My first FIV cat was used to being outside but only ever went into the garden when I went with her so when I found she was positive I didn't change that. The positive cats I've had since pussy willow have all been indoors, with access to an enclosed run (which has grown over the years) so they're still safe but can get fresh air. I'll always have FIV cats so the situation will always be the same here, and to be honest I don't think my nerves would take it if I had cats that I let out free to roam, I know I would worry too much!