The study in mice has shown that the seasonal flu can turn into a highly dangerous form if combined with avian flu.
Yoshihiro Kawaoka, a virologist at the University of Wisconsin-Madison, who led the study, says that some combinations of N5H1 virus known as avian flu and seasonal flu can produce a life-threatening form that is stronger than the original bird flu.
While it is known that some forms of bird flu may cause more serious illness than others. The flu viruses are also able to mutate and they may turn into more pathogenic forms of the virus.
Scientists ay that swine flu known as H1N1 virus may also take part in viral mutations and create a deadly form of flu.
The study was published in the recent issue of the Proceedings of the National Academy of Sciences.