美国发现的感染猪流感病人没有直接接触过猪.CDC说这种感染可能是大范围内的人-人传染个案.

　　Can Swine Flu Spread From Person to Person?

　　The U.S. residents infected with swine flu virus had no direct contact with pigs. The CDC says it's likely that the infections represent widely separated cycles of human-to-human infections.