Epidemiology: The Basic Science of Public Health is a great fundamental course offered by the University of North Carolina at Chapel Hill. It is a 6-week course covering history of epidemiology, what and how to measure disease frequency, various study designs, measures of association, and causality.

The videos are short and concise. The quizzes are great for catching up with what I just learned from video lectures. The content is quite heavy, but the instruction is well-organized to cover all the fundamental concepts. The definitions of the measures of health outcome are still unclear on my end, but this course was very helpful in learning some basics.

Course information: https://www.coursera.org/learn/epidemiology