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Covid-19 infections are starting to overwhelm hospitals. We have patients waiting in our ED hoping to get ICU beds, we have refrigerator trucks outside hospitals. We need every medical professional and member of the community to work together to help reduce viral transmission.
I've worked in overwhelmed hospitals and I know how challenging it is. Now, as a primary care doctor, I hope that I can explain the science of how the disease spreads so that we can all prevent future infections and make 2021 a better year.
One thing that has been confusing is that COVID-19 can spread into the air when an infected person breaths, talks, sings, ect. A visual analogy is smoking. Like smoke, covid-19 is most concentrated close to the infected person. Overtime the smoke can fill a room with a haze.
Unlike smoke, Covid-19 cannot be seen. It is often spread by people before they show symptoms. There is no way to know that someone is spreading the disease. But we can take steps to protect others and ourselves.
None of the steps by themselves can prevent disease 100%. So we combine protections to reduce the chances of getting infection. Most of these things are not difficult to do as long as we all understand why we are doing them.
Some things that increase how much virus one is exposed to are:
1. How close someone is to an infected person
2. How much virus the infected person is sheading
3. How much fresh air is coming into the space to clear out the virus
4. Duration of time of exposure to virus.
1. How close someone is to an infected person
2. How much virus the infected person is sheading
3. How much fresh air is coming into the space to clear out the virus
4. Duration of time of exposure to virus.
#Covidriskchart from @trishgreenhalgh is a good graphic to help understand levels of risk. @ShellyMBoulder has some great data on risk reduction when it comes to music. Simplistically, the more air one breaths in from an infected person, the higher the risk of getting infected.
How do you reduce risk?
1. Distance. 6ft is not a distance at which virus disappears from the air and it is safe. Social distancing helps because there is more virus closer to an infected person and less as one gets further away.
1. Distance. 6ft is not a distance at which virus disappears from the air and it is safe. Social distancing helps because there is more virus closer to an infected person and less as one gets further away.
Indoor spaces can trap virus, like smoke causing a haze in room, and then there is no safe distance because the virus has spread throughout the room. So distancing helps but it isn't enough to prevent infection, especially when inside.
2. Amount of viral spreading? It varies. Generally, it is highest just before symptoms & at the start of symptoms. Masks reduce amount of virus that is shared. Masks do not block 100% of the viruses. The tighter the mask fits, the more it helps. https://science.sciencemag.org/content/368/6498/1422
Masks worn under the nose are not as effective. It is important to wear a mask that covers the mask and nose for the mask to work. Face-shields alone do not stop small viruses in exhaled breath from getting into the air.
Distancing helps but there are examples, especially super-spreader events, showing there is not a safe distance inside. Masks help but they do not block 100% of viruses. We really need to get this virus under control. What else can we do to prevent infection?
We can control how much clean/fresh air is coming into a space to reduce the amount of virus in the air. How can I tell how much clean air there is? We can use a CO2 monitor. When we breath out, we exhale CO2. If exhaled breath is accumulating in a room the CO2 level will rise.
The CO2 level estimates of how much air in the room is shared. Outside CO2 is about 410. Inside CO2 levels of 500 are excellent. Inside CO2 levels of 800+ mean air is being shared. If there is an infected person in the room, this increases the risk of spreading disease.
If more fresh air is brought in the CO2 level will drop. There are places where CO2 levels are posted in indoor spaces so that people their can see the space is getting a good amount of fresh air. I would love to walk into a building and see a CO2 reading of 5-600!
CO2 monitors are $100-150 and it is possible for people to measure these levels themselves. There are places like #CovidCO2 where people can share their readings here on twitter. More info on CO2 monitors: https://docs.google.com/document/d/1K6gqMH4UXl6ljObtWooTJSyFskCkQFx3CXFtkNGBsDs/edit
Many homes are poorly ventilated which makes them prime places for living room spread and household transmission. This why seeing friends outside, distanced, with a mask is helps reduce disease spread! @ShellyMBoulder has a guide: https://shellym80304.com/2020/11/02/most-homes-are-poorly-ventilated-what-does-this-mean-for-covid-19/
A negative test does not mean that it is safe to see people inside without a mask. These tests are wrong too often. Covid-19 infection continues to spread when people thought they were safe. Please don't use a negative test to know that someone cannot spread disease!
If the CO2 reading is, then what? Then think about ventilation (bringing outside air) and filtration (cleaning air). The easiest things to do is let in fresh air by opening doors and window. Mechanical ventilation (HVAC) systems can be adjusted to increase outside air.
There are ways to clean the air. Hepa filters are often portable ways to clean air. MERV 13 filters can be strapped to box fans to create portable filters. Some HVAC systems can use MERV13 filters or higher to remove virus.
On Twitter, there is a lot more information about this from the experts such as @ShellyMBoulder @jljcolorado @CorsIAQ @DavidElfstrom! Two guides that I found helpful are …https://aiha-assets.sfo2.digitaloceanspaces.com/AIHA/resources/Guidance-Documents/Reducing-the-Risk-of-COVID-19-using-Engineering-Controls-Guidance-Document.pdf and https://docs.google.com/document/d/1fB5pysccOHvxphpTmCG_TGdytavMmc1cUumn8m0pwzo/edit#
There is a great guide for schools and teachers that could be applied to home pods or other places @j_g_allen https://schools.forhealth.org/ventilation-guide/
A lot of teachers have found some of these you tube videos helpful. There is more info from @CorsIAQ @JimRosenthal4
Making a Box Fan Filter:
Box fan + MERV 13 filter:
Making a Box Fan Filter:
Box fan + MERV 13 filter:
One other factor that we can use to reduce infection is time. Reducing the time of contact with others reduces the chance of infection. Implementing strategies into business and social interactions to reduce the time of contact between people will reduce infection.
We can use these strategies to stop the burden of disease.
1. Distance: there is no "safe distance", especially inside, so combine with other strategies.
2. Masks: reduce the amount of virus we share. The tighter the fit over the nose and mouth the better.
1. Distance: there is no "safe distance", especially inside, so combine with other strategies.
2. Masks: reduce the amount of virus we share. The tighter the fit over the nose and mouth the better.
Face-shields alone & plexiglass alone are not sufficient barriers to prevent disease spread.
3. Be aware of shared air: Outside with masks & distance when possible. Look for or make indoor spaces with good ventilation & filtration. Co2 monitoring is a tool (with some limitations). Avoid contact with others without masks and poor ventilation settings (homes?)
4. Limit the duration of contact. Businesses can use work from home strategies, stagger shifts, reduce building occupancy, move outside. We can keep social interactions brief. None of these tools alone will prevent disease spread. We need to use these together!
This threat is meant to be an intro and not comprehensive. There are a lot of great experts mentioned in this thread (and more @kprather88 @linseymarr @Don_Milton!) who explain a lot more of the details. Please follow them for more info. I wish everyone health & happiness 2021!
