The SARS-COV-2 [1] virus pandemic that started in late 2019 and took over the planet in 2020 has been the big news of late. I don't think there is anyone on the planet who does not know about the virus and its impact on the world.
XPrize [2] held a competition in 2020 called the XPrize Pandemic Response Challenge [3]. I competed in this challenge and made it to the final. The competition concerned itself with creating two kinds of models, one to predict mortality and morbidity, and another to predict intervention policy. The first round was the prediction portion where my model performed quite well. The model I wrote used some anecdotal knowledge about prevention and risk as well as some research topics that were emerging in 2020.
Out of this competition there were some interesting anecdotal observations about virus transmission.
- Masks could be ineffective. When you respirate through a mask in an area that has elevated concentrations of the Covid-19 virus, the particles hosting the virions will collect on your mask. These particles are huge compared to the 90nm - 140nm size of the virus [4] so they effectively stop the virus from passing through to 300nm holes in your mask [5,6]. Yet, if you do not clean the mask, or change masks, then these particles will "build up" and create a living biofilm on your mask. That biofilm will then pass virions through the 300nm holes in the mask and you will eventually develop a Covid-19 infection.
- Atmospheric inversion is not your friend. One of the participants in the competition was from Mila in Canada. He had a theory about environmental temperature being an influencing factor for morbidity. I asked for an explanation on this but did not get one. My explanation is about atmospheric inversion. When a group of humans congregate (3 or more) into a huddle where the ambient temperature is 65F or cooler, that huddle will start to warm itself. The warming of the air around the humans will create a pressure bubble that will simulate the atmospheric inversion phenomenon. This inversion will create a bubble where virion transport particles, such as water vapor and dust, can become suspended in the warming air and thus increase the mean free path length of a virion to infected.
- Fans and coughers make for bad environment control. A South Korean study reported that a person who sat in front of a fan and was coughing had spread their infection on to other people in the same room who were down-wind of this fan [7]. This goes back to bullet 2 above where the mean free path to infection is increased because of atmospheric charging. In this case, the excess fan pressure was the charging condition that elevated the infection risk.
- Fashion played a role in anti-mask sentiment. My competition model used Twitter sentiment about covid-19 infections, mask wearing, and conspiracies, as one of the features in the regression predictor. This feature was not helpful in the prediction model, but it did elucidate some interesting trends early in 2020. I noticed, anecdotally, that when posters would lament the fashion-negatives about mask wearing, then followers and fans would star and repost those lamentations more often than of positive mask postings. Nobody looks clever wearing a carpenter's dust mask, but today's mask fashion options have certainly removed most of this stigma.
- Testing was the key prediction feature. In my model that predicted the outbreak in India in April of 2021, the amount of testing done by the country was a critical feature. Countries that were not testing enough were experiencing outbreaks at an uncontrolled rate. India, at its first wave, responded remarkably to controls. This confused me quite a bit given that population density and mean distance to hospital were key factors in morbidity predictions, because India has poor population density and even poorer mean hospital distance. How did it "control" the infection? By not testing in the high risk areas. Once the upper-caste Indians had experienced the first wave, it appeared as if the government had stopped testing the lower-caste areas and wrote off the infection as "done." Brazil had performed similarly and resulted in an equal catastrophic resurgence of infected.
- 30 minute rule was life. There was a great paper [8] that determined this 30 minute rule for effective infection risk. If you limited your exposure to less than 30 minutes in any situation, the you would have a lower risk of covid-19 morbidity. This doesn't mean you have zero risk. Rather, this means you are mitigating your risk by lowering your time of exposure to less than 30 minutes. Obey the 30 minute rule and you have a better chance of not getting infected.
- No shared food. This was the least scientific of the observations because in almost every situation of cluster morbidity there was a shared food component. There is no evidence that esophageal ingestion of the virus can cause an infection, but the cofactors of shared food environments lend to higher risk of infection. For instance, people talk more and respirate more heavily around food tables. People also linger more around the food table, thus breaking the 30 minute rule of #6.
- Gyms are a hot spot for infection. In the exercise gym there are fans blowing virions at your face, there are heavy breathers respirating large droplets of water carrying virions in high concentration, and there is dust blowing around carrying those virions. If you had to visit a gym during 2020 then you likely developed covid-19. The best advice I have for gym-goers is to avoid fans, and change your mask every 10 minutes. Bring 6 masks with you and every 10 minutes, like clockwork, put the used one in your Zip-Loc bag and put on a fresh one. Then at home, clean those masks (see #9).
- Cleaning a mask means exposing it to sunlight for 15 minutes [9]. UV radiation can destroy most everything, and little viruses are no exception. You need to wash the mask for 30 seconds, then take it outside and expose the outside of the mask (not the face side) to direct sunlight for no less than 15 minutes. I preferred to leave the masks outside for several hours. Not only does UV neutralize the mask, but oxidation will occur of those broken down proteins thus neutralizing their effectiveness. You should hang with your mask for 30 minutes outside too, just to get some sun and Vitamin-D. That'll help your disposition during this quarantine.
- Air blowing outside is not a vector. The likelihood of your body producing a negative pressure condition strong enough to ingest virions outside when the wind blows 10 mph or greater is incredibly low. So low, that you will not get the virus, even if someone is coughing up-wind of you. Just remember to obey #2 and #6 to ensure that your risk is mitigated properly. Don't congregate with people because they will shield you from that wind and create the bubble.
[1] Zheng J. SARS-CoV-2: an Emerging Coronavirus that Causes a Global Threat. Int J Biol Sci. 2020;16(10):1678-1685. Published 2020 Mar 15. doi:10.7150/ijbs.45053
[2] xprize.org
[3] https://www.xprize.org/challenge/pandemicresponse
[4] Bar-On, Yinon M et al. “SARS-CoV-2 (COVID-19) by the numbers.” eLife vol. 9 e57309. 2 Apr. 2020, doi:10.7554/eLife.57309
[5] https://blogs.cdc.gov/niosh-science-blog/2021/04/23/bfc-standard
[6] https://www.ll.mit.edu/news/tests-verify-if-uncertified-n95-masks-are-effective
[7] https://www.latimes.com/world-nation/story/2020-12-09/five-minutes-from-20-feet-away-south-korean-study-shows-perils-of-indoor-dining-for-covid-19
[8] Leung, Nancy H., et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine, 2020; Volume 216, pp 676-680.
[9] https://onlinelibrary.wiley.com/doi/10.1111/php.13293