It is difficult to detect the intestinal protozoal infections among the HIV-infected persons or travelers diarrhea by using the traditional microscopy or staining methods. The purpose of this study aimed at finding out the appropriate diagnostic methods and the infection rate of the intestinal protozoa, including the Entamoeba, Cryptosporidium and Giardia among the HIV-infected persons by using the antigen detection method and biological method. The investigators also tried to analyze the associated HIV infection status and sexual transmitted diseases (STD) including Gonorrhea, Chlamydial trachomatis, Syphilis, Genital warts and Herpes simplex virus in this study. The study will collect the blood, urine and stool samples from 200 intravenous drug user (IDU) with HIV-infected in the prisons, 400 intravenous drug user (IDU) without HIV infected and 100 intravenous drug user (IDU) with HIV infected receiving methadone maintenance treatment.