Today’s Topic: What Do We Know About Exactly How Coronavirus is Transmitted?


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Today’s insights are slightly longer, so bear with me. (Number 5 will be shorter, trust me). About a dozen critical studies were published in the last week that address the question: “How exactly is this coronavirus transmitted?”--the answer to which is the first step in understanding (1) which aspects of social distancing are critical?, and (2) how can we protect health care workers?


Because this feels important, I am going to start with the summary of what we now understand about coronavirus transmission:


1.        Coronavirus is spread primarily by coughing--an infected person, whether they have mild symptoms or severe Covid19 illness, coughs frequently, and with each cough “sheds” virus in aerosol droplets, which extend a few feet into the air.


1a.        It’s not just coughing, though--breathing while sick is almost certainly enough to shed virus.


2.        Those droplets can remain in the air for approximately a few hours. These aerosolized droplets do not appear to be the major route for the average person to contract this coronavirus, however. In other words, yes, if you just sit statue-like with folded hands in a closed space where an infected patient recently has been coughing--or breathing--you can absolutely inhale the virus and contract the infection. So, this is something we need to intervene against; ergo, strict social distancing, no meetings in closed spaces, and work from home. What I am saying is that the data suggest this is not the main mechanism driving community spread of this pandemic.


2a.         Aerosols are, however, a major risk for health care workers, and likely a significant route by which health workers are contracting coronavirus. They spend a lot of time in enclosed spaces with patients expelling aerosols. This emphasizes how critical is personal protective equipment (PPE)--especially masks--for health workers, and why ongoing shortages in hospitals are so distressing.


3.        OK, so what is the main mechanism of community spread? The expelled droplets quickly settle on surfaces. Once there, in the absence of any effort to clean, coronavirus can remain viable and infectious on surfaces for several days. It depends on the surface: for some surfaces, coronavirus remains infectious for up to 9 days; on most surfaces--plastic, stainless steel-- without cleaning, it will degrade in 2-3 days. 


4.        This factor--contaminated surfaces--does appear to be the major route of community transmission of coronavirus--meaning, you touch a table, a doorknob, a keyboard, or really any public surface accessible to an infected patient’s nearby fits of coughing. And then you touch your mouth/nose/face. This is why--and I cannot emphasize this enough--hundreds of public health experts have been shouting from the rooftops to (1) clean surfaces frequently, (2) wash your hands, and (3) stop touching your face.


5.        The good news here is: (1) knowing this information is really helpful if you want to minimize your own risk; (2) the virus itself is really easy to sanitize--soap and water, hand sanitizers, bleach wipes--basically, anything you use to clean surfaces and clean your hands will sanitize those surfaces and effectively eliminate transmission--reduce R0; and (3) even in households where one person is unknowingly infected, most people can remain uninfected by practicing thoughtful and rigorous handwashing, hygiene, and physical distancing.

What’s hard is this: we all have to unlearn a lifetime of behaviors covering where we put our hands, and how often we wipe down surfaces. And unlearn it fast.

In essence, you’ve just read today’s entire Insight. What follows are the data, and some detail, as well as some thoughts on school closings and some global updates. 

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Copyright - Greg Van Kirk 2020