He has studied the AIDS pandemic from the early 1980s in California, where he was responsible for surveillance and control of communicable diseases, to the late 1980s at the World Health Organization in Geneva, Switzerland, where he was responsible for developing the methods and guidelines for global and regional HIV/AIDS surveillance.
He worked as chief of the surveillance, forecasting and impact assessment unit (SFI) of the Global Programme on AIDS, World Health Organization, Geneva, Switzerland from 1987–1992.
Since his resignation from GPA/WHO in 1992, he has worked as an independent consultant for different international agencies to evaluate the patterns and prevalence of HIV in developing countries, primarily in Africa and Asia.
He was a clinical professor of epidemiology at the School of Public Health, University of California at Berkeley, from 1992 until 2009 when he retired from active teaching.
During his public health career, Chin has held leadership positions at state, national, and international organizations and received recognition for his work as an infectious disease epidemiologist.