The A/H1N1 <e1>virus</e1> originated in an Asian <e2>bird</e2> that was exported to Mexico, where it may have reassorted in a pig before infecting people.
The A/H1N1 virus originated
The A/H1N1 virus originated in an Asian bird that was exported to Mexico, where it may have reassorted in a pig before infecting people.
<triplet> virus <subject> bird <object> Entity-Origin(e1,e2)