1/17 Thread - My Take
My take based on a lot of reading, data analysis, modeling, and discussions with many bright & long-time colleagues from around the world (CIA - Clan of Indoor Air).
My take based on a lot of reading, data analysis, modeling, and discussions with many bright & long-time colleagues from around the world (CIA - Clan of Indoor Air).
2/17
The debate over whether the airborne transmission route occurs is over. Many of us have claimed its relevance from very early in this pandemic. It was real then. It is real now. Period. We all benefit if we acknowledge this & act accordingly.
The debate over whether the airborne transmission route occurs is over. Many of us have claimed its relevance from very early in this pandemic. It was real then. It is real now. Period. We all benefit if we acknowledge this & act accordingly.
3/17
But does this mean that the airborne route is always the dominant or only transmission route? No.
It is definitely a relevant transmission route & may, in some situations, be the most important route. As such, we should prevent it just as we do close contact & fomites.
But does this mean that the airborne route is always the dominant or only transmission route? No.
It is definitely a relevant transmission route & may, in some situations, be the most important route. As such, we should prevent it just as we do close contact & fomites.
4/17
Is transmission by close contact important? Yes.
Is transmission by fomites important? Probably.
Does one transmission pathway always dominate?
Probably not. In fact, every scenario will likely be different in terms of its “attribution pie chart”.
Is transmission by close contact important? Yes.
Is transmission by fomites important? Probably.
Does one transmission pathway always dominate?
Probably not. In fact, every scenario will likely be different in terms of its “attribution pie chart”.
5/17
For example, close contact and the airborne (what I call far field) pathways will not be relevant if no infectors are present, but the fomite pathway might be (think of someone cleaning a busy bar after closing time or a custodian cleaning a classroom at night).
For example, close contact and the airborne (what I call far field) pathways will not be relevant if no infectors are present, but the fomite pathway might be (think of someone cleaning a busy bar after closing time or a custodian cleaning a classroom at night).
6/17
We should all know by now that densely packed indoor environments w/ poor ventilation & where people spend a lot of time magnify EACH transmission (infection) pathway. If you can avoid these environments, do so. If you work in one, reduction of all pathways should matter!
We should all know by now that densely packed indoor environments w/ poor ventilation & where people spend a lot of time magnify EACH transmission (infection) pathway. If you can avoid these environments, do so. If you work in one, reduction of all pathways should matter!
7/17
And if the environment includes people speaking loudly to be heard, singing, playing wind instruments, screaming political slogans, etc., emissions from infectors who are present further magnifies exposure and risk.
And if the environment includes people speaking loudly to be heard, singing, playing wind instruments, screaming political slogans, etc., emissions from infectors who are present further magnifies exposure and risk.
8/17
High density increases the probability of having one, or perhaps even many, infectors present, which also magnifies risk. And the more people that are present the higher the probability that one or more susceptible persons will be exposed and become sick.
High density increases the probability of having one, or perhaps even many, infectors present, which also magnifies risk. And the more people that are present the higher the probability that one or more susceptible persons will be exposed and become sick.
9/17
High density and long time periods magnify infection by close contact and also infection by fomites. High density, poor ventilation, and lengthy exposure times also increase airborne transmission.
High density and long time periods magnify infection by close contact and also infection by fomites. High density, poor ventilation, and lengthy exposure times also increase airborne transmission.
10/17
So, why should we argue over which transmission route is most important or dominant?
Attempts should be made to lesson exposure to all infection pathways. Failing to do so makes little sense if our aim is to squash the incidence of COVID-19.
So, why should we argue over which transmission route is most important or dominant?
Attempts should be made to lesson exposure to all infection pathways. Failing to do so makes little sense if our aim is to squash the incidence of COVID-19.
11/17
What can significantly reduce all three pathways in the previous examples?
Masks. Masks. Masks. Simple. Low cost. Smart.
What can significantly reduce all three pathways in the previous examples?
Masks. Masks. Masks. Simple. Low cost. Smart.
12/17
But most do not want to wear masks in bars/restaurants. If these are open this summer/fall it is smart to move outdoors with ample physical distancing, and as much take-out from restaurants as possible.
Aside: Big tips for service workers who are at high risk!
But most do not want to wear masks in bars/restaurants. If these are open this summer/fall it is smart to move outdoors with ample physical distancing, and as much take-out from restaurants as possible.
Aside: Big tips for service workers who are at high risk!
13/17
Wearing masks indoors when others are present should be mandatory if we want to appreciably lower COVID-19 cases and get back to a much better place that helps the economy open safely and for a prolonged period (instead of opening and closing in fits and starts).
Wearing masks indoors when others are present should be mandatory if we want to appreciably lower COVID-19 cases and get back to a much better place that helps the economy open safely and for a prolonged period (instead of opening and closing in fits and starts).
14/17
But while wearing masks (away from home) is critical & significantly reduces risk, it does not make risk zero. Reducing density wherever possible, greater physical distancing, improved ventilation/engineering control should be implemented to further reduce risk.
But while wearing masks (away from home) is critical & significantly reduces risk, it does not make risk zero. Reducing density wherever possible, greater physical distancing, improved ventilation/engineering control should be implemented to further reduce risk.
15/17
Wash your hands and do not touch your face - guidelines that seem like from 10 yrs ago - is still smart. And, of course, quarantine if you have had contact w/ someone infected with COVID-19, call your doctor and isolate at home if you feel COVID-19 symptoms.
Wash your hands and do not touch your face - guidelines that seem like from 10 yrs ago - is still smart. And, of course, quarantine if you have had contact w/ someone infected with COVID-19, call your doctor and isolate at home if you feel COVID-19 symptoms.
16/17
And limiting, putting on pause, or modifying activities that generate the release of a lot of respiratory particles is just smart. Quieter = safer.
And limiting, putting on pause, or modifying activities that generate the release of a lot of respiratory particles is just smart. Quieter = safer.
17/17
Many deadlines in my day job & working (far too slowly) on several papers.
Occasional but much fewer tweets from me for next couple of weeks. My activity for rest of summer will focus on "back to school" modeling/planning.
Stay safe. Be patient. Keep your guard up.
Many deadlines in my day job & working (far too slowly) on several papers.
Occasional but much fewer tweets from me for next couple of weeks. My activity for rest of summer will focus on "back to school" modeling/planning.
Stay safe. Be patient. Keep your guard up.
