Derwent Stainthorpe Whittlesey (1890-1956) There were three major philosophies promoted separately during the past years by medical geographers and epidemiologists.  The first is the sequent occupance theory, which was proposed in 1929 by Derwent Whittlesey (1890-1956).  The second is the epidemiological transition theory promoted by Abdul R. Omran in 1971.  The third is politely referred to as The McKeown Theory … Continue reading Epidemiological Transition