Pigs serve as major reservoirs of H1N1 and H3N2 influenza viruses which are endemic in pig populations world-wide and are responsible for one of the most prevalent respiratory diseases in pigs. The maintenance of these viruses in pigs and the frequent exchange of viruses between pigs and other species is facilitated directly by swine husbandry practices, which provide for a continual supply of susceptible pigs and regular contact with other species, particularly humans. The pig has been a contender for the role of intermediate host for reassortment of influenza A viruses of avian and human origin since it is the only domesticated mammalian species which is reared in abundance and is susceptible to, and allows productive replication, of avian and human influenza viruses. This can lead to the generation of new strains of influenza, some of which may be transmitted to other species including humans. This concept is supported by the detection of human-avian reassortant viruses in European pigs with some evidence for subsequent transmission to the human population. Following interspecies transmission to pigs, some influenza viruses may be extremely unstable genetically, giving rise to variants which could be conducive to the species barrier being breached a second time. Eventually, a stable lineage derived from the dominant variant may become established in pigs. Genetic drift occurs particularly in the genes encoding the external glycoproteins, but does not usually result in the same antigenic variability that occurs in the prevailing strains in the human population. Adaptation of a 'newly' transmitted influenza virus to pigs can take many years. Both human H3N2 and avian H1N1 were detected in pigs many years before they acquired the ability to spread rapidly and become associated with disease epidemics in pigs.
Pigs act as reservoir hosts maintaining H1N1 and H3N2 influenza viruses, with swine husbandry practices sustaining virus persistence and interspecies interfaces that enable transmission to humans and other species.
Pigs serve as major reservoirs of H1N1 and H3N2 influenza viruses which are endemic in pig populations world-wide... The maintenance of these viruses in pigs and the frequent exchange of viruses between pigs and other species is facilitated directly by swine husbandry practices, which provide for a continual supply of susceptible pigs and regular contact with other species, particularly humans.
Geographic raw
world-wide
Reservoir EcologyExtraction confidence 0.75
Key finding
Pigs maintain H3N2 influenza viruses as endemic reservoirs, supported by husbandry interactions that drive ecological persistence and human-animal viral exchange.
Pigs serve as major reservoirs of H1N1 and H3N2 influenza viruses which are endemic in pig populations world-wide... The maintenance of these viruses in pigs and the frequent exchange of viruses between pigs and other species is facilitated directly by swine husbandry practices, which provide for a continual supply of susceptible pigs and regular contact with other species, particularly humans.
Geographic raw
world-wide
Cross Species Transmission1 records
Cross Species TransmissionExtraction confidence 0.95
Key finding
Avian influenza viruses, including H1N1, were transmitted to pigs where they adapted and caused disease outbreaks, indicating animal-to-animal cross-species transmission.
The pig has been a contender for the role of intermediate host for reassortment of influenza A viruses of avian and human origin since it is the only domesticated mammalian species which is susceptible to, and allows productive replication, of avian and human influenza viruses. Both human H3N2 and avian H1N1 were detected in pigs many years before they acquired the ability to spread rapidly and become associated with disease epidemics in pigs.
Transmission direction
animal-to-animal
Genomic Evolution1 records
Genomic EvolutionExtraction confidence 0.80
Key finding
Human-avian reassortant influenza A viruses in pigs exhibit genetic instability and drift in glycoprotein genes, resulting in new stable lineages adapted to pigs.
This concept is supported by the detection of human-avian reassortant viruses in European pigs... Following interspecies transmission to pigs, some influenza viruses may be extremely unstable genetically, giving rise to variants... Eventually, a stable lineage derived from the dominant variant may become established in pigs. Genetic drift occurs particularly in the genes encoding the external glycoproteins.
Human H3N2 and avian H1N1 influenza viruses adapted over time after transmission to pigs, eventually gaining efficient replication and epidemic potential in swine.
Adaptation of a 'newly' transmitted influenza virus to pigs can take many years. Both human H3N2 and avian H1N1 were detected in pigs many years before they acquired the ability to spread rapidly and become associated with disease epidemics in pigs.
Genes or proteins
external glycoproteins
Mechanism types
adaptation; replication_efficiency; pathogenicity
Recombination Or Reassortment1 records
Recombination Or ReassortmentExtraction confidence 0.90
Key finding
Human-avian reassortant influenza A viruses were detected in European pigs, supporting the role of pigs as intermediate hosts for reassortment and cross-species transmission to humans.
The pig has been a contender for the role of intermediate host for reassortment of influenza A viruses of avian and human origin... This concept is supported by the detection of human-avian reassortant viruses in European pigs with some evidence for subsequent transmission to the human population.
Event type
reassortment
Spillover Event1 records
Spillover EventExtraction confidence 0.80
Key finding
Human-avian reassortant influenza A viruses detected in European pigs were subsequently transmitted to humans.
This concept is supported by the detection of human-avian reassortant viruses in European pigs with some evidence for subsequent transmission to the human population.
