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Which influenza virus subtypes have been isolated from pigs?
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influenza
A colored transmission electron micrograph showing influenza viruses (red) at the outer surface of a host cell.
Several influenza A virus subtypes have been isolated from pigs, which serve as important reservoirs for these viruses. The subtypes identified in swine populations include:12
- H1N1: First isolated from pigs in 1930, this remains a significant subtype associated with swine flu.1
- H1N21
- H3N11
- H3N2: This subtype emerged in pigs in the late 1990s and is suspected to have been transmitted to them from humans.1
These viruses are characterized by the composition of their surface proteins, hemagglutinin (H) and neuraminidase (N). Because pigs can be simultaneously infected with different strains—such as those originating from humans, birds, and other swine—they are uniquely positioned to facilitate genetic reassortment, a process that can lead to the emergence of new influenza strains.12