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.
英
美
- 大量证据表明,候鸟可将低致病性病毒传播给鸡群,然后低致病性病毒突变产生高致病性形式。