The best way to find Ebooks is with the Medical Ebooks Search. There are subject sets for public health and for epidemiology, so start by picking the one most likely to contain your topic, or search by typing a keyword in the box.
You can also search in the library catalog, click the "Library Search" tab, enter your keyword, and use the filters to narrow the results to certain campus locations, or to electronic resources.
Find the Ejournals by searching for a word in the name of the journal (not by the title of an article). Consider related terms that might be useful. To narrow your retrieval, choose more specific terms; to broaden your search, think of umbrella terms that are on topic but less specific. Remember, you are only searching the name of the journal, not for individual articles (see PubMed for that).