Creating a “hybrid flu” may seem outlandish or irresponsible without additional information. Researchers in China engineered viruses with mixed genetic pieces to mimic a dramatic type of evolution that occurs in nature if a single animal is simultaneously infected with two viruses at once. The studies were done by highly trained personnel in secured bio-safety facilities in non-human animal models. The work gives important clues to how the dangerous H5N1 avian flu may evolve into a more contagious human threat, and how to track the strain if it does evolve. Importantly, the research here is not related to the bird flu virus (H7N9) spreading through China, but the emergence of H7N9 emphasizes why understand the evolution of new viruses is necessary.
This story has interesting parallels to the controversial work performed by the Fouchier group (Netherlands) and Kawaoka group (USA). The earlier studies examined the evolution of H5N1 avian flu as it was transferred between ferrets. The evolved H5N1 gained airborn transmission in ferrets – which have a respiratory tract similar to humans – but the strain was less pathogenic. The genetic changes in the transmissible H5N1 will help researchers track the natural emergence of dangerous viruses, and design appropriate vaccines.
The Chen group studying how H5N1 avian flu may evolve by mixing with other viruses – such as the H1N1 swine flu virus. The mix-matched viruses are called ‘reassortants’, and some of the viruses produced by the scientists demonstrated airborne transmission in guinea pigs. Importantly, guinea pigs have respiratory tracts more like birds, so the research cannot reveal the threat a ‘reassorted’ H5N1/H1N1 virus will pose to humans. Vaccinated humans may be resistant to these types of reassortants.
Special thanks to Ann Fiegen from the Harvard Virology program for her prospective and knowledge on the topic.