The HA and neuraminidase (NA) genes are closely related to 2016/2017 swine influenza viruses
from the United States.
Pigs are well known as genetic mixing vessels for human and avian influenza viruses (1,2), and swine influenza viruses
(SIVs) occasionally infect humans (3-5).
While workers reportedly spent only a limited amount of time in the affected swine barns each day, and the number of workers entering each barn daily was small, the fact that half of the farms tested positive for influenza virus in aerosols, surfaces, and/or swine oral fluids suggests that exposure to swine influenza viruses
was taking place and may be significant enough to result in infection.
One of the various types of swine influenza viruses
(SIV) cause swine influenza, also known as pig influenza, swine flu, hog flu, and pig flu.
Swine influenza viruses
caused a pandemic in humans in 2009.
The emergence of novel swine influenza viruses
in North America.
The current H1N1 influenza virus represents a quadruple re-assortment of two swine flu strains, one human and one avian strain of influenza viruses, the largest proportion of genes coming from swine influenza viruses
Contemporary vaccines against Porcine Reproductive and Respiratory Disease Syndrome viruses (PRRSV) and Swine Influenza viruses
(SIV) are composed of either live attenuated viruses that risk frequent recombination between viral and vaccine strains and reversion to virulence or inactivated viruses that confer short term immunity.
However, due to insufficient surveillance of swine influenza viruses
, exact reassortment events are yet to be investigated (11).
Different influenza virus strains display clearly different preference for sialyl linkages at the C-2 position catalyzed by specific sialyltransferases: human and classical swine influenza viruses
prefer to bind sialic acids attached to galactose by [alpha]2-6 linkage, 55),56) whereas avian and equine viruses prefer sialic acids with [alpha]2-3 linkage instead; Fig.
Phylogenetic analysis of the isolated influenza virus was carried out to ascertain genetic relatedness with other known human and swine influenza viruses
Andrew McCammon made a computer movie of slight structural shifts that can occur in the neuraminidase 1 enzyme (the N1 in H1N1), a protein found in avian and swine influenza viruses