Okay, it seems that even once I thought I had sorted out the semantics of flu I still had it wrong!
H1N1 is a subtype, not a strain, and has been around for a while. This new one they are worried about is a strain of H1N1 - and seems currently to be just being referred to as 'swine flu' - even though there are many other swine flus ...
(Thanks Mum for the corrections. lol.)