英语语法分析

But what is more curious is this: the retrovirus is closely related to a free-living virus called Jaagsiekte sheep retrovirus, which causes lung cancer in sheep and goats, but not other species.

不过更奇怪的是：这种逆转录病毒与一种游离生活的绵羊肺腺瘤逆转录病毒(可以引起绵羊和山羊患肺癌)而不是其它种更加接近。