Relative Risk of Various Activities?

[Mdcastle]

I know there’s a lot we don’t know, but on a scale of 1-10, where one is never leaving your basement or contacting another human with fresh air drawn in through a HEPA filter, and 10 being inhaling deeply while being coughed on repeatedly by someone who’s tested positive, is there any way to quantify the risk of everyday activities. I’ve seen claims that most of what we’re doing is basically security theater, and most transmission is places where viral load is high like a hospital full of sick patients or lingering close together in a small enclosed place for a period of time.

Going to a grocery store or Home Depot where you might pass someone in the aisle but are careful not to linger too close to them.

Bicycling or jogging while passing someone on an 8 foot path

Picking up take-out food and eating the food

Going through a fast-food drive through and eating the food

Touching an ATM keypad or gas pump handle and not being able to wash your hands right away.

Picking up the days mail

[needscoffee]

@Mdcastle

I’ve seen claims that most of what we’re doing is basically security theater, and most transmission is places where viral load is high like a hospital full of sick patients or lingering close together in a small enclosed place for a period of time.

Going to a grocery store or Home Depot where you might pass someone in the aisle but are careful not to linger too close to them.

I suspect NYC would disagree with you on that. While subway cars and buses are likely higher viral load than walking on an open street, if we’re just making up guesses here, I’d guess that stores offer lots of opportunity to breathe in other people’s shed aerosolized viruses from the air, even if the one shedding has already walked past briskly.

[needscoffee]

@needscoffee

I suspect NYC would disagree with you on that. While subway cars and buses are likely higher viral load than walking on an open street, if we’re just making up guesses here, I’d guess that stores offer lots of opportunity to breathe in other people’s shed aerosolized viruses from the air, even if the one shedding has already walked past briskly.

Plus the risk to the cashiers and clerks is a lot higher than to a person shopping for 15 minutes. They’re breathing in the virus their entire shift, and they’re coming down with it.

[Horatius]

@Mdcastle

I’ve seen claims that most of what we’re doing is basically security theater, and most transmission is places where viral load is high like a hospital full of sick patients or lingering close together in a small enclosed place for a period of time.

I haven’t seen the numbers on this, but let’s assume for now that this is true.

Well, really, that’s to be expected now, because we’re doing the whole social distancing thing, aren’t we? The whole point of that is to lower the risk of infection during everyday activities, so of course, now, most new infections might be coming from places like hospitals, where sick people tend to congregate.
But ask yourself this - where were people picking up this disease in January and February? It’s unlikely that most of those people just happened to be in a hospital or “small enclosed space” with one of the people who brought this back from their vacations or business trips. It most likely spread during regular everyday activities.

[Fretful_Porpentine]

I, too, would like to know more about this, but this article seems to suggest transmission occurs most often in the home or on transit, and nearly always in indoor venues. (Granted, it’s based on data from China in January / February, so I don’t know that people would have been spending a lot of time outdoors.)

[Frankenstein_Monster]

My answer to the OP:

Science says you get the virus from other people. So not meeting other people has a relative risk of 1, on your scale. Any involvement with other people would have a relative risk higher than 1.

“Picking up the mail” would be 1. Fast food drive-in might be 1 or 2. I think ATM keypad etc is not exactly proven to be worse than 1, but it might be.

All the other ones are low risk but involve meeting other people. I’d call them 2. It really depends on whether those other people are infected.
I have had a similar relative risk question / thought experiment as the OP. If I may piggyback on the thread:

Imagine people on a packed bus. Every seat taken, a few people standing.

One person sits at the back of the bus and has the virus. No one else does. The infected person sneezes ONCE.

Over the next 15 minutes the people gradually get off at the following stops.

How many people will be infected?

I think 2 or 3. Except if the infected person is talking much of the time. Then it would be the people they were talking to, plus those 2 or 3. Say, 7 or 8.

In particular I don’t think the answer is, “all the other passengers”, not even close. Otherwise my whole country would already have been wiped out 10 times over.

I have some data:

COVID-19 Outbreak Associated with Air Conditioning in Restaurant, in particular, see the figure.

Nine people infected, and that was a worse scenario than my bus. The exposure was for an hour, and presumably, the person was talking all the time.

Am I too optimistic?

[DSeid]

On the one hand, the typical close household contact circumstance results in infection from under 15% to under 5% of the time depending on the study, mostly towards the low end. So for most brief passes within a few feet in grocery stores and the like the risk is likely very very very tiny.

The rub is that not all with COVID-19 are typical. Some may be minimally contagious and a few may be “super spreaders.” The harms one unwitting super spreader could cause with a few casual interactions in crowds is immense, in particular if the super spreader coughs or shouts without a mask on and/or otherwise adequately covering their mouth.

Still we can use super spreader events (SSE) as the high end for risk.

… With few exceptions, almost all of the SSEs took place indoors, where people tend to pack closer together in social situations, and where ventilation is poorer. (It is notable, for instance, that the notorious outbreak at an Austrian ski resort is connected to a bartender and not, say, a lift operator.) … Of the 54 SSEs for which underlying activities could be identified, only 11 did not involve either religious activity, a party, a funeral, a cruise or extended face-to-face professional networking. But even in this minority of cases, one can observe almost identical interpersonal dynamics. Three of the SSEs—in Japan, Skagit County, WA, and Singapore—involved concert-goers and singing groups belting out tunes together over a period of hours. (The Skagit example is particularly interesting, because the organizers were aware of the COVID-19 risk beforehand, and took the precaution of spacing out the participants by several feet. If they had been merely chatting, instead of singing, no one might have gotten sick.) …

So let’s look at one infamous super spreader, the South Korean women and the Shincheonji Church of Jesus.

According to Reuters, “The Korea Centers for Disease Control & Prevention (KCDC) said on Saturday they had obtained a list of 9,300 people who had attended those two Shincheonji church services, around 1,200 of whom had complained of flu-like symptoms. Hundreds of cases have now been confirmed there.”

The cases in South Korea subsequently grew exponentially and hundreds of cases could be linked to Patient 31. Authorities called her the “super spreader”.

Super spreader individual in an SSE environment, risk to any specific individual was somewhere below 13%.

That at least places a limit on it.

Still if every small contact is a grain of sand worth of risk enough of them can still bury us. The issue is not how high those sorts of risks are but how many of them there are in many of our usual lives’ days.

And again that one of those infected with SARS-CoV-2 people is much more contagious than all the others and happens to yell, cough, or sneeze in your direction uncovered at just the right time.

[RioRico]

My guesstimates:

@Mdcastle

Going to a grocery store or Home Depot where you might pass someone in the aisle but are careful not to linger too close to them. risky

Bicycling or jogging while passing someone on an 8 foot path minimal risk

Picking up take-out food and eating the food unknown risk

Going through a fast-food drive through and eating the food unknown risk

Touching an ATM keypad or gas pump handle and not being able to wash your hands right away. risky

Picking up the days mail it depends

Re: takeout food - Our local pizza parlor is a phone-order take-n-bake. We can disinfect the wrappings and I doubt the virus will survive our oven. Any other takeout option seems risky for us old farts.

Re: mail pickup - I empty our PO box once or twice a week now when nobody else is in that area. I’m gloved; mail goes into a plastic bag. At home, I sanitize, and the bag is quarantined a few days before opening. I hope the risk is low.

[DSeid]

FWIW on my way home from work I heard Dr. Ashish Jha, of Havard, being interviewed on the Sirius channel POTUS by Oliver Knox (“The Big Picture”) discussing this very question. His answer was that he thinks the casual contacts (like those in the op) are a very very tiny albeit non-zero risk, and fomite transmission likely less. Mostly more prolonged contacts. His argument to back that perspective up was based on contact tracing - contact tracing can almost always find the chains of transmission, if those casual contacts were at all significant links in the chain then they’d be untraceable, and the chain would not be able to be followed as consistently as has been able to be followed to date.

It seems a good argument.

[Corry_El]

@needscoffee

I suspect NYC would disagree with you on that. While subway cars and buses are likely higher viral load than walking on an open street, if we’re just making up guesses here, I’d guess that stores offer lots of opportunity to breathe in other people’s shed aerosolized viruses from the air, even if the one shedding has already walked past briskly.

It is guessing if the argument is in absolute terms ‘there’s no risk to this’ etc. Unfortunately AFAIK there is no solid public evidence that really quantifies the risk of various situations in NY either (I live in Hudson Cty NJ across the river and it’s similarly densely populated and also a COVID hotspot).

Anecdotal sampling of expert opinion seems to be next to zero risk in outdoor situations following the original basic guidelines, 6’ and hand washing. I’ve see added ‘<6’ for less than 6 seconds’. Various epidemiologists have expressed frustration of what they view as ‘aerodynamics not epidemiology’ in ad hoc studies/simulations on the internet. IOW the guess that somebody briefly passing you even indoors in a store is any real risk is a guess that could easily be wrong. However we’ve largely avoided stores, younger grown kids do most of our grocery shopping.

In workplaces, besides commuting by mass transit, you spend much more time with people who could be infected. And 6’ isn’t practical in elevators even where people commute to work by car. Also the virus is in infected people’s stool and flushing a toilet creates a cloud of it. Various aspects of office work could be way more risk that shopping carefully, let alone walking around outside.

Relatively, but the problem remains lack of any public data I know of to put absolute numbers on any of these things. It doesn’t ‘stand to reason’ that the risk is non-negligible in various common settings just because new cases continue to arise, not dropping so fast even in various ‘locked down places’. But we don’t know (I don’t anyway) what % of those are in household settings or the people I see just when walking around, again in a hot spot area, who aren’t taking the basic precautions.

But if guessing, my guess is all OP’s situations are very low risk assuming the basic precautions.