I look for the best and most recent sources of information, and my starting point is the lastest edition of Control of Communicable Diseases Manual (CCDM). The latest edition of Principles and Practice of Infectious Diseases (PPID) edited by Mandell et al. became available in September 2009 with full-text online access, and CCDM became available in 2010. The availability of searchable electronic resources makes the job easier to build and continuously improve lists for differential diagnosis.
IDdx is regularly updated based on the latest editions of PPID, CCDM, CDC Travel, and other peer-reviewed scientific publications. New features added in January 2015 were Ranked Diseases and Weighted Findings. Ranked Diseases means that the user can sort the list of diseases returned from a query by cases/year in either the U.S. or worldwide. Weighted Findings means that color coding indicates how frequently a finding is used to describe the disease in the twelve primary references. Findings are color coded to show if they appear in only 1 book (gray font), 2 books, or 3 or more books. The findings of a disease are included only if they are published in the primary references. Weighted Findings enables another new feature: Query Sensitivity. Choose High to get the most diseases that match one or more signs & symptoms. Choose Low to get only those diseases in which the finding was cited in three or more of the 12 references. This screenshot of Microsoft Access shows how the software enables the color coding of symptoms based on the 12 major references.
The web version of IDdx was developed in early 2020. On July 29, 2020, I completed the process of updating 9 of the 12 main references that are in new editions.