Funnily enough - every year people in the UK seem to get even more infections (be it Flu, colds or Norovirus/tummy bugs) usually starting end of Nov - Mid Jan.
From what I can remember - there wasn't that many Viruses or Bacterial Infections around Christmas 15-20 years ago.
And strangely enough every time there's yet another batch of the UK population who are told they need a flu jab - or flu spray up their nose, based on some dodgy study - and then sent a threatening letter about how important it is mid Sept/Oct - the number of people sick around Christmas time goes up yet again due to their general populations weakened immune systems
It's got even worse these last 2 years since they started needlessly spraying Fluenz up kids noses - almost every kid I know has been sick either slightly before, during or just after Xmas this year and last year - and the NHS must have the figures to prove it somewhere.