On rare occasions, avian influenza viruses have crossed the species barrier to infect humans.

在极少数情况下，禽流感病毒已跨越物种屏障，感染人类。

Mankind, it seems, was just unlucky that this virus made the leap across the species barrier.

似乎这种病毒得以跨越物种的障碍传染到人类身上仅仅是出于人类的不幸。

Pigs are flu sponges, capable of contracting both bird and human viruses that can jump across the species barrier, Richt says.

里希特说，猪是流感海绵，能够跨跃物种界线吸取人类和禽类的流感病毒。

Avian influenza viruses are highly species-specific, but have, on rare occasions, crossed the species barrier to infect humans.

禽流感病毒具有高度物种特异性，但偶尔也跨越物种屏障，感染人类。

Some of these AI viruses have also been reported to cross the species barrier and cause disease or subclinical infections in humans and other mammals.

也有报告称，某些禽流感病毒跨越物种界限传播，并导致人类和其他哺乳动物患病或亚临床感染。