Most H5N1 viruses were grouped into clade 0 before it appeared in Hong Kong again in 2003. Various patterns of the glycosites in HA and NA had co-existed in these original viruses. These original NAs contained the known glycosites, including four highly conserved glycosites in the stalk domain and seven in the global domain (except the occasional 341NGT which only appeared in clade 1 and Thailand records during 2004,2010, e.g., A/chicken/Thailand/CU-354/2008 (H5N1)). In contrast, six highly conserved glycosites together with 170NST exist widely in clade 0. Since 2003, the WHO has recorded a three-wave epidemic of H5N1, which resulted in hundreds of deaths and huge economic losses [11] . Until recently, the glycosite patterns were highly conserved in all the avian clades except for clade 7 (e.g., clade 3, 4, 5, 6, 8 and 9), as shown in Figure 4 and Figure S2 .