They are known to carry viruses of the H5 and H7 subtypes, but usually in the low pathogenic form.

据知，它们携带H5和H7亚型病毒，但通常是低致病性的。

youdao

On present understanding, H5 and H7 viruses are introduced to poultry flocks in their low pathogenic form.

据目前所知，H5和H7型病毒以低致病形式传给禽类。

youdao

Migratory birds can carry these viruses, in their low pathogenic form, over long distances, but do not usually develop signs of illness and only rarely die of the disease.

候鸟可以低致病性方式远距离携带这些病毒，但通常不显示疾病体征并且很少死于该病。

youdao

Considerable circumstantial evidence suggests that migratory birds can introduce low pathogenic H5 and H7 viruses to poultry flocks, which then mutate to the highly pathogenic form.

相当多的旁证表明侯鸟能够传播低致病性禽流感的H5和H7亚型病毒给家禽，然后，变异成高致病性类型。

youdao

Considerable circumstantial evidence suggests that migratory birds can introduce low pathogenic H5 and H7 viruses to poultry flocks, which then mutate to the highly pathogenic form.

相当多的旁证表明侯鸟能够传播低致病性禽流感的H5和H7亚型病毒给家禽，然后，变异成高致病性类型。

youdao