Perhaps you should try some spelling variations:
"communicate diseases" » "communicable disease", "communicate disabled", "communicate discover"
"complicated diseases" » "complex diseases", "mediated diseases", "complicated case"
"communicated disease" » "communicable disease", "communicate state", "communicated vision"

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: (((("communicable diseases") OR ((("communicate diseases") OR ((("complicated diseases") OR ("complicated cases"))))))) OR ((("communicable diseases") OR ("communicated disease")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"communicable diseases\") or (((\"communicate diseases\") or (((\"complicated diseases\") OR (\"complicated cases\"))))))) or (((\"communicable diseases\") or (\"communicated disease\"))))".
• Removing quotes may allow a broader search: (((( communicable diseases ) or ((( communicate diseases ) or ((( complicated diseases ) OR ( complicated cases ))))))) or ((( communicable diseases ) or ( communicated disease )))).
• Adding a wildcard symbol may retrieve word variants: (((("communicable diseases") or ((("communicate diseases") or ((("complicated diseases") OR ("complicated cases"))))))) or ((("communicable diseases") or ("communicated disease"))))*.