Mark Wainberg, Bluma Brenner and colleagues at U de M presented new findings at an AIDS symposium in Montreal on Friday to add to a recently published eight-year study on transmission rates, published in April's Journal of Molecular Biology. Their study, out last month, showed that half of all HIV transmissions happen when newly infected people don't know they are carrying the virus. The new data, from 2,500 HIV patients in several Montreal clinics, dealt with transmission of drug-resistant HIV strains.