I note recent queries re the efficacy of portable HEPA filtration in schools. It might help to know that HEPA works wonders in hospital settings. See published studies below. There is no reason to think they should not be used in schools to curb the spread of SARS-CoV-2.
"Aerosols rapidly travelled from the patient room into other parts of the ward. Air cleaners were effective in increasing the clearance of aerosols from the air in clinical spaces and reducing their spread to other areas. With 2 small domestic air cleaners in a...
...single patient room of a hospital ward, 99% of aerosols could be cleared within 5.5 minutes." cambridge.org/core/journals/…
"best location of a single portable air purifier unit is inside the isolation room & near the patient's bed. The outcome of this paper can be widely used by hospital facilities managers when attempting to retrofit...
a general patient room into an airborne infection isolation room"
"Using two HEPA air cleaners close to the aerosol source reduced the aerosol exposure of the uninfected participants and speaker by up to 65%. A combination of HEPA air cleaners and universal masking reduced exposure by up to 90%."
Strategic placement can optimize performance. Best for decision makers to get the HEPA units into the school buildings first, then consult an engineer for placement strategy relative to the area/room specs. This should not stall anything. Get the HEPA cleaners into the buildings.
A building engineer can very easily tell you where best to place the HEPA cleaners. If you are muddling over this before moving forward, you are wasting time. Get the HEPA cleaners into the buildings.
If you are worried to waste $ based on the notion that respiratory aerosols might not carry SARS-CoV-2, know that they do. We measured it: medrxiv.org/content/10.110…
Surprised to see 85% of the viral RNA load was detected in fine aerosols (≤5μm) compared to coarse aerosols (>5μm).
Should point out that it is not my intention to distract from current efforts to improve building ventilation. Far from my intent! Proper ventilation is VERY important, yet lacking in schools. HEPA helps when HVAC can’t be fixed to the level that is needed in this emergency.
Adding in some guidance here from @JHSPH_CHS. See recommendation number 2 and attached thread regarding HEPA filtration units in schools. This was released in the spring. Are the units in the buildings yet? If no, time to pick up the pace!

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More from @drkristenkc

27 Apr
What happens when your "high standard of proof" is so high that it cannot be reached in a reasonable amount of time before implementing common sense infection prevention strategies for a pandemic respiratory virus?

Global demise.

That's what.
The very thing these authors are proposing, is the very thing that prevented the acknowledgment and control of aerosol transmission of SARS-CoV-2.

This "hierarchy" excludes epidemiology, occupational health, engineering, and aerosol science.

It is biased and needs revised.
These "levels" (sort of) make sense for "proving" causality in the basic sciences, but they should NOT be required before taking action.

They are proposing to do what they have already done, and look where that got us!
Read 18 tweets
23 Apr
In October 2008, researchers did a study like this in Ontario for seasonal influenza and literally stopped the study because of the 2009 influenza pandemic. Last year, the same PI was granted permission to do this during a far worse respiratory virus pandemic. What is going on?
Apparently, this is the type of research that is allowed to happen when the importance of infection through inhalation is underemphasized.
It is why systematic reviews on this topic are carefully vetted by multidisciplinary teams, such that they are not used to justify inadequate PPE for workers. 👍 thelancet.com/journals/lance…
Read 7 tweets
21 Apr
In early 2020, we detected airborne SARS-CoV-2 in COVID-19 patient rooms (in the absence of superficial aerosol generating procedures) in a Singapore hospital. We alerted WHO and others immediately and scrambled to get the word out in a preprint on April 9, 2020. Read on...
On April 15, 2020, Singapore (where I live/work) mandated masks for everyone outside their home. Smart move. Given past experience (7 years researching airborne transmission of viruses, now 8), I could see early on that this virus was transmissible through aerosols. So, masks..👍
The simple fact that this was a *respiratory* virus causing a pandemic was really all the information that was needed. Despite this, I knew at least *some* folks would argue for evidence of viable virus in air, but we did not have permission to do the cultures yet.
Read 23 tweets

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