All you can do it state it categorically on your profile, and if anyone asks when contacting you, you block them. And if they ask at the booking you kick them out. And if they try it, you call the police.
It's the only way.
I've had clients tell me that it's OK because they're clean, and recently (about ten days ago) I had a client tell me that it shouldn't matter if I'm clean and on the pill, plus because I already have kids so it shouldn't matter. No idea what he meant by that.