by SoCalJim » Tue Apr 07, 2020 8:54 pm
I'm a retired RN, almost 30 years pediatric ICU and emergency, so quite familiar with isolation standards. I believe the "6 foot rule" derives from very old studies to determine how far it is likely that a respiratory (airborne, droplet) microbe (usually virus or bacteria) would be infectious indoors. Those studies would have been based upon upper respiratory infections (common cold, which includes a few less serious coronaviruses), influenza, pertussis, etc. that have been known for decades, at least. The six foot rule becomes anyone's guess outdoors because it would then involve many more factors, not least of which is how strongly is the wind blowing and in which direction. Part of what determines the risk of infection is the concentration of virus in a given space. If a symptomatic person who is presumptively positive with COVID-19 coughs or sneezes in my face (as happened to me many times with kids in the ED, tho not with the current pandemic), I'd be very concerned. If I'm outdoors walking in the near vicinity of other people, I have a very low level of concern because even an asymptomatic infected person is probably emitting a certain amount of virus with each breath, but it's not concentrated or aimed at my face. One way to think about airborne transmission is to picture how smoke behaves when it's exhaled outdoors. It's not a completely accurate comparison since a lungful of smoke tends to be exhaled with some force as opposed to regular breathing, but it gives you an idea. What I'm getting at is that even a sick person's exhaled virus would dissipate in the air fairly quickly so that the chance of someone inhaling a big breath full of virus outdoors is pretty damn low. Another way to look at it: we all know that people, kids and adults, pee in pools and the ocean, but it becomes diluted pretty fast. That knowledge doesn't keep most people out of the water. And yeah, pee in a swimming pool isn't the same health risk as coronavirus.
BTW, went grocery shopping for the first time in about 10 days. I'd estimate that about 90% of people were wearing a face covering in the stores. I had originally thought that the recommendation/mandate to wear a mask in stores was overkill, but when I heard some experts say that it may help block some virus exhaled by infected people (asymptomatic or not) and might help slightly to prevent inhaling virus, I thought, okay, that sounds reasonable. Almost everyone not wearing a face covering today was well under 50. To anyone not following the current CDC recommendation to do so, you're either uninformed, selfish, or naive in believing you won't get sick.