Scientists now confident that COVID-19 is an Airborne Aerosol Threat
Scientists are now confident that COVID-19 is primarily an Airborne Aerosol Threat responsible for super-spreading events. They used a particle flow simulation of a restaurant that had a super-spread event in January 2020. The paper is titled: Aerosol transmission of SARS-CoV-2
Many examples of Aerosol super-spread events like the Restaurant, a Bus, a Call Center, a Choir Rehearsal, and a Zumba Group class were known since January and February. But the scientists at the CDC and the WHO were reluctant to admit COVID-19 was an airborne threat. They initially called it a surface threat and COVID-19 was spread because people didn’t wash their hands and touched their faces. They told us that cloth masks were not helpful against this threat and advised against cloth masks.
But the Call Center example had many people sharing and touching the same bathrooms and only the people sharing the same air on the same side of the building were infected. Last month the CDC admitted the Surface threat was minimal and reversed course on Cloth masks. They told us that COVID-19 is spread via large droplets larger than 5-micron aerosol particles in close range situations that could be stopped with simple homemade cloth masks. These masks, they told us, couldn’t actually keep you from being infected. But it could stop you from infecting other people because it reduced the range of your droplets so you should wear a mask to protect others within 6 feet of you.
But now that we know that COVID-19 isn’t primarily from the Surface Threat or the Droplet Threat, Cloth Masks or even medical grade Surgical Masks can’t stop the aerosol threat. NIOSH (official testing agency of the US CDC) data shows that Cloth Masks can only block around 20% of aerosol particles. Other research has shown that Surgical masks can only block around 50% of aerosol particles. Only NIOSH certified N95 masks can block 95% to 99% of aerosol particles.
Here’s a paper published by NIOSH
https://academic.oup.com/annweh/article/54/7/789/202744
We have known since 2003 from the first coronavirus outbreak of SARS that Surgical Masks don’t work against Aerosol threats. All of the Healthcare Workers who treated a SARS patient were infected with SARS despite wearing Surgical Masks.
https://www.ajicjournal.org/article/S0196-6553(07)00774-2/fulltext
In one Toronto hospital, all attending health care workers reported to be wearing “respirators” contracted severe acute respiratory syndrome (SARS) during a patient intubation. Closer examination reveals that employees were wearing surgical masks, not respirators.
There is no reason to believe that SARS-CoV-2 (AKA COVID-19) can be stopped with Surgical Masks much less Cloth Masks. The only thing that will stop COVID-19 transmission are N95 masks and Eye Protection e.g., Face Shield is needed when in close proximity to a patient. Does that mean N95 Masks for all? No, there is no way we can scale single-use N95 masks to billions of people. Even the front-line medical workers can’t get enough N95 masks.
So how do you stop this thing on a large scale? We know that COVID-19 transmission outdoors is extremely rare on the order of 1000 times less likely because viral loads diffuse rapidly. The more we can replicate outdoor air conditions the better. We know from the Bus example that all the passengers sitting next to open windows were spared COVID-19 infections.
Indoor facilities can reduce the threat greatly by opening the windows and turning up the ventilation and Air Exchange Rates with high CFM ventilation fans. In climates that are too cold or too warm, HEPA filters which filter 99% of aerosol particles must be installed. HEPA filters are not expensive but they do put a strain on the fan motors which must be upgraded. It also increases energy costs but it is a small price to pay for the safety of the occupants.
