

While the scientific community had some astounding wins in this pandemic, in virus testing and vaccine production, there were also appalling misses. The US's first attempt at creating a test failed, at the most critical time. We were asleep at the wheel of public health, again at the earliest time, in controlling travel and quarantining travelers. But worst of all was the groupthink that resisted, tooth and nail, the aerosol nature of viral transmission of Covid. That is, at the core, what Zimmer's book is about, and it is a harrowing story.

He spends most of the book strolling through the long history of "aerobiology", which is to say, the study of microbes in the air. There are the fungal spores, the plant pests, the pollen, the vast amount of oceanic debris. But of most interest to us are the diseases, like tuberculosis, and anthrax. The field took a detour into biowarfare in the mid-20th century, from which it never really recovered, since so much of that science was secret, and in its shadow, the sporadic earlier public studies that looked carefully into disease transmission by aerosols were, sadly, forgotten. 

So it became a commonplace at the CDC and other public health entities, among all the so-called infectious disease specialists, that respiratory viruses like influenza, colds, and coronaviruses spread not by aerosols, but by contact, surfaces, and large droplets. This made infection control easy, (at least in principle), in that keeping a few feet away from sick people would be sufficient for safety, perhaps plus surgical masks in extreme situations. There was a curious disinterest in the older studies that had refuted this concept, and little interest in doing new ones, because "everyone knows" what the virus behavior is.

It is hard to explain all this in purely scientific terms. I think everyone knew at some level that the true nature of respiratory virus transmission was not well-understood, because we clearly had not managed to control it, either in residential or in hospital settings. It is hard to grapple with invisible things, and easy to settle into conventional, even mythical, trains of thought. First there were miasmas, then there were Koch's postulates and contact by fluids. It was hard to come full circle and realize that, yes, miasmas were sort of a thing after all, in the form of aerosols of infectious particles. It was also all too easy to say that little evidence supported aerosol spread, since the work that had been done had been forgotten, and the area was unfashionable for new work, given the conventional wisdom.

Even more significantly, the implications of aerosol spread of viruses are highly unpleasant, even frightening. The air we need every minute of our lives is suspect. It is a bit like the relationship we have with food- deeply conflicted and fraught, with fears, excesses, and rituals. One has to eat, but our food is full of psychological valences, possible poisons, cultural baggage, judgement, libraries full of advice. No one really wanted to go there for air as well. So I think scientists, even those calling themselves infectious disease specialists, (of all things), settled into a comfortable conventional wisdom, that droplets were the only game in town.

But what did this say about the larger research enterprise? What did it mean that, even while medical/bio research community was sequencing genomes and penetrating into obscure and complex regions of molecular biology, we had not done, or at least not appreciated and implemented, the most basic research of public health- how infectious diseases really spread, and how to protect people from them? It constituted gross negligence by the medical research community- no two ways about it. And that appears to have caused the public at large to question what on earth they were funding. A glorious enterprise of discovery, perhaps, but one that was not very focused on actual human health.

A timeline of research/policy

• Sprawling work on airborne infection in 1955. 

• Earliest glimmer in latest pandemic, May 2020. 

• Deeper followup, October 2020.

• Even deeper followup, August 2021. Later, 2023.

• Critics still can not believe aerosol spread, November, 2022.

• Hospital HVAC requirements currently go to MERV 8, not enough.

• Current CDC guidance mentions aerosols only from "procedures", not from people, though masks are recommended.

Aerosol spread of disease requires two things- that aerosols are produced, and that the infectious microbes remain infectious while in those aerosols. The former is clear enough. We sneeze, after all. Even normal breathing creates fine aerosols. The latter is where scientific doubt has been more common, since many viruses are not armored, but have loose coats and membranes derived from our own, delicate cells. Viruses like HIV don't survive in aerosols, and don't spread that way. But it turns out that Covid viruses have a half life of about two hours in aerosols. 

The implications of that are quite stunning. It means that viruses can hang around in the air for many hours. Indoor spaces with poor ventilation- which means practically all indoor spaces- can fill up with infectious particles from one or a few infected people, and be an invisible epidemic cloud. No wonder everyone eventually got Covid. 

What to do about it? Well, the earliest aerobiology experiments on infectious disease went directly to UV light disinfection, which is highly effective, and remains so today. But UV light is dangerous to us as well as microbes, so needs to be well-shielded. As part of an air handling system, though, UV light is an excellent solution. Additional research has found that far-UV, at 222 nm, is both effective against airborne microbes and safe for human eyes and skin, creating an outstanding way to clear the air. Another approach is HEPA filtration of air, either as part of an air handling / exchange system, or as stand-alone appliances. Another is better ventilation overall, bringing in more outside air, though that has high energy costs. Lastly, there are masks, which are only partially effective, and the place no one really wants to go. But given a lack of responsibility by those in charge of our built environment, masks are the lowest common denominator- the one thing we can all do to protect ourselves and others. And not just any mask, but the N95 high-quality filtration mask or respirator.

The pandemic threw some sharp light into our public institutions. We sequenced these viruses in a hurry, but couldn't figure out how they spread. We created vaccines in record time, but wasted untold effort and expense on cleaning surfaces, erecting plexiglass shields, and demanding masking, rather than taking responsibility for guarding and cleaning public air spaces in a more holistic way. It is a disconcerting record, and there remains quite a bit yet to do.

• Poor (and personalized) policy means poor science and poor vaccines.
• Department of injustice and thought crime.
• Who needs new music?
• Putin and money.
• Another argument for public schools.
• Another biological thing that didn't exist, until it did- lymph drainage in the brain.
• No wonder no one wants to become a primary care physician.
• The Japanese ice age.