Triple‐reassortant influenza A virus with H3 of human seasonal origin, NA of swine origin, and internal A(H1N1) pandemic 2009 genes is established in Danish pigs

Abstract

This report describes a triple‐reassortant influenza A virus with a HA that resembles H3 of human seasonal influenza from 2004 to 2005, N2 from influenza A virus already established in swine, and the internal gene cassette from A(H1N1)pdm09 has spread in Danish pig herds. The virus has been detected in several Danish pig herds during the last 2‐3 years and may possess a challenge for human as well as animal health.

Swine Influenza A Viruses and the Tangled Relationship with Humans

“…An introduction of a human seasonal H3N2 virus in the late 2000s occurred in Vietnam (Ngo et al 2012), with the lineage subsequently detected in China (He et al 2018). Also, in the 2000s, a human seasonal H3 HA emerged in Danish pigs, reassorted with a swine N2 NA and internal genes from the H1N1pdm09 virus, 2000.3 (Krog et al 2017). Then, during the 2010-2011 human influenza season, a distinct human seasonal H3N2 virus transmitted to U.S. swine and sustained onward transmission (Rajão et al 2015).…”

“…These dynamics contributed to the generation of numerous genetically and antigenically distinct lineages cocirculating in swine around the world. Then, the repercussions of these evolutionary events were starkly shown with the swine-origin pandemic in 2009 (Mena et al 2016), the subsequent impact of the continued 2009 pandemic H1N1 (H1N1pdm09) introductions into pig populations (Nelson et al 2015c), and ongoing detections of contemporaneous human seasonal H3N2 spillovers into swine (Ngo et al 2012;Rajão et al 2015;Krog et al 2017;Wong et al 2018;Zeller et al 2018a). The genetic diversity of H1 and H3 viruses in swine is summarized in Figure 1A,B and the N1 and N2 neuraminidase genes in swine are summarized in Figure 2A,B.…”

A Systematic Review Analyzing the Prevalence and Circulation of Influenza Viruses in Swine Population Worldwide

“…Europe Belgium H1N1, H1N2, H3N2 None [179][180][181] Denmark H1N1, H1N2, H3N2 None [182][183][184] United Kingdom H1N1, H1N2, H3N2, A(H1N1)pdm09, H1N7 IBV, ICV [185][186][187][188][189][190][191][192] Finland H1N1, H1N2, H3N2, A(H1N1)pdm09 None [193,194] France H1N1, H1N2, H3N2, A(H1N1)pdm09 None [195][196][197][198][199] Germany H1N1, H1N2, H3N2, A(H1N1)pdm09 None [200][201][202][203] Greece H1N1, H1N2, H3N2, A(H1N1)pdm09 None [204] Italy H1N1, H1N2, H3N2, A(H1N1)pdm09 IDV [205][206][207][208][209][210][211][212][213][214][215][216][217] Spain H1N1, H1N2, H3N2 None [218][219][220][221] Netherlands H1N1, H1N2, H3N2 None [222] Norway A(H1N1)pdm09 None [223][224]…”

“…Surprisingly, a piglet as young as just three days was found infected with IAV [183]. Two H3N2 isolates having H3 genes from seasonal human influenza along with internal genes that originated from A(H1N1)pdm09 virus and NA genes from contemporary N2 swine influenza viruses that have been in circulation in Denmark were retrieved from young piglets at two locations during 2011-2014 [184]. H3N2 virus was also detected from piglets having respiratory illness and from sows with reproductive problems in commercial piggeries in 2014 [184].…”

The risk of a swine influenza pandemic: still a concern?

“…Such human viruses resulted in sustained transmission in swine, leading to the establishment of novel IAVs lineages in the swine host and contributing to the genetic and antigenic diversity of influenza observed in pigs. For example, a triplereassortant H3N2 virus derived from human seasonal H3N2 viruses and the internal genes from H1N1pdm has recently spread among swine in Denmark and Mexico [3,4]. Humanorigin IAVs have also been reported circulating in pigs across the continents [5,6] including countries with large swine populations like Brazil [7], Vietnam [8] or Chile [9].…”