Hi, Colleen. I don't have an immediate answer for you with respect to online Epid coursework. But, if you also have a need for some background in supporting subjects, such as math or statistics, check out MIT's site for free online courses, at:
I'm back. My alma mater, the University of Michigan School of Public Health, offers an online certificate. This course covers several areas of public health. Further information can be found at:
I can vouch for the quality of the distance learning courses at the London School of Hygiene and Tropical Medicine. Their short certificate courses are top notch too Colleen!