Angela A. Aidala, Ph.D., is an associate research scientist at the Joseph L. Mailman School of Public Health at Columbia University in the Department of Sociomedical Sciences. Her primary interest is the intersection of economic, social, and cultural influences on health and illness among disadvantaged populations. Dr. Aidala’s work focuses on research, teaching, and service delivery strategies to work effectively with harder–to–reach or “hidden” populations in urban settings, including the homeless, mentally ill, substance users, HIV–infected adults, and youth. Dr. Aidala has directed more than 20 collaborative community health or services research projects. Her recent work is studying housing/lack of housing and HIV prevention and care and methodological and statistical approaches to improve “practice-based” evidence. Dr. Aidala is coprincipal director and study director of the Community Health Advisory & Information Network (CHAIN), an ongoing study of persons living with HIV or at high risk of infection in New York City, now in its eighteenth year. CHAIN is conducted in collaboration with the HIV Planning Council and the New York Health Department of Health and Mental Hygiene and is a main source of data for service planning in the region. Formerly she directed the Multiple Diagnoses Initiative, a Department of Housing and Urban Development–Department of Health and Human Services joint initiative that worked with housing providers to better understand the reciprocal relationship between housing and health care among persons living with HIV/AIDS who also struggle with mental illness and/or chronic substance abuse problems. Dr. Aidala received her Ph.D. in sociology from Columbia University.
David D. Celentano, Sc.D., M.H.S., is professor and Charles Armstrong Chair of the Department of Epidemiology in the Johns Hopkins Bloomberg School of Public Health, with joint appointments in medicine; international health; and health, society, and behavior. His research integrates behavioral science theory and research with epidemiologic methods in the study of behavioral and social epidemiology. Although originally trained in a chronic disease paradigm (alcoholism and cancer control), he began his research in HIV/AIDS and sexually transmitted diseases (STDs) in the early 1980s. He has worked on some of the major cohort studies (AIDS Link to the Intravenous Experience [ALIVE], Multicenter AIDS Cohort Study [MACS]) in HIV epidemiology, as well as conducted intervention research in the United States for heterosexual men and women, injection drug users, and young men who have sex with men. He began international HIV research in 1990 through a long-term collaboration with Chiang Mai University in northern Thailand. He has worked on and directed numerous HIV/AIDS and STD epidemiological investigations and preventive interventions. He and his collaborators demonstrated that a behavioral intervention with young military conscripts led to a sevenfold reduction in incident STDs and halved the