Bug? Some believe epidemic's over (5)
I believe the answer is:
peeve
'bug?' is the definition.
(both can mean to annoy)
'some believe epidemic's over' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'over' is a reversal indicator.
'eveep' is hidden in the letters of 'believe epidemics'.
'eveep' in reverse letter order is 'PEEVE'.
(Other definitions for peeve that I've seen before include "Cause to be annoyed, irritated, or resentful" , "Annoy, get at, irritate" , "cause irritation" , "grouse" , "upset" .)