Victor Luca, 12-Jan-21.
Early on in the COVID-19 pandemic there was considerable denial regarding the benefits of wearing face masks in the fight against the pandemic on the part of our Ministry of Health (MoH) who simply toed the WHO and CDC line. In fact, it took our MoH five months to finally start recommending the use of face masks.
Yet the evidence for airborne transmission, and the utility of face masks, was staring everyone in the face (so to speak) since the beginning of the pandemic.
When an infected person sneezes or coughs (or even speaks and breaths), liquid droplets carrying small virus particles are expelled from the mouth and nose. SARS-CoV-2 is only a small particle measuring about 100-200 nm in diameter (0.1-0.2 microns). Between one and two hundred million SARS-CoV-2 particles could fit on the head of a pin.
Depending on how hard you cough, sneeze, speak and even breath, plus other factors, some of the liquid droplets expelled during these processes may be relatively large (10-100 micron) and fall to the ground in close proximity to the infected person. Other droplets may be so small that they float in the air. As the tiny droplets are expelled and travel through the air, the water that caries the virus particles dries leaving the small SARS-CoV-2 virions and other components of saliva and mucous suspended. Being tiny and of low density the SARS-CoV-2 particles can stay aloft for long periods of time. Facilitated by air currents they can travel large distances. These particles can be breathed in directly and drawn deep into the respiratory tract.
One could deduce from relatively simple physical-chemical principles that this is the case. The science of aerosols is well developed.
From before the onset of the pandemic there were plenty of reports available in the scientific literature on the airborne transmission of diseases and the virtues of mask wearing. And yet it took a lot of folk like our MoH five months to bring themselves to recommend mask use. Why they were so slow, I do not know. Sure, the case for this particular virus was not totally iron-clad because, even if the virus is airborne, we were not totally sure how much the infectious dose was for this virus. The infectious dose is how much of the virus do you need to incorporate in order to get COVID-19.
However, it has been well known for quite some time that many other viral diseases, including measles & influenza A are airborne, meaning that the virus particles are easily transported in air. The science in the case of these diseases, which have similarly sized virus particles as COVID-19 is settled. There is nothing to argue about here.
Source: Gandhi and Marr, Uniting Infectious Disease and Physical Science Principles on the Importance of Face Masksfor COVID-19, Med (2020), https://doi.org/10.1016/j.medj.2020.12.008
A properly fitting mask acts as an effect barrier between you, the wearer, and the airborne virus particles. There is lots of science behind the fabrication of face masks. Some face masks, like the N95 masks, took 10 years to develop in order to effectively filter small particles.
In a commentary published on 16-Mar-20, Lisa Brosseau, a leading expert on respiratory protection and infectious diseases and Emeritus Professor (retired) from the University of Illinois at Chicago, and presently based at the Center for Infectious Disease Research & Policy (CIDRP) cautioned folk to be guided by the science when it came to making determinations on SARS-CoV-2 transmission and the utility of face masks.
Turns out she was right, and the evidence was always right in front of our noses. But not all face masks are the same as I already mentioned.
Aside from face masks limiting the ejection of virus from infected person, and affording protection to the wearer from infected individuals, there is evidence that a mask may perform a function not unlike that of vaccination. The theory goes that a mask limits the amount of virus that can be inhaled by the wearer. Since dose is important in determining disease severity a small dose of virus is likely to not overwhelm the immune system but rather serves to train the immune system in similar fashion to a vaccine. In other words, a small dose generates an immune response without overwhelming the system.
There is evidence to support this assertion.