Two of the world's leading proponents of the airborne nature of COVID-19 transmission have criticized a B.C. Ministry of Health statement regarding the disease.
University of Colorado Boulder chemistry and biochemistry professor Jose-Luis Jimenez and University of Oxford primary care health sciences professor Tricia Greenhalgh both called the ministry's statement "misguided" because it didn't emphasize that airborne transmission is the main mode for catching the virus.
Jimenez was the fifth-most cited scientist in the geosciences worldwide over the past decade, according to the University of Colorado Boulder website.
"It is unbelievable that they still say that handwashing is one of the best ways to prevent spread, or that it is better than masks," Jimenez declared to the Straight. "We have known for a long time that transmission of COVID-19 through surfaces is difficult, and there are zero cases of surface transmission demonstrated to date."
On September 2, the Ministry of Health sent the statement to the Georgia Straight more than a week after the newspaper had asked the following question:
"Recent research at the University of Waterloo shows that N95 and KN95 masks block exhaled aerosol transmissions at far higher rates than surgical masks and cloth masks. Why aren’t public health officials talking much more in briefings like this about the quality of masks to protect people from contracting airborne COVID-19?”
The question came in connection with an August 25 cover story about student advocacy for stronger COVID-19 protocols.
The Ministry of Health emailed the following response:
"Most COVID-19 infections are spread from one person to another through respiratory droplets. Droplets come in a wide range of sizes and they behave differently depending on their size. Larger droplets are heavier, and they usually fall to the ground within two meters. Smaller droplets (i.e., aerosols), are lighter and they can float in the air for longer.
"Smaller droplets can collect in enclosed spaces when there is not enough fresh air. Indoor accumulation is greater when more people share a space, spend more time together, or exercise, sing, shout, or speak loudly.
"It is important to remember that masks of any type are not on their own a highly effective layer of protection against COVID-19 transmission; physical distancing, hand washing and staying at home if you are sick are the most effective ways to prevent the spread of COVID-19. Masks do not replace these actions but when worn properly can offer an extra layer of protection.
"Masks act as a filter and trap droplets so they will contribute to preventing them from being released or inhaled by the wearer. Medical N95 respirators are a type of personal protective equipment – specific equipment authorized for use as medical devices by Health Canada – and are used by healthcare workers for specific procedures that generate aerosols. These respirators must be custom fit (i.e. actual fit testing by a qualified person is required) and worn properly in order to form a tight seal to protect against aerosol transmission. They are also more expensive.
"Public health’s position is that medical N95 respirators should be reserved for use by health care providers who need protection from aerosol-generating medical procedures. Public health has provided guidance on how to choose or even make a mask that will add an extra layer of protection in addition to other measures. "
That prompted the following response from Greenhalgh: "This advice is misguided. If something floats in the air, it’s airborne and we should be using precautions that are known to prevent or reduce airborne spread. These are high-grade masks, physical distancing (most though not all airborne spread occurs within 2m), reducing time spent indoors with others, ventilation, and filtration. There is no scientific doubt that the MAIN mode of transmission of this virus is via inhalation of infected air."
Jimenez then offered his perspective.
"I fully agree with Trish," he stated. "That advice is incorrect and misguided in several ways:
"- It is unbelievable that they still say that handwashing is one of the best ways to prevent spread, or that it is better than masks. We have known for a long time that transmission of COVID-19 through surfaces is difficult, and there are zero cases of surface transmission demonstrated to date:
"- They admit aerosols (which float in the air and infect by inhalation) transmit COVID-19. But they do not follow through with the logical consequences. They seem to say that aerosols are only a problem in poorly ventilated locations. That is just wrong. Aerosols are highest in close proximity, just like if you talk with a smoker there is much more smoke in between the two of you than mixed into the room. That is the main reason why transmission in close proximity is high, and why physical distance reduces transmission (not the larger droplets falling to the ground, those are relatively unimportant for COVID-19).
"- If aerosols can infect (as they admit), good masks are a critical layer of protection, and one of the most important ones, along with distance, meeting outdoors when possible, and ventilation / filtration of indoor air. There is no longer a shortage of N95 masks, in fact there are US manufacturers that have millions in stock and can't sell them. So we believe that we should be recommending N95 for everyone who is going to be in a risky situation (e.g. in healthcare, in schools, in jobs where air is shared with others for significant periods of time etc).
"- They also seem to be out of date on aerosol-generating procedures. There are many scientific studies that show that the main aerosol generating procedures are talking, singing, shouting, coughing, and sneezing, and not the medical procedures that had been thought to be more important:
One of the people quoted in the Straight's August 25 cover story was SFU PhD student Andrew Longhurst, who agrees with the analysis of Jimenez and Greenhalgh.
"We should be providing high-efficiency masks to students, staff, workers in higher risk settings," Longhurst told the Straight. "It would help us bend the curve and maintain low rates of transmission moving forward. It's such an easy intervention (and not that expensive). Boggles my mind we'd rather people end up in ICU and cancel surgeries than implement strong NPIs [non-pharmaceutical interventions]."