Perhaps you should try some spelling variations:
"complicated diseases" » "complicated cases", "complex diseases", "complicated case"
"communicable disease" » "communicable diseases"
"communicated disease" » "communicable diseases", "communicate state", "communicated vision"
"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: (((((("complicated diseases") OR ("mediated diseases"))) OR ("communicable disease"))) OR ("communicated disease")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((\"complicated diseases\") OR (\"mediated diseases\"))) or (\"communicable disease\"))) or (\"communicated disease\"))".
• Removing quotes may allow a broader search: (((((( complicated diseases ) OR ( mediated diseases ))) or ( communicable disease ))) or ( communicated disease )).
• Adding a wildcard symbol may retrieve word variants: (((((("complicated diseases") OR ("mediated diseases"))) or ("communicable disease"))) or ("communicated disease"))*.