Chinese scientists investigating the spread of airborne influenzas have reportedly combined genetic material from avian (H5N1) and swine (H1N1) flu strains to create more than 100 different hybrid viruses, five of which proved contagious among mammals. Ying Zhang, et al., “H5N1 Hybrid Viruses Bearing 2009/H1N1 Virus Genes Transmit in Guinea Pigs by Respiratory Droplet,” Science, May 2013. According to the study, researchers engineered 127 reassortant viruses using “a duck isolate of H5N1, specifically retaining its hemagglutinin (HA) gene throughout, and a highly transmissible, humaninfective H1N1 virus,” then tested the reassortants in mice “as a correlate for virulence in humans” and in guinea pigs, “which have both avian and mammalian types of airway receptor,” as a test of transmissibility.

The results evidently showed that in addition to H5 HA gene mutations, which “improve affinity for human-like airway receptors,” specific H1N1 genes enhanced mammal-to-mammal transmission, including “the polymerase PA gene and nonstructural protein NS gene”—which made the virus airborne— as well as nucleoprotein, neuraminidase and matrix genes. This outcome suggests that even low-pathogenic strains of avian flu can combine with other viruses “in current agricultural scenarios” to increase both virulence and transmissibility.

“It’s remarkable work and clearly shows how the continued circulation of H5N1 strains in Asia and Egypt continues to pose a very real threat for human and animal health,” Oxford University Clinical Research Director Jeremy Farrar was quoted as saying in a May 3, 2013, Nature article about the findings. At the same time, however, he noted concerns about the creation of such hybrid viruses in laboratory settings, pointing to last year’s controversial decision by the World Health Organization to permit the publication of two studies involving H5N1 strains that were engineered to spread more easily among mammals. “I do believe such research is critical to our understanding of influenza. But such work, anywhere in the world, needs to be tightly regulated and conducted in the most secure facilities, which are registered and certified to a common international standard,” Farrar said. Additional details about the controversy surrounding H5N1 research appear in Issue 428 of this Update.