Hog in the Limelight: Swine Flu's Got New Genes On

The new strain, which came from a pig imported from mainland China, has been found in only one animal, and there's no indication that it is particularly virulent. Still, pig farms in several countries have reported infection from humans to pigs of the novel H1N1, indicating that it can easily move back into its original host. And of particular concern is the fact that pig cells are uniquely receptive to influenza viruses from swine, humans, and birds, making swine a dangerous "mixing vessel" for new variants.

Peiris and his co-workers declined to discuss the findings in detail because they have submitted a paper for publication that describes the new virus. But he said the finding underscores a point that he and many colleagues have been shouting from the rooftops since the swine flu pandemic surfaced: Most regions of the world—including North America and Europe—are far too lax about routinely checking pigs for novel flu viruses. "We need much more intensive surveillance in pigs globally," contends Peiris, adding that such reassortments are likely occurring outside China.

A report published online on 3 March by the Journal of Infectious Diseases similarly calls for increased surveillance of humans who work in the commercial hog industry. This report from the Public Health Agency of Canada's National Microbiology Laboratory describes a novel swine influenza found in three workers at a Saskatchewan hog farm. The never-before-described virus did not involve the novel H1N1 but instead picked up the surface genes from the seasonal human H1N1 virus that has long infected humans and combined them with what's known as the triple-reassortant swine influenza. The virus did not appear to spread from human to human but once again proved that the triple-reassortant swine influenzas—a family the novel H1N1 belongs to—are unusually promiscuous and need to be watched carefully.