Perhaps you should try some spelling variations:
"communicable disease" » "communicable diseases"
"complicated diseases" » "complicated cases", "complex diseases", "mediated diseases"
"medical diseases" » "tropical 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: (("communicable disease") OR ((("complicated diseases") OR ("medical diseases")))).
• Removing quotes may allow a broader search: (( communicable disease ) or ((( complicated diseases ) or ( medical diseases )))).
• Adding a wildcard symbol may retrieve word variants: (("communicable disease") or ((("complicated diseases") or ("medical diseases"))))*.