But , but experts remain on guard.Acting agency director, Richard Besser, says the epidemic in Mexico promoted prompted U.S. doctors to begin monitoring actively for possible infections.

• 疾病控制与预防中心的代理主任理查德贝塞表示墨西哥猪流感爆发事件让美国的医生警醒，他们开始积极监测可能存在的感染。