Perhaps you should try some spelling variations:
"communicated diseases" » "communicated disease", "communicable diseases", "communicable disease"
"complicated diseases" » "complex diseases", "mediated diseases", "complicated case"
"medical diseases" » "tropical diseases", "viral diseases"

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: (("communicated diseases") OR ((((("complicated diseases") OR ("complicated cases"))) OR ("medical diseases")))).
• Removing quotes may allow a broader search: (( communicated diseases ) or ((((( complicated diseases ) or ( complicated cases ))) or ( medical diseases )))).
• Adding a wildcard symbol may retrieve word variants: (("communicated diseases") or ((((("complicated diseases") or ("complicated cases"))) or ("medical diseases"))))*.