MMWR is a weekly report from the Centers for Disease Control on public health concerns.
Both CINAHL and Medline are great databases to use for finding nursing and other allied health articles, but generally, using the correct MeSH (medical subject heading) term in Medline or CINAHL term in CINAHL is key. If an index term does not exist for your subject, you can search it as a keyword.
"Explode" is useful in most searches because it includes articles with subheadings to the term you are interested in.
In EBSCO databases, the * is the symbol to use for unlimited truncation. For example, nurs* would return results with nurse, nurses, nursery, and nursing.