Well, first of all your current Table structure does not support all scenarios and this kind of query results.
Change it to:
MstDiseases
DID Name
1 Maleria
2 Typhoid
MstSymptoms
SID Name
1 Fever
2 Cold
3 Cough
TrnDiseaseSymptom
TID DID SID
1 1 1
2 1 2
3 2 1
4 2 3
Now, I would like to try the SQL query yourself. It should be much simpler now. Try!
Hint: Use TrnDiseaseSymptom table to get the disease ID's...