Most public health courses will require you to cite in AMA style. AMA style requires reference lists to be arranged in numerical order. In-text citations consist only of the numbers in subscript. Every reference in the reference list must be cited somewhere in the article, and every reference cited in the article must be present in the reference list. If there is a discrepancy, query the author.
Ask your instructor what their preferred citation style is. Some more general citation styles include MLA, APA and Chicago Style.