I've seen lots of pen sharing, food serving utensil sharing, outdoor bathroom nob touching, etc over the many years i've gone to great strides events. oh yes and one CF mom will hug the other CF mom....
remember, just because you're outdoors doesn't mean bacteria don't stick on items that everyone touches. just because CFer's dont' touch doesn't mean that these CFer's aren't vulnerable... bacteria can easily be brought home but hugging, hand shaking, and even on your shoes (CFer's cough a LOT and you could easily step in microscopic sputum on the ground).
so i go, but i use my own pen, i wave and smile instead of hug (hard because I have a big instinct to shake hands and/or hug), and i ask someone else to serve me at the food area.
and like after clinic or a hospital stay, shoes stay outside my house for 4-5 days.
happy walking!
<b>Edited to add:</b> PA can survive on surfaces for DAYS, so areas like schools, churches and anywhere else a CFer can be is always an issue. even if you're not at a location for the same time, bacteria can hang out and infect another CFer long after you leave....