Avian pox on caught blackbird.

Hi, I had been feeding fledgling blackbirds when I noticed one had avian pox. After a while it disappeared but the others seemed to be OK. Yesterday I found the bird in the road. It's beak lesions had gone down a bit but it does have some by its eye now as well. It couldn't fly but its wings seem OK. I kept in in the quite overnight to let it rest and it survived the night. But PLEASE what do I do now.??