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Airbrush

Coronavirus and the Great Outdoors

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Here is my Coronavirus question for anyone.  If I am jogging around my neighborhood in the morning, and somebody with Coronavirus sneezed or coughed at the sidewalk in front of their house, just before I pass by the very spot, how long is the virus dangerous to me?

Even if the wind speed is almost zero, the droplets will drift, dilute, and disburse, but it could drift in the wrong direction for someone passing by.  Don't the droplets evaporate leaving the virus high and dry?  Then does the sunlight not kill the high and dry virus?  How long does it take sunlight to kill the airborne virus after a cough or sneeze?

 

Edited by Airbrush

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I think there is no clear answer to that. Studies basically are looking it from two perspectives. One mechanistically, which looks at virus survival in droplets and ejection and the other is epidemiological where folks look at likelihood at being infected outside. From the latter viewpoint, it appears that casual outdoor infections are very rare and mostly connected with folks being close to each other. 

Mechanistically, evidence suggests that e.g. in saliva it would take minutes for sun-inactivation of SARS-CoV-2 (~6 minutes for 90% inactivation), so at least theoretically if someone sneezes in the air and you run straight through it, you might get exposed to active particles (sneezing on the ground would arguably be safer). But again, most evidence suggests that overall infection chances are low under these conditions.

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On 9/17/2020 at 9:48 AM, CharonY said:

I think there is no clear answer to that. Studies basically are looking it from two perspectives. One mechanistically, which looks at virus survival in droplets and ejection and the other is epidemiological where folks look at likelihood at being infected outside. From the latter viewpoint, it appears that casual outdoor infections are very rare and mostly connected with folks being close to each other. 

Mechanistically, evidence suggests that e.g. in saliva it would take minutes for sun-inactivation of SARS-CoV-2 (~6 minutes for 90% inactivation), so at least theoretically if someone sneezes in the air and you run straight through it, you might get exposed to active particles (sneezing on the ground would arguably be safer). But again, most evidence suggests that overall infection chances are low under these conditions.

Thanks for the info.  Suppose someone sneezes or coughs and droplets of various sizes are ejected.  These droplets float in the air, the heaviest ones drop to the ground.  All the other droplets evaporate in minutes.  That means the droplets all shrink in size until they completely evaporate and the virus is left dry and light as smoke.  Then, as you said, sunlight kills the dry virus in minutes.  That is why outdoor infections are low?

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!

Moderator Note

Moved out of the Lounge because this is not a “Lounge” topic

 

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13 hours ago, Airbrush said:

Thanks for the info.  Suppose someone sneezes or coughs and droplets of various sizes are ejected.  These droplets float in the air, the heaviest ones drop to the ground.  All the other droplets evaporate in minutes.  That means the droplets all shrink in size until they completely evaporate and the virus is left dry and light as smoke.  Then, as you said, sunlight kills the dry virus in minutes.  That is why outdoor infections are low?

Basically yes. In addition, outdoors whatever lingers in the air dissipates over a larger volume so unless you just breathe in the droplet shortly after ejection, your exposure is fairly low.

There is some disagreement about the infectivity of small aerosols. There is data suggesting that Sars-CoV-2 may still be infectious in these tiny droplets, but it is not quite clear as the rate of infections seems lower than other diseases that are transmitted via these aerosols. It should probably be added that the distinction between droplets and aerosols (and airborne) is also slightly a artificial distinction, though in practice they call for different countermeasures. 

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