On Jun 16, 2020, at 11:43 AM, Frazier, Alicia S <ASFrazier**At_Symbol_Here**MARATHONPETROLEUM.COM> wrote:

I have seen papers that say that the virus can aerosolize and papers that say it cannot.  Some suggest it can do a combination of both.  Some of the studies seem poorly designed and some had not been peer reviewed.   I have not seen anything that I consider definitive either way. To my knowledge there has been no definitive virus half-life in air determined either.    
We do know the size range of the virus particulate, one link is below, have seen others that suggest they can range bigger than the 90nm cited below but those I have read start the virus range at around 70nm and go up to about 250nm (As a comparison TB bacteria is at the 3000-4000nm range; measles  50-1000nm range, Ebola 600-1400nm range.)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7045880/

Being so tiny is one reason why a virus spreads easily.  Even if the virus is entrained in a droplet, those droplets at a certain size behave like little particulate matter in air.   

You asked for an opinion so here goes:   In well circulated air there is probably not an issue with enough concentration of viable virus to receive an infectious dose.  Like walking past someone outdoors or even at a store.   It seems to be when people are in very close proximity with prolonged contact in homes or in tight quarters such as nursing homes, prisons or ships that infections are most common.    This suggests to me that it could aerosolize because in those places the air is recirculating and the virus particles are recirculating with it unless there is a control to remove them.  

But this is an opinion and worth exactly what you paid for it.   If cases continue as more data becomes available, we will know eventually if it aerosolizes, entrains in droplets or both.  Meanwhile, I will continue to: stay home if I feel ill out of consideration for my coworkers, wash hands frequently, wash commonly touched surfaces frequently and maintain physical distance from strangers when out and about.  Basically, my usual behavior.

Kind Regards,



Alicia Frazier  | 19100 Ridgewood Parkway |San Antonio, TX  78259

-----Original Message-----
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of David Roberts
Sent: Tuesday, June 16, 2020 7:58 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [EXTERNAL] [DCHAS-L] COVID19 spread question

Hello,

OK - I know where this might go, but I'm asking that people give nice, honest answers here and don't judge or rant.  I honestly need somebody to tell me why we all are saying that we need to worry about aerosol transmission when it comes to Covid-19.  My friend worked at the CDC, and is quite knowledgeable on the subject.  She was in Africa during the first Ebola crisis, and knows a bit about transmission and such. She feels that it's truly just a droplet transmission thing (big difference - one can be mitigated by social distancing, the other needs to deal with room ventilation considerations).  

I need evidence stating that somebody has done the experiment on room air to show that the virus is in the air for 3 hours, and it increases over time if you have somebody infected sitting and breathing in the room.  Does anybody have a paper on this that isn't one of assumption and conjecture but has actual data with measurements.

Are we all saying aerosol when we mean droplets?  The CDC website only says droplets - there is no indication that aerosol transmission is a viable way for this virus to transmit, according to the CDC.  

My friend has a theory that if it was truly an aerosol transmission that we would see way more cases.  Doesn't think the virus can live in an aerosol - thinks it may dry up and become non-viable.

I see two different things when I read online about what you need to worry about.  One is saying it's aerosolized and lives 3 hours in air - that's what she is questioning.  Why do we say this?  Is that from a 1950s reference or is there real evidence here for this situation???  The other is droplet transmission, which I feel is a true threat and worry with this virus.  Droplet transmission can be easily mitigated by social distance, hygiene, and mask wearing.  Droplets have some mass and thus don't really float around in the air so much.  Aerosol is much more difficult and scary.

Thanks.

Dave

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