The OSC group studied 253 samples of the virus collected from the Osaka area during the initial phase (May 2009) and from the Kansai and Kanto areas during the peak phase (October 2009 to January 2010) of contagion.
Of the 20 different mutation groups identified in the peak infection group, analysis revealed that 12 were entirely new to Japan.
Rapid mutation of the virus strains was traced to a genome with an extremely high evolutionary rate.
Among the variety of mutants discovered, the researchers were able to pinpoint two mutations which clearly differentiate the early phase and peak phase viruses.
They also identified mutations in some viruses which confer resistance to Oseltamivir (Tamiflu), one of the most widely-used antiviral drugs.
While yielding valuable clues on the genetic origins of drug resistance, the findings may pave the way toward the development of new diagnostic kits for detecting and preventing the spread of global pandemic diseases.
