| Date | Location | Position |
|---|---|---|
| 1954 - 1955 | Mary Imogene Bassett Hospital Cooperstown, New York |
Intern in Medicine |
| 1955 - 1977 | U.S. Public Health Service | Commissioned Officer |
| 1955 - 1957 | Epidemic Intelligence Service (EIS) Assistant to Chief, Epidemiology Branch Communicable Disease Center (CDC) Department of Health, Education and Welfare Atlanta, Georgia |
Chief |
| 1957 - 1959 | Mary Imogene Bassett Hospital Cooperstown, New York |
Resident in Medicine |
| 1960 - 1961 | Epidemiology Branch and Chief, EIS, CDC | Assistant Chief |
| 1961 - 1965 | Surveillance Section, Epidemiology Branch, CDC | Chief |
| 1965 - 1966 | Smallpox Eradication Program, CDC | Chief |
| 1966 - 1977 | Smallpox Eradication Unit World Health Organization Geneva, Switzerland |
Chief Medical Officer |
| 1977 - 1990 | The Johns Hopkins University School of Hygiene and Public Health Baltimore, Maryland |
Dean and Professor of Epidemiology and International Health |
| 1990 - 1993 | The Johns Hopkins University School of Hygiene and Public Health Baltimore, Maryland |
Edgar Berman Professor in International Health |
| 1990 - 2016 | Johns Hopkins Bloomberg School of Public Health Baltimore, Maryland |
Dean Emeritus |
| 1991 - 1993 | Office of Science and Technology Policy, Executive Office of the President Washington, DC |
Associate Director for Life Sciences |
| 1993 - 2016 | Johns Hopkins University Baltimore, Maryland |
University Distinguished Service Professor |
| 1993 - 1995 | Department of Health and Human Services (DHHS) Washington, DC |
Deputy Assistant Secretary for Health and Senior Science Advisor |
| 1998 - 2001 | Johns Hopkins Center for Civilian Biodefense Strategies* Baltimore, Maryland |
Founding Director |
| 2001 - 2002 | Office of Public Health Emergency Preparedness Department of Health and Human Services Washington, DC |
Director, Principal Science Advisor |
| 2002 - 2007 | Office of the Secretary of Health and Human Services Washington, DC |
Principal Science Advisor for Public Health Preparedness |
| 2005 - 2016 | Center for Health Security,* U. of Pittsburgh Medical Center | Distinguished Scholar |
| 2005 - 2016 | U. of Pittsburgh Schools of Medicine and Public Health | 21st Century Professor of Medicine and Public Health |
* * In 2005, the Johns Hopkins Center for Civilian Biodefense Strategies became the University of Pittsburgh Center for Biosecurity. It was renamed the Center for Health Security in 2013, and in 2017 renewed its affiliation with Johns Hopkins.