[Pigs as intermediate hosts for new reassortant influenzae viruses with zoonotic potential]

Swine influenza, due to swine influenza viruses (SIV) H1N1, H3N2 and H1N2, has become enzootic in densely pig-populated areas worldwide. Several genetic lineages can be distinguished within each subtype, as pigs are susceptible to both avian and human influenza viruses and can generate reassortant viruses. SIV is a zoonotic pathogen. Transmission to humans is usually without symptoms, but some cases of severe infections have been reported. Pandemic virus (H1N1) 2009 contains a new gene constellation originating from several SIVs and has acquired an efficient inter-human transmission capacity. Pigs being also very susceptible to this pandemic virus, it could adapt to swine and further reassort with other influenza viruses. This emergence again poses the question about the role played by pigs as an intermediate host for the adaptation of avian viruses to mammalian hosts and the generation of new reassortant viruses. Thus, it is necessary to reinforce surveillance of SIV for Public Health and Animal Health issues. Factors that limit interspecies transmission and adaptation to a new host are polygenic but poorly understood as yet.