The deadly bird flu has infected and killed hundreds, but is believed to be relatively difficult to spread between humans.

If the virus was to take to the air it would most likely claim many more lives, a Cell Press news release reported. The virus has caused outbreaks in poultry 15 counties in Asia and the Middle East. In order for the virus to cause a pandemic it must be able to spread through the air.

Researchers noticed set of mutations in the H5N1 (bird flu) virus that allowed it to become airborne and spread between ferrets.  

"By gaining fundamental knowledge about how the influenza virus adapts to mammals and becomes airborne, we may ultimately be able to identify viruses that pose a public health risk among the large number of influenza viruses that are circulating in animals," senior study author Ron Fouchier of Erasmus Medical Center, said in the news release. "If we can do this, we might be able to prevent some pandemics in the future."

The researchers pinpointed five mutations that can lead to airborne transmission in ferrets, which are "one of the best models of influenza transmissibility available today," the news release reported. Two of these mutations helped the virus bind to the upper respiratory tract of the ferrets. Two of the other mutations helped the virus replicate while the final mutation increased the virus' stability.

"This type of analysis provides a more complete picture of the changes that may constitute increased risk of H5N1 transmissibility," Peter Palese of the Icahn School of Medicine at Mount Sinai, who coauthored an Essay accompanying the research paper, said in the news release. "Assessment of how adaptations in ferrets affect viral fitness, virulence, and transmission is sorely needed in order to gain a truly holistic perspective of the likelihood that these viruses might cause a pandemic and what characteristics such a pandemic might exhibit."