You are the medical officer of a PHC in Kerala and you confirm the diagnosis of polio in one of your patients. This can be considered as:

Here this disease is an unusual occurrence in the community and is clearly in excess of the expected frequency. So even a single case of polio is an epidemic as per definition. A sporadic case means the case occurs irregularly, haphazardly from time to time and generally infrequent. Ref: Park, Edition 21, Page - 89