The epidemiology of avian influenza viruses (AIVs) has undergone a revolution in the past 10 years (Alexander, 2007). Previously, the outbreaks were confined in time and space; today AIVs have become an increased international concern. This unprecedented situation resulted in the failure to control and eradicate infections in poultry due to highly pathogenic avian influenza (HPAI) H5N1 and low pathogenic avian influenza (LPAI) H9N2 viruses. Moreover new reassortments implying AIVs, like the new H7N9 strains that recently caused human deaths in China and the novel H1N1 human virus that became pandemic in 2009, represent a serious threat to public health.