The virus in the first case originated with poultry and has not mutated. It has no biological features for human-to-human transmission, said Mao Qunan.

• 毛群安说，第一例死亡病例标本分离到的病毒分析显示，病毒仍然是禽源性的，没有发生本质性的变异，不具备人传人的生物学基础。