Swine IAV can cause sporadic zoonotic infections posing a potential risk to human health. The first evidence of zoonotic transmission of human H1N1 to pigs came from the analytic workup of the Spanish flu in 1918. However, no further human-pig H1N1 infection was subsequently demonstrated in Europe until 2009.
The pandemic (H1N1) virus first occurred in a herd of pigs in Canada in 2009 and after that spread worldwide in human and swine. It triggered the seasonal H1N1 virus in humans and is therefore included in human flu vaccines.
In autumn 2011, cases of a zoonotic infection with the porcine H3N2 virus ('H3N2v') were observed in North America. A total of 426 cases were reported in the USA until 2017.
The risk of contracting infection by eating pork containing porcine IAV is negligible. Swine IAV is confined to the animal's respiratory tract; the virus has not been detected in muscle tissue, even in the course of an influenza infection.
Besides the pathogens involved in PRDC, other factors that affect animals' health status are housing conditions, pig house climate, environmental influences and herd management.
In a study presented recently, Fablet et al. in France showed that the likelihood of detecting antibodies to swine IAV in animals increased if more than two groups of animals were present in the vicinity.
Other influences identified were stocking density in the weaning and fattening house, temperature during farrowing, a short suckling period and the absence of strict all-in all-out management (Fablet et al. 2013).
Besides optimising these additional factors, it is important to restrict access to herds.
Information about economic losses can be found here.