The problem is chicken pox is contagious before you see the spots, so even though your husband hasn't had much contact since the outbreak he could still have caught chicken pox.
Has your husband already had chicken pox? If he has he shouldn't have too much to worry about, but if he has never had it it is vital that you letter his doctor know due to him being on steroids.
My 16 yr old has a very low immune system so I have to be very careful who he is around, and he has often been on steroids, and this lowers the immune system even more. Certain illness's can make him become very ill to the point he ends up i hospital, so your husband needs to be very careful while on prednisolone. Contact your GP to see what they say.