A ProMED-mail post (May 28, 2009)
The following is [1] a statement of the research program of the United States Department of Agriculture (USDA) Agricultural Research Service (ARS), and [2] the outcome of a study of the cross-reactivity of serum samples from US pigs against the new swine origin 2009 H1N1 influenza virus (S/O H1N1). The results of this analysis indicate that pre-existing immunity induced by swine influenza viruses circulating in the US may not protect pigs against the new S/O H1N1 influenza virus presently circulating in people.