Answers are grounded in this paper and cite their sources.
Within 5 months after the earliest detection of human influenza A(H1N1)pdm09 virus, we found molecular and culture evidence of the virus in healthy US show pigs. The mixing of humans and pigs at swine shows possibly could further the geographic and cross-species spread of influenza A viruses.
No takes yet. Share an insight, caveat, or question.
Gray et al. (2012) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: