Multiple Reassortment between Pandemic (H1N1) 2009 and Endemic Influenza Viruses in Pigs, United States

Mariette Ducatez,Adam Rubrum ,Daniel Darnell ,David Wang ,James Lowe ,Randy R Simonson ,Kevin Juleen ,Jeri‐Carol Crumpton ,Cesar Corzo ,Christy Brockwell‐Staats ,Marie Gramer ,Ben M Hause ,Ashley Webb ,Evelyn Stigger-Rosser ,Richard J Webby

doi:10.3201/eid1709.110338

Abstract

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. Field observations suggested that the newly described reassortant viruses did not differ substantially from pandemic (H1N1) 2009 or endemic strains in their ability to cause disease. Comparable growth properties of reassortant and endemic viruses in vitro supported these observations; similarly, a representative reassortant virus replicated in ferrets to the same extent as did pandemic (H1N1) 2009 and endemic swine virus. These novel reassortant viruses highlight the increasing complexity of influenza viruses within pig populations and the frequency at which viral diversification occurs in this ecologically important viral reservoir.

Highlights

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not
The pandemic virus was first detected in pigs in Canada in early May 2009 [2], and at least 14 countries have reported pigs infected with pandemic (H1N1) 2009 viruses [3], a few of which have been thoroughly described in the literature: in the Americas
Of the 9 viruses, 8 displayed HA and NA genes of endemic swine influenza viruses and pandemic (H1N1) 2009 M gene segments; the origin of the remaining gene segments differed depending on the virus (Figure 1)

Summary

Introduction

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Comparable growth properties of reassortant and endemic viruses in vitro supported these observations; a representative reassortant virus replicated in ferrets to the same extent as did pandemic (H1N1) 2009 and endemic swine virus. These novel reassortant viruses highlight the increasing complexity of influenza viruses within pig populations and the frequency at which viral diversification occurs in this ecologically important viral reservoir. The pandemic virus was first detected in pigs in Canada in early May 2009 [2], and at least 14 countries have reported pigs infected with pandemic (H1N1) 2009 viruses [3], a few of which have been thoroughly described in the literature: in the Americas

Methods

Results

Conclusion