Most currently recorded H5N1 viruses were concentrated in the fourth-order clades. During this decade, there have been increasing human infections and new glycosite patterns of HA and NA. It has been reported that the H5N1 virus of clade 2.2 was involved in the outbreak that occurred among the migratory bird population near Qinghai Lake in 2005. Since then clade 2.2 spread westward. This resulted in a number of deaths of wild birds in Europe [65] . In 2006, the H5N1 virus appeared in Africa for the first time, followed by hundreds of mortally infected humans in Egypt, Nigeria and Djibouti [66] . Figure 5D , File S3).