The avian and human H5N1 viruses causing the "bird flu" outbreak in Hong Kong in 1997 had affinity for binding to SAα2,3Gal but the virus associated with human disease in Hong Kong in 2003 had affinity to bind to both avian-like SAα2,3Gal and human-like SAα2,6Gal [16]. The gene discussed is SAA2; the disease is avian influenza.