Herd immunity regarding Covid 19 is around 70%. The measles was around 95% but that had a R of 15 (one person infected 15 others). So measles was about 5-7 times more infectious.
A respected biologist had this reply to a comment on hiking (whether hiking behind someone else into the wind is risky).
Hiking. 3 hours of drafting someone could potentially lead to infection. But, I tend to think that the outdoor environment rapidly dilutes infectious material and the risk would be low.
But there are many caveats. Some people release huge amounts of infectious material, others very little (that is assuming they are infected). Same with infectious dose, it’s different for different people.
Of course, this was not wearing a face covering. If you're uncomfortable drafting someone then pull up a bandana that's hanging around your neck until the wind blows differently or you take point.
