The southern Chinese province of Guangdong is the source of the H5N1 avian flu virus, according to a genetic analysis of the virus published Monday by the University of California Irvine. The researchers concluded that Guangdong is the origin of renewed waves of the H5N1 strain, which has killed 167 people worldwide as well as causing the death or forced destruction of millions of birds, Reuters reported. By creating a road map or family tree of the quickly mutating virus, the hope is that scientists can find the most suitable strain for making a vaccine. The research showed that Qinghai province in northwest China is another key source of bird flu's spread. Meanwhile, China's Ministry of Agriculture ordered the immunization of all domestic poultry during spring, when the virus is at its most contagious. The vaccination campaign must begin before March 15 and end before May. For more, see China Economic Review's special report this month.