Onuma earned her MD at the Yale School of Medicine. She completed her residency and fellowship at Massachusetts General Hospital, followed by an M.Sc. from the Harvard T. H. Chan School of Public Health in 2014. She served as a Medical officer in charge of Cardiovascular Disease management at the World Health Organization in Geneva, Switzerland, and returned to Yale in 2019 as an assistant professor and associate director of the Yale Preventive Cardiovascular Health Program and an affiliated faculty member at the Yale Institute for Global Health.She joined the faculty at MGH and Harvard Medical School in 2023 and is the founding director of the MGH Global Cardiovascular Health Program.

A prolific researcher, she co-authored the American College of Cardiology expert consensus decision pathway earlier this year on the clinical evaluation and management of patients hospitalized with COVID-19. Dr. Onuma is the author of multiple publications on global health and cardiovascular disease prevention in Stroke, Lancet, Circulation, and the New England Journal of Medicine, among others.