Six potential N-glycosylation sites have been conserved in the N2 NA Danish dataset from 1999 to 2003. The majority of isolates from 2003 to 2006 have lost the site at position 93 which is located in a CTL epitope (HLA-A*0201) region of NA [12] . The recent NAs may therefore be more easily recognised by the cytotoxic immune system. We found two predicted N-glycosylation sites (61 and 70) in the N2 NA stalk region in sequences from 1999-2006. Greater density of carbohydrate in the stalk region of NA might reflect a need for proteolytic protection. The two observed carbohydrates in the stalk have been reported for other isolates in other time periods and other continents [58, 60] . The stalk region has therefore stayed unchanged and the two sequons seem to be conserved.