Starts every February viral disease via unpleasant vapours (8)
I believe the answer is:
effluvia
'unpleasant vapours' is the definition.
'effluvia' can be an answer for 'vapours' (I have seen 'disagreeable vapours' mean 'effluvia' so perhaps 'vapours' could also mean 'effluvia'). I am not certain of the 'unpleasant' bit.
'starts every february viral disease via' is the wordplay.
'starts' suggests taking the first letters.
'viral disease' becomes 'flu' (I've seen this before).
The first letters of 'every february' is 'ef'.
'ef'+'flu'+'via'='EFFLUVIA'
Can you help me to learn more?
(Other definitions for effluvia that I've seen before include "nasty vapours" , "Nasty smells" , "disagreeable vapours" , "Unpleasant discharges" , "nasty exhalations" .)