An open API for real-time access to epidemiological surveillance data maintained by the Carnegie Mellon University Delphi research group. The Epidata API contains: COVIDcast API that provides daily updates about COVID-19 activity across the United States, and data about other epidemics including influenza, dengue, norovirus. The COVIDcastAPI includes data about testing, cases, and death, healthcare, and survey data from multiple sources at counties, states, metropolitan statistical areas, and other geographical divisions. Several API clients are available for common programming language like R and Python. Source code available on GitHub: https://github.com/cmu-delphi/delphi-epidata