From Mike Coston at Avian Flu Diary, who as always posts excellent article and review, excerpt :
" Although they are only rarely detected, there is evidence to suggest that humans may be infected by avian influenza viruses more often than commonly suspected.
Every year billions of people around the world experience flu-like symptoms that can stem from any of hundreds of different viruses.
Of those, only the tiniest fraction are tested to see what pathogen caused the illness.
While most people are aware of the several hundred H5N1 `bird flu’ infections detected over the past decade, we’ve also seen a smaller number of human infections caused by a variety of avian and swine origin flu viruses."