Multiple reassortment between pandemic (H1N1) 2009 and endemic influenza viruses in pigs, United States.

As a result of human-to-pig transmission, pandemic influenza A (H1N1) 2009 virus was detected in pigs soon after it emerged in humans. In the United States, this transmission was quickly followed by multiple reassortment between the pandemic virus and endemic swine viruses. Nine reassortant viruses representing 7 genotypes were detected in commercial pig farms in the United States.

Genetic composition of contemporary swine influenza viruses in the West Central region of the United States of America.

Background: Because of continuous circulation in different animal species and humans, influenza viruses have host-specific phenotypic and genetic features. Reassortment of the genome segments can significantly change virus phenotype, potentially generating virus with pandemic potential. In 2009, a new pandemic influenza virus emerged.

Diversity of influenza viruses in swine and the emergence of a novel human pandemic influenza A (H1N1).

The novel H1N1 influenza virus that emerged in humans in Mexico in early 2009 and transmitted efficiently in the human population with global spread has been declared a pandemic strain. Here we review influenza infections in swine since 1918 and the introduction of different avian and human influenza virus genes into swine influenza viruses of North America and Eurasia. These introductions often result in viruses of increased fitness for pigs that occasionally transmit to humans.