So sorry you had to let them go but hopefully they found a wonderful new home. Since the day I got chickens I've been so paranoid about biosecurity. Reading stories like yours make me even more so. I've already decided I won't add started pullets to my flock, only chicks that are brooded in the garage. I want to go to the state fair to see the poultry this weekend but am afraid of bringing something home on my shoes etc. I am afraid to have visitors that have chickens over to my house or to go to theirs. Between mycoplasma, marek's and all the other scary flock killing things it's almost like I want to put my chickens in big hamster balls.
You can go to the fair. I have been many times. Make sure when you get home, you wash up and change your clothes and shoes. You should always wear/have "chicken" shoes. I have my crocs that I wear only in my backyard. This also goes when you go to the feed store.
As for your chicken friends, require the same. On the Tour de Coops, you must step on a mat with disinfectant before going into see the coops. This year they have 30 coops to visit.
When I visit my chicken friends, I wear their "chicken" shoes. do not wear your "chicken" clothes when going to their house. Just make sure you always wash your hands.