I think it's dependent on the specific class. There's a pretty informative thread on the re-app forum titled "Epi course AMCAS classifcation" that should help clear things up. I know I've taken courses like Radiation Biology, Pathologic Basis of Disease, Virology, Bacteriology, etc... (that were all public health classes) and those seem to fit the definition of biology pretty well (not to mention a fair amount of physics in the rad bio course)