Perhaps you should try some spelling variations:
"communicate diseases" » "communicated disease", "communicable disease", "communicate disabled"
"complicated diseases" » "complicated cases", "complex diseases", "complicated case"
"mediated diseases" » "related diseases", "medical diseases", "related disease"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("communicate diseases") OR ((("complicated diseases") OR ("mediated diseases"))))) OR ("communicable diseases")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"communicate diseases\") or (((\"complicated diseases\") OR (\"mediated diseases\"))))) or (\"communicable diseases\"))".
• Removing quotes may allow a broader search: (((( communicate diseases ) or ((( complicated diseases ) OR ( mediated diseases ))))) or ( communicable diseases )).
• Adding a wildcard symbol may retrieve word variants: (((("communicate diseases") or ((("complicated diseases") OR ("mediated diseases"))))) or ("communicable diseases"))*.