He also served as head of the All-Union Society of Microbiologists, Epidemiologists and Infectionists. Modern epidemiologists use informatics as a tool. Cohort effects are important to epidemiologists searching for patterns in illnesses. Koch's postulates have been recognized as largely obsolete by epidemiologists since the 1950s. This mathematical impact is well understood by epidemiologists, and is easy to see in theory. Past Chief Epidemiologists of Michigan include Professor Matthew Boulton of the University of Michigan. In his time at the LSHTM he worked with many pioneering epidemiologists, including Donald Reid. For epidemiologists, the key is in the term inference.