Dr. Zaki, who was both a physician and a PhD scientist, combined clinical know-how with the expertise of a laboratory investigator as he sought to solve a host of medical mysteries. As the founder and chief of the CDC’s Infectious Disease Pathology Branch, he was at the forefront of efforts to identify numerous deadly diseases, including the hantavirus, West Nile virus, the Ebola and Zika viruses, severe acute respiratory syndrome (SARS) and the current global pandemic of covid-19.