He then worked at the National Institute of Allergy and Infectious Diseases (NIAID) with respiratory cold viruses.
Johnson moved to the National Institutes of Health (NIH) field laboratory in the Panama Canal Zone, studying hemorrhagic fever agents.
His time at the Centers for Disease Control (CDC) subsequently the Centers for Disease Control and Prevention in Atlanta, led to field work in Africa and Korea, where he established the first completely suited Level-4 laboratory of “special pathogens” for the safe study of viruses capable of infection by the respiratory route.
In 1981, he left the CDC to work for the United States Army Medical Research Institute of Infectious Diseases as the Program Director of Hazardous Viruses.
He has also served as an adjunct professor of Medicine and biology at the University of New Mexico, where his energy is focused on hantaviral disease and ecology.