I didn't separate my rooster, who never stopped being active with my hens, and never had another hen with fowl pox. But, now after what Hobbits Mama said, I would probably do it differently and separate him. I think I was just lucky.
That is fowl pox. I had a rooster with it once. I know it can spread to the other chickens, but once they are exposed it's too late to separate. At least that's what I was told. So your chicken's case doesn't look too bad. My rooster had about 5 or 6 spots, and although it looked bad for a...