High HIV incidence among persons who inject drugs in Pakistan: greater risk with needle sharing and injecting frequently among the homeless. oleh Rab Nawaz Samo, Arshad Altaf, Ajmal Agha, Omrana Pasha, Shafquat Rozi, Ashraf Memon, Saleem Azam, Meridith Blevins, Sten H Vermund, Sharaf Ali Shah