Dr. Cassell is Senior Lecturer, Department of Global Health and Social Medicine, Harvard Medical School. She is a member of the National Academy of Medicine (NAM) of the National Academy of Sciences, served two terms on the governing board and founded the Forum on Drug Discovery, Development and Translation. She is former Vice President for Scientific Affairs and Distinguished Lilly Research Scholar of Infectious Diseases and former Vice President for Infectious Diseases Drug Discovery and Development of Eli Lilly and Company. Prior to moving to Lilly in 1997, Dr. Cassell was the Charles H. McCauley Professor and Chair of the Department of Microbiology at the University of Alabama Schools of Medicine and Dentistry at Birmingham, a department which ranked first in research funding from the National Institutes of Health (NIH) during the decade of her leadership. She obtained her B.S. from the University of Alabama in Tuscaloosa and in 1993 was selected by that institution as one of the top 31 female graduates of the Centennial following the admission of the first female to the University in 1893. She obtained her Ph.D. in Microbiology from the University of Alabama at Birmingham and was selected as its 2003 Distinguished Alumnus. She is a past President of the American Society for Microbiology and is currently serving her second elected term on the Board of Governors of the American Academy of Microbiology.
Dr. Cassell is an elected lifetime member of the U.S. Council on Foreign Relations. She was named to the original Board of Scientific Councilors of the Center for Infectious Diseases, Centers for Disease Control (CDC) and served as Chair of the Board. She has served on the Advisory Board of the of the Director of NIH, Director of CDC, and the Secretary of Health and Human Services Advisory Council of Public Health Preparedness, the Food and Drug Administration's (FDA) Science Board, the Advisory Committee to the Commissioner. She was a member of the NIH Science Management Board and Advisory Councils of the National Institute of Allergy and Infectious Diseases and the Fogarty International Center of NIH. For two decades she was a member of the Steering Committee of the U.S.-Japan Cooperative Medical Sciences Program responsible for advising the respective governments on joint research agendas, (U.S. State Department/Japan Ministry of Foreign Affairs). She was instrumental in establishment of the U.S./Russia Cooperative Medical Sciences and Training Program under the Bilateral Presidential Commission in 2009 which was a collaboration involving NIH, the US National Academy of Sciences, the Russian Academy of Sciences, and the Russian Academy of Medical Sciences. In 2012, the American Society for Microbiology and the Federation of European Microbiology Societies established the Mäkelä–Cassell Exchange Program for pioneering international engagement for young scientists.