In an article to be published in the journal Microbial Pathogenesis, Chinese researchers report on a 4 year serological surveillance project of Influenza A on pigs farms in Guangdong, Zhejiang, Fujian, and Yunnan Provinces in Southern China. As the authors note, pigs are believe to be intermediate hosts or mixing vessels of pandemic influenza viruses. Influenza viruses can undergo reassortment in pigs, allowing the virus to adapted to humans and possibly cause a pandemic.
The serological study used haemagglutination inhibition (HI) tests to examine antibodies of H5 and H9 viruses among the samples from pigs. The good news is that the researchers failed to find H5 infections (Clade 2.3.2) within the pig samples. A ressortant H5N1 virus from pigs could easily start the next pandemic. H5 viruses have already infected more than 600 people from numerous countries in the last decade, so an H5N1 pandemic is a serious concern.
The bad news is that the authors found an infection rate of at least 3.7% among the samples from pigs for H9 viruses. H9 viruses also pose a pandemic threat for humans. Another serological study from 2009 in China found that a small percentage of farmers from Xinjiang Uygur autonomous region and Liaoning province tested positive for H9 viruses. A reassortant pandemic virus does not have to originate in a pig, it could originate in a human infected with H9 or H5 viruses.
 Serological surveillance of H5 and H9 avian influenza A viral infections among pigs in southern China