Thread by @jeffgilchrist

COVID-19: Impact of air filtration in hospitals

This very interesting study shows COVID-19 virus along with other bacterial and fungal pathogens were removed from UK hospital wards by air filtration ( medrxiv.org/content/10.110… ). 🧵1/

Researchers measured pathogen levels for 5 days to set a baseline, then activated the filtration system for 5 days, and then took measurements for 5 days again after the filtration system was turned off in both a COVID-19 hospital ward and ICU. 2/

They detected airborne COVID-19 virus in the ward on all 5 days before filtration activation, but none of the 5 days when the filter was active, then they detected COVID-19 virus again for 4 of the 5 days when the system was turned off again. 3/

One thing I keep saying is that investing in improving ventilation and filtration not only helps with this pandemic but improves the air for everything else and will continue to provide ongoing benefits. 4/

The study found that filtration significantly reduced the burden of other microbial bioaerosols in the ward with 48 pathogens detected before filtration and only 2 detected after. In the ICU there were 45 pathogens detected before and 5 detected after. 5/

You can see in the image all of the pathogens detected when the air filter was off and the difference when the air filter was on. In the ward the fungi Candida spp. was still detected while the air filter was running. 6/

IPAC specialists seem to focus a lot on droplets and surface (fomite) contamination but this provides yet another example why they need to also focus on the air. You can see what the filtration units look like here ( ). 7/

COVID-19 virus is circulating in a hospital ward within aerosols > 1 uM. Aerosols of 1-4 uM are likely a key vehicle for COVID-19 transmission as they can remain airborne for a prolonged period of time, can easily be breathed in, and can deposit deep in people's airways. 8/

Hospitals are still providing regular procedure masks to health care workers not designed to protect the wearer against aerosol transmission. 9/

In many cases, stronger protection such as N95 or elastomeric respirators are only provided in certain circumstances such as around patients who are undergoing aerosol generating procedures (AGP). 10/

Ironically, recent studies have shown that exertional respiratory activities such as talking, exercise, shouting, coughing and singing actually produce significantly more aerosol particles than many AGP respiratory therapies on maximal settings ( …-publications.onlinelibrary.wiley.com/doi/10.1111/an… ). 11/

These data are consistent with the observations in this study as well. The researchers actually found that removing aerosol particles may be *more* important in conventional wards than in well defined "aerosol risk areas". 12/

A low burden of COVID-19 found in the ICU air and the higher level of aerosol protection worn by ICU staff may explain why staff in ICUs appear to be at significantly lower risk of becoming infected than those working on regular wards ( thorax.bmj.com/content/75/12/… ). 13/

By the time people infected with COVID-19 end up in the ICU, their viral load is likely significantly lower and less likely to still be infectious than those just admitted to regular hospital wards. 14/

Proper protection should be provided to all health care workers in the form of better masks and better ventilation/filtration, especially those that may come in contact with COVID-19 infected patients. 15/

I was in a hospital yesterday for a lab test, and the health care worker asked me where I got my masks since she could see mine looked much more comfortable, was easier to talk in without the mask constantly touching my lips, and provided better protection. 16/

She was wearing a standard procedure mask and also admitted that she would prefer a mask where people couldn't easily tell the expression on her face sometimes.😀 17/

It is a sad state when the general public is walking into hospitals with better protection than what the workers are being provided. If you are curious, I use the Canadian made and readily available FN-N95-508 respirator from Canada Strong Masks ( canadastrongmasks.ca ). 18/

I was grateful at the hospital entrance where they were screening people that they allowed me to keep my N95 mask when they found out it was new instead of forcing me to take it off and use one of their procedure masks which would have provided me with less protection. 19/