What is the COVID exposure risk from passing close by someone who is jogging relative to passing close by someone who is walking?

The reason I ask is with regard to going out for exercise, or to run errands: going out early in the morning means passing fewer people, but a larger percentage will be joggers. I'm trying to figure out whether there is an overall risk reduction, whether early morning is safer than the middle of the day.

I have only been able to find answers to adjacent questions:

'Either way, the risk is low outdoors versus indoors.'

Right. But what's the relative risk between these two low-risk outdoor events?

'Ideally, you should keep 4.5m separation from joggers.'

Ideally yes, but as it turns out, sidewalks are not 4.5m wide.

'We don't have enough data to be sure.'

Right. But decisions have to be made based on the best currently available guess. What's the best currently available guess for this? 1.1x? 2x? 5x? 20x?

  • 1
    Not an unreasonable question, but like some other environmental questions about the spread of Covid-19 it's probably not answerable except with simulations, which may or may not be close enough to reality, due to lack of calibration on actual outcomes. Oct 16, 2021 at 6:25
  • 1
    And your Q is probably still non-answerable even if you substitute Covid-19 with a pathogen that has been studied for much longer, be it some influenza, common cold etc. Oct 16, 2021 at 6:33
  • I think the only best guess available is "as far as possible." Have you considered things like wind? A still day and a breezy day would almost certainly yield significantly different results. Probably the same with rain, snow, extremes of temperature, etc.
    – Carey Gregory
    Oct 17, 2021 at 5:24
  • @Fizz The problem is that 'non-answerable' only exists as a concept when you're writing for a scientific journal. When you're making a decision in real life, you necessarily end up answering the 'non-answerable' question anyway. You have to pick a time of day to go out; you can't go out at an unspecified time. If you decide by coin flip, you're still answering the question, just in a random way. And I do not believe that domain experts could not guess at least somewhat more accurately than a coin flip.
    – rwallace
    Oct 17, 2021 at 7:55


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