前一年，纽约州立大学石溪分校的一个小组复制了脊髓灰质炎病毒。
A team at the State University of New York, in Stony Brook, had made a copy of the polio virus the previous year.
最近的担忧激发了大量研究，我们现在比四年前更加了解流感病毒和大流行问题。
Recent concern has stimulated enormous research, and we know much more about influenza viruses and pandemics than we did four years ago.
科学家认为这种病毒是5年前从马传染到狗身上的，但从未感染过人类。
Scientists believe the virus jumped from horses to dogs 5 years ago, but it has never infected a human.
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