What constitutes a safe distance when it comes to the spread of COVID-19?
The answerdepends on where you live.
The truth is, we dont yet know how far is far enough when it comes to coronavirus.
A recent study found the virus in air as far asfour meters away from infected patientsin a COVID-19 ward.
Why such a range of safe distances?
Thats because social distancing is a complex problem with many variable influencing factors.
Here are four of the most important ones.
The larger droplets, which carry more virus particles, settle more quickly due to gravity.
The smaller droplets, carrying fewer particles, can remain suspended in the air for hours.
40% off TNW Conference!
A cough produces more droplets overall and a greater proportion of them are larger.
Breathing produces fewer droplets overall and they are generally smaller.
We also know that people without symptoms can shed the virus.
The infectious dose for influenza strains varies fromthousands to millionsof copies.
We do not yet know this number for SARS-CoV-2.
In any case, we can be certain that the infectious dose will vary between different people.
A lot depends on our environment when it comes to how water droplets spread.
TravelerPix/Shutterstock
Air currents will blow droplets around in various directions.
Good ventilation will dilute the number of droplets in the air.
Temperature and humidity will affect the rate at which water evaporates from droplets.
All this will affect our understanding of how much distance to keep in different types of space.
Lets start with this scenario: three people are in a room that is not ventilated.
One of them is infected and two are not.
The infected person coughs, producing a cloud of droplets.
The larger droplets carrying more virus particles settle more quickly due to gravity.
The smaller droplets carrying less virus travel further.
Of course, the above scenario is overly simple.
An open window may blow air in a particular direction.
The infected person may cough repeatedly during a period of time.
An air conditioner might recirculate air around a room.
Room temperature and humidity may result in drying leading to smaller particles carrying higher concentrations of virus.
There is an infinite number of scenarios and having one rule that applies to them all is impossible.
They cannot apply in all contexts.
This article is republished fromThe ConversationbyLena Ciric, Associate Professor in Environmental Engineering,UCLunder a Creative Commons license.
