COVID
IT’S NOT COOTIES!
THE COMMON SENSE BIOPHYSICS OF COVID 19 TRANSMISSION
COVID 19 spreads as an infectious aerosol, therefore the danger of infection is from inhaling enough exhaled breath from an infected person to constitute a infectious dose.
THE INFECTIOUS AGENT – is not the virus itself. A lone virus is so small that no mask would even slow it down. Viruses fill every speck of our environment from the bottom of the ocean to the top of the atmosphere, even in a sample taken by the space shuttle. With each breath, you take hundreds of them into your lower respiratory system, where they have direct access to your blood stream. As a result, viruses can pass in and out of us without consequence. Even viruses that cause diseases which you have never had may be found in your blood; and a nasal swab can sometimes test positive for COVID 19 that was simply trapped in your nose, where it gets stuck in mucous and cannot grow or infect. The infectious agent is not the virus - it is a fog of tiny virus-containing mucous balls.
TARGET TISSUE - Microbes have a property called tropism - they need just the right microenvironment, usually in the form of a target tissue, to replicate successfully. In the early COVID variants, the target tissue was the lower respiratory system, where it prevented oxygenation and had direct access to the blood stream, enabling it to spread all over the body. However, it was less transmissable than omicron, because nothing larger than 5 microns in size has access to the lower respiratory system. In the omicron variants, the target tissue is the upper respiratory system, where both smaller and larger infectious mucous balls can still get in and cause infection, but the infection is less deadly, because it does not prevent oxygenation.1-2
If you want to see what the infectious fog looks like, exhale at close range onto a mirror. You make a fog of tiny droplets, mostly water, with an average size of about a micron. The fog only lasts about 10 seconds, because water droplets dry out and disappear quickly.7 However, the fog of an infected person also has tiny virus-containing mucous balls which remain on the mirror, even though they are too small to see. Each infectious mucous ball is a micro-ecosystem that depends on water, like all ecosystems. It can survive a day or two on the mirror while its bed of mucous protects it from drying out. In fact, its bed of mucous is so protective that it can survive digestive enzymes, because intact virus can be easily found in wastewater. Mucous is what protects the digestive tract from its own enzymes.
INHALATION - The fastest way to get infected is by close talking, like when you can feel the warmth of the other person’s breath. That’s why Italians and New Yorkers (in your face!) got hit so hard. The virus also gets shed in feces and probably also in farts, so the aerosol created by a flushing toilet can also be infectious.6 The six foot rule came from a 2007 study of the behavior of respiratory droplets that are large enough to fall out of the air within six feet.3 More recent studies showed that the plume from a cough contains many large droplets that travel more than 6 feet as well as smaller droplets that can float in the air for hours.4-5 Therefore, one foot of distance between people is safe outside in a wind; but in a room with stagnant air, there is no safe distance, there is only a safe amount of time. In a room with no windows open, the 5% escape of breath from a person wearing an N95 mask could fill the room with enough infectious fog to infect another person wearing an N95 mask from the 5% of breath they inhale, therefore ventilation may be even more important than mask wearing. Obviously the safest option is to do both.
PREVENTION - When outside, even a slight breeze disperses the fog quickly. Vulnerable people upwind. When inside, high ceilings, open windows, and fans can disperse the infectious fog.
TOUCH - is much less dangerous, because any infectious agent transmitted by touch still needs to be aerosolized to get inhaled to reach the target tissues. Touch can transmit partially dried up mucous balls known as “droplet nuclei”. In Wuhan, researchers reported finding “droplet nuclei” only .25 microns in size.8 On porous surfaces such as clothes, these droplet nuclei can stay viable for about a day before they dry out and die. On non-porous surfaces like plastic and metal, they can stay viable for slightly longer; and on wet and slightly salty surfaces, like meat, fish, sweaty skin, your eyes, or your mucous membranes; they can probably stay viable for much longer, because viruses have no metabolism to fill them up with toxic metabolic by-products. A person who is exhaling infectious mucous balls all day and night can accumulate these droplet nuclei on surfaces exposed to their breath. However, to get these infectious agents to their target tissues in your lungs, a sufficient quantity of them must be inhaled.
KISSING – is not as dangerous as people assume. In fact, the most dangerous thing about kissing is probably the intense face to face breathing that usually accompanies it. The coronavirus does not grow in saliva or nasal epithelium, and it cannot climb down from the mouth or nose on a wall of mucous that is constantly moving upward at about 1mm per minute due to the beating of the cilia, because viruses have no motility. The only way the virus can get down from your nose or mouth into the target tissues in your lungs is by inhaling with enough force to pull the tiny mucous balls off the wet surfaces lining your mouth or nose, which would require overcoming the forces of cohesion that stick wet things together.
SEX – is dangerous primarily because it can create a lot of deep breath, so it has to be well ventilated, but COVID 19 is unlikely to spread through body fluids. It can probably stay viable in body fluids for a long time, because it will not dry out there, but it does not grow there. Rubbing of skin can transmit droplet nuclei between people, which could later be inhaled, and slapping skin can aerosolize them.
HOT TUBS AND STEAM ROOMS - are relatively safe, because the droplets in the exhaled breath from an infected person would have difficulty crossing a dense fog of water droplets without a large percentage of them merging with the water droplets and becoming too large and hypotonic to be inhaled into the lower respiratory system.
CLEANING AGENTS – have mostly been directed at the capsid or lipid envelope of the virus, which they cannot access through their mucous coverings. Mucous can withstand soap and alcohol, but it cannot withstand alkalai; because it is held together by disulfide bonds, which get broken easily by strong bases; such as bleach, ammonia, sodium hydroxide (lye), sodium carbonate, limestone, and sodium bicarbonate (baking soda).
POLITICS - The first outbreak occurred in China, where it was tackled by a very modern medical system, which has one clear chain of command, with one person at the top of that chain, to whom everyone reports loyally. By February 2020, they had brought the first outbreak under control. At that point, the person at the top of that command chain knew more about COVID than anyone in the world. He may be willing to lie and cheat; but he was proud of controlling the outbreak, he wanted to be accepted by the world community, and he had no reason to lie to our president or the rest of the world at that time about COVID. He told Trump, “You catch it from the breath.” At that point, we were still being told to keep washing our hands and using hand sanitizer rather than to use masks. While we were waiting for science to give us answers, we were overlooking common sense. Covid is a respiratory virus, and respiratory viruses spread by inhalation rather than touch. Education is more effective than legislation, because people don't like being told what to do.
FOOTNOTES
1) Tellier R. Review of aerosol transmission of influenza A in human beings. Lancet Infect Dis 2007;7:257-265.
2)Justin Morgenstern, "Aerosols, Droplets, and Airborne Spread: Everything you could possibly want to know", First10EM blog, April 6, 2020
3) Xie X, Li Y, Chwang AT, Ho PL, Seto WH. How far droplets can move in indoor environments–revisiting the Wells evaporation-falling curve. Indoor Air. 2007;17(3):211–225
4) Loh NW, Tan Y, Taculod J, et al.The impact of high-flow nasal cannula (HFNC) on coughing distance: implications on its use during the novel coronavirus disease outbreak. J Can Anesth 67, 893–894 (2020).
5) Tellier R, Li Y, Cowling BJ, Tang JW. Recognition of aerosol transmission of infectious agents: a commentary. BMC Infectious Diseases (2019) 19:101.
6) Johnson DL, Mead, KR, Lynch RA, et al. Lifting the lid on toilet plume aerosol: a literature review with suggestions for future research. Am J infection control 2013;41(3):254-58.
7) Papineni RS, Rosenthal FS. The size distribution of droplets in the exhaled breath of healthy human subjects. J Aerosol Med. 1997;10(2):105–116.
8) Liu Y, Ning Z, Chen Y, et al. Aerodynamic characteristics and RNA concentrations of SARS-CoV-2 aerosol in Wuhan hospitals during COVID-19 outbreak. BioRxiv 2020, Mar 10.