Homeless do get more sunlight than anyone. They are also exposed to greater temp extremes. Also, coastal areas have greater humidity. About the only physical difference I can see. All those would tend to lower their viral density exposure. Their immune systems are probably more exposed to disease also. Now any have lung tissue damage ? Did they check for weakened immune system markers ?
The homeless live like humans lived for centuries- hunting and gathering.
They are very much the ‘honest’ human today.
They live the life our bodies were made for.
The rest of us are spoiled, decadent even. (That’s a good thing- don’t get me wrong!)