what does "subjects" mean here?
Hi, what does "subjects" mean here?

"How do we even find subjects to test pain limits so we can quantify pain?"

And what does "sporadic cases" mean
" The CDC reports that hardly anyone dies of tetanus due to the shots we have, but sporadic cases do happen from time to time"

Question

what does "subjects" mean here?
Hi, what does "subjects" mean here?

"How do we even find subjects to test pain limits so we can quantify pain?"

And what does "sporadic cases" mean 
" The CDC reports that hardly anyone dies of tetanus due to the shots we have, but sporadic cases do happen from time to time"

Answer

The 'subjects' is used to replace the word 'participant', or 'volunteer'.  So, it was hard to find volunteers (or participants) to assist with the research on quantifying perceptions of pain.

'Sporadic'  means occasional in this context.