Mark S. Riddle, M.D., DrPH, MPH&TM, is Chair of the Department of Preventive Medicine and Biostatistics at the Uniformed Services University of the Health Sciences in Bethesda, Maryland. Born in Modesto, California, he earned dual Bachelor of Science degrees in Zoology and Human Development from the University of California, Davis, graduating cum laude. He went on to complete an M.D. and a Master of Public Health with a specialization in Tropical Medicine at Tulane University, followed by a residency in General Preventive Medicine and Public Health at USUHS. He also holds a Certificate in Clinical Tropical Medicine and Travelers’ Health, completed the advanced vaccinology course at the Fondation Mérieux and University of Geneva, and earned his Doctor of Public Health degree from USUHS in 2007.

After medical school, Dr. Riddle served in the U.S. Navy, including as a shipboard surgeon with the 2nd Battalion, 11th Marines, 1st Marine Division, where he deployed in desert, maritime, and field training environments. He later joined the Naval Medical Research Center’s Enteric Disease Department, eventually directing the Department of Defense’s bacterial diarrhea vaccine research program. He also served as head of the Research Epidemiology Unit at the U.S. Naval Medical Research Unit No. 3 in Cairo, Egypt, where he led disease surveillance and outbreak response efforts across multiple countries, including critical support during a Marburg hemorrhagic fever outbreak.

Dr. Riddle’s research focuses on the pathogenesis, prevention, and treatment of acute enteric infections, the development of vaccines and therapeutics, and the long-term health consequences of gastrointestinal infections. He has helped define disease burden, advanced vaccine development for major enteric pathogens, and pioneered interdisciplinary research that bridges epidemiology, clinical science, and global health. His work reflects a career dedicated to improving both military and civilian health through preventive medicine and translational science.