By Robert Kernodle
Figure 1. NASA satellite image showing the two most frequent meteorological scenarios where huge quantities of viruses and bacteria are deposited in the high mountains of Sierra Nevada, Spain and at a global scale: (1) Viruses are transported by Atlantic Ocean depressions, and (2) bacteria are transported by Saharan dust intrusions.
Apparently, the fact that viruses
rein rain down on Earth by the billions-per-square-meter each day is old news. If you Bing the phrase, viruses falling from the sky, then you will retrieve page after page of links to stories that proclaim this amazing fact. Those links lead primarily to stories published online during the year 2018. These stories appeared on websites of major news outlets — where was I? — how did I miss this? I’m pretty sure that I wasn’t abducted by aliens.
The more important question might be, Why is this old news seemingly newly relevant to the present times?
Invariably, the major focus of all those 2018 internet stories was an article appearing in the Journal of the International Society for Microbial Ecology (ISME Journal), a cooperative effort between owner ISME and publisher Springer Nature:
Reche, I., D’Orta, G., Mladenov, N. et al. Deposition rates of viruses and bacteria above the atmospheric boundary layer. ISME J 12, 1154–1162 (2018). https://doi.org/10.1038/s41396-017-0042-4
The main thrust of this article was that “aerosolization of soil-dust and organic aggregates in sea spray facilitates the long-range transport of bacteria, and likely viruses, across the free atmosphere.”
The word, aerosolization, is defined as the process or act of converting some physical substance into the form of particles small and light enough to be carried on the air (i.e. into an aerosol).
From the body of the article:
We quantified the wet and dry deposition of (free and attached) viruses and bacteria above the atmospheric boundary layer at the Observatory (OSN) and Veleta Peak (VSN) in Spain, and demonstrated that in each square meter, tens of millions of bacteria and billions of viruses are deposited each day.
The phrase, atmospheric boundary layer, for those (like me) unfamiliar with the concept), is also known as the planetary boundary layer. What is it?
According to A. Molod, H. Salmun, M. Dempsey (2015). Estimating Planetary Boundary Layer Heights from NOAA Profiler Network Wind Profiler Data, Journal of Atmospheric and Oceanic Technology, 32(9) https://journals.ametsoc.org/doi/10.1175/JTECH-D-14-00155.1
The planetary boundary layer (PBL) is the shallow layer of the troposphere nearest to the Earth’s surface that, particularly over land, exhibits a diurnal variation due to the exchange of energy and momentum between the surface and the atmosphere. The depth of the PBL can range from less than one hundred meters to several kilometers. Knowledge of the PBL depth and its fluctuations in time are also essential for the estimation of the transport of atmospheric constituents, and in particular to estimate the terms in the atmospheric carbon budget.
Figure 2. Visualization of the planetary boundary layer or atmospheric boundary layer, from www.skybrary.aero
The authors of the ISME paper, thus, confidently state that long-range transport of viruses and bacteria occur, but admit that there are many uncertainties associated with deposition rates of viruses and bacteria. Nonetheless, they claim to demonstrate in their study that, above the atmospheric boundary layer,
downward flux of viruses ranged from 260,000,000 to greater than 7,000,000,000 per square meter per day. These deposition rates, they further assert, were 9 to 461 times greater than the rates for bacteria, which ranged from 3,000,000 to greater than 80,000,000 per square meter per day.
So, viruses can be carried on the air of Earth’s atmosphere (billions and billions of them), and they can be carried long distances in this manner, say, from one continent to another. Should this terrify us? Before approaching such a question, let’s consider some basics, like how many types of viruses there are, and how prolific viruses are on the planet.
In plowing through the internet, looking for an answer to the question of how many different viruses there are, I haven’t found a clear and straightforward answer. As near as I can tell, we really do not know how many there are, but the number is huge, which means that the venture of discovering new viruses seems to be an active scientific endeavor.
Also, given their large number and prolific presence on the planet, viruses mutate all the time, thus adding more new types to the already vast collection. And then there are the labs that experiment with viruses — who knows how many different human-created types are out there that ordinary people do not know about? [but that’s another topic]
A statement by Berliner et al. — in Aaron J. Berliner, Tomohiro Mochizuki, and Kenneth M. Stedman (2018). Astrovirology: Viruses at Large in the Universe, Astrobiology, Volume 18, Number 2
summarizes it nicely:
Viruses are the most abundant biological entities on modern Earth. They are highly diverse both in structure and genomic sequence, play critical roles in evolution, strongly influence terrain biogeochemistry, and are believed to have played important roles in the origin and evolution of life.
The takeaway from this statement is that humans probably would not exist without viruses. In other words, one of the reasons for our being is also one of the reasons for our dying. Life is strange this way — replete with seeming contradictions, or, at least, oppositions that tend to balance one another.
Let’s incorporate this insight, as we get back to the question of whether virus transport in Earth’s atmosphere should terrify us. Consider these key statements from the Reche et al article:
Despite the high genetic diversity within viral communities, the observation has been repeatedly made that identical or nearly identical virus sequences can be found in widely separated environments that are environmentally very different.
Viruses and bacteria are usually not air-dispersed as free particles, but are attached to soil-dust or marine organic aggregates.
Based on what could be detached by washing in buffer and mechanical forces, ~69% of viruses and ~97% of bacteria deposited from the atmosphere were attached to dust or organic aggregates.
After reading those statements, my mind goes to particulate pollution and possible increased opportunity for viruses to attach to these particulates. Next, I think of China, New York, and the major polluted parts of Italy and Spain, as these places seemingly suffer the devastation of the SARS-CoV-2 virus. But then I have to keep in mind that most viruses are not harmful to humans — they are fundamental features of the planet, which would make them integral parts of the proverbial natural order.
Next, I have to wonder what are the statistical odds that a virus harmful to humans is a virus that could hitch a ride on dust or sea spray or air pollution (if this is even possible).
And here is where my ignorance shows itself — I have no idea. That’s one reason I wrote this article — to raise the question and hopefully gain more knowledge from insightful people who might help with an answer.
Figure 3. T4 bacteriophage joins artist, Luis Falero’s 1878 painting, “Vision Of Faust”, in a digital manipulation by Robert Kernodle
In the meantime, I have probed deeper into the philosophical question of death itself, in asking this: If death is a part of life, and viruses are natural parts of life as we know it, then is a death caused by a virus a death by “natural causes”? What exactly is a death by natural causes? What exactly is death by old age? Are the old who are dying allegedly because of the SARS-CoV-2 virus undergoing the dying process of old age? Is that part of what it means to die of old age?
Is our current fear of COVID-19 a fear spawned of childish fragmentation from reality, where we have grown so accustomed to the protections and comforts of our modern civilizations that we have lost touch with survival of the fittest? — during an era when so many people are physically unfit?
Is our current fear a result of an unprecedented number of people coming to terms with the very idea of death for the first time? — young people (constantly interacting electronically), wanting to live forever, watching older people succumb to a seemingly routine process?
Is our current fear, therefore, irrational, as it causes leaders to halt the operation of civilization, in a panic to protect life? I certainly have my own answer to this last question, which is yes — an answer that I have held onto, since day one of the first shutdown.