Dr Victor Luca
Published in The Beacon 21-Jan-22
Two years have now passed since COVID-19 first disrupted our lives. On the 8th of April 2020, shortly after the declaration of the pandemic by the WHO, I published an article in The Beacon newspaper advising readers that more than a month of intense bibliographic research had convinced me that airborne transmission was an important factor in the spread the COVID-19. Like the CDC and the WHO, our health authorities had regarded this mode of transmission as subordinate to other modes including contact, droplet and fecal-oral.
Droplet transmission occurs when large (>10 micron) virus-loaded fluid droplets expelled from the upper respiratory track of an infected individual enter a recipients airways. Airborne transmission refers to much smaller liquid droplets carrying virus particles (see Figure) that are generated by an infected person in the act of coughing, sneezing, shouting, speaking and even breathing and which can remain suspended in air indefinitely and travel large distances. Smoke aerosol particles expelled by a cigarette smoker are a good analogy. Detailed knowledge of how the virus is transmitted from person-to-person is important in defining pandemic response policy.
I came to my conclusion of the importance of airborne transmission by observing that the science was settled on the role of airborne transmission for other bacterial and viral infectious diseases, especially influenza, and by noting that influenza and SARS-CoV-2 virus particles are similar in dimension, density and morphology.
I also mentioned in subsequent articles that like radioprotection, COVID-19 risk reduction is all about distance, time, and shielding. You limit your distance to the source (the infected individual), the duration of exposure and put something between yourself and the pathogen. In other words a face mask. The usefulness of facemasks in limiting the spread of a respiratory infectious disease is something they had already figured out in 1918, well before anyone knew what a virus was. In my 8-Apr-21 article I recommended the use of the so-called N95 respirator face masks as the preferred option to limit the infected from expelling virus particles and the uninfected from inhaling them.
So far we have done a reasonable job of keeping COVID-19 out of New Zealand, and so have spared our population much pain and suffering and the sight of pain and suffering. In the meantime, science has delivered new tools to fight this virus in the form of effective, robust and safe vaccines. After a shaky start we managed to secure and roll out the Pfizer-BioNTech mRNA vaccines to the bulk of the population. Although the mRNA-based vaccine class was built on 30 years of underpinning research, I was still delighted and relieved to see the technology rolled out at mass-scale so quickly. This shows what we humans can do when push comes to shove.
More recently Pfizer has developed a game-changing pill known as Paxlovid that studies and trial data is showing to be highly effective (ca. 90%) at preventing hospitalization if taken soon after symptom onset. The medication has now received Emergency Use Authorization by the US Food & Drug Administration. However, the synthesis of this medication is complex and so mass-production will probably not be a cake walk.
The new variant, omicron, is clearly many times more infectious than the delta variant that it has swiftly displaced in many parts of the world. We will not be able to be kept it out forever unless we wish to remain an isolated island in the middle of the pacific. When omicron hits us, and experts are telling us that we are weeks away, our fragile health system, which is seriously challenged at the best of times, will be challenged like it has never been challenged before. Protection of the health system is the main reason we have opted for elimination and suppression strategies. Sooner or later however, we will have to face the music.
In the face of an impending omicron wave, I believe that there is a need to double down on all measures that can keep people out of hospital and that includes improving our masking practices. After vaccines and anti-viral drugs, distance, reduced exposure time and masks are our next lines of defense. Although any well-fitting mask is better than nothing, the N95 respirator masks have been developed to fit better and filter small particles with high efficiency (95% of particles smaller than 0.6 mircon). These masks have been clearly shown to offer superior protection against SARS-CoV-2 infection and onward transmission.
Folk that are in mask denial should ask the surgeons and surgery staff not to wear theirs next time they go under the knife. They could also ask their mechanic to leave the air filter out when next they get their vehicles serviced and see how they get on.
It is important to emphasize that masks should fit properly over the nose and mouth and not allow entry of air from gaps between the mask and face. Unlike other masks, N95 respirator masks are designed not to contact the mouth and to fit snugly around the nose. There has been significant science and technology behind the 10 year development of the genuine N95 mask. They can be used multiple times if they are decontaminated appropriately between uses. Perhaps one of the best decontamination methods is to simply put the mask aside for 10 days after which the virus will become inactivated. After removing a used mask you should try to avoid touching the mask surface with your hands as the mask should be treated as a contaminated object. I recently purchased a bunch of Chinese-made KN95 masks from Bunnings for 20 cents each. The NIOSH-certified N95 masks will be more expensive but they offer greater security that they meet the standards. Also, beware of counterfeit masks.
The omicron variant is a demonstration of the evolutionary potential of this pathogen and emphasizes the need that exists to squash the pandemic as early as possible. We needed to clip the wings of this virus in order to reduce its opportunity to evolve and that requires eliminating the virus from all countries not just the wealthy ones. There is no room for vaccine nationalism in this dangerous game we are playing. The latest data is suggesting that omicron shows vaccine evasion.
If you do not understand what I am saying in this article, or just want more information, please don’t hesitate to get in contact.
References
Asadi et al., Time to upgrade from cloth and surgical masks to respirators? Your questions answered. The Conversation, 18-Jan-22
Clase et al., Are two cloth masks better than one for preventing the spread of COVID-19? The Conversation. 12-Feb-21.
Fennelly et al., Particle sizes of infectious aerosols: Implications for infection control. The Lancet 2020, 8(9), 914-924.
Fox-Lewis A, Williamson F, Harrower J, Ren X, Sonder GJB, McNeill A, et al. Airborne transmission of SARS-CoV-2 Delta variant within tightly monitored isolation facility, New Zealand (Aotearoa). Emerg. Infect. Dis. 2022. https://doi.org/10.3201/eid2803.212318
Juang & Tsai. N95 respirator cleaning and reuse methods proposed by the inventor of the N95 mask. J. Emergency Med. 2020, 58(5), 817.
Ogbuoji et al., Advanced Research and Development of Face Masks and Respirators Pre and Post the Coronavirus Disease 2019 (COVID-19) Pandemic: A Critical Review. Polymers2021, 13(12), 1998.
Scheuch et al., Breathing is enough for the spread of influenza and SARS-CoV-2. J. Aerosol. Med. Pulmonary Drug Delivery 2020, 33, 230.
7-Jul-20.
Yi et al., Numerical simulation of virus diffusion in facemask during breathing cycles. Int. J. Heat. Mass. Trans. 2005, 48, 4229.
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