Depending on the search tool that you are using (catalog, database, web search), you may need to search for multiple terms. Here are some terms to consider for both textword and subject searching (remember that some databases have specific subject terms to use).
Combine the above terms with terms like these:
or with terms that are disease/condition-specific (like diabetes, gout, etc.)
Here is a list of recommended web resources about health issues of rural and urban populations.