All bone graft materials are sourced for certified and licensed bone banks. The graft materials are usually irradiated and the chances of transmission of disease is almost nil. Infection is possible as with any implantation of foreign material. There are other synthetic materials that can be...
Since the tooth was removed due to an abcess the graft most likely failed. The best thing to do is to treat the possible drysocket and infection. Once your tissue has healed the doctor should re-enter the site and place a new graft.
Attend this as soon as posible, its a very delicate area, where the sinus could be involved,and this might be causing problems also on that area, and that could be why it does not heal.