In 2011, scientists discovered they had created a highly contagious and deadly form of H5N1 – commonly called avian or bird flu. When the discovery was announced, debate erupted over whether the research was ethical and fears the new strain could be used as a bioterrorism weapon. Now, the World Health Organization has weighed in on the issue.

The WHO said it is deeply concerned about the potential consequences of the research that can make H5N1 more contagious among humans. At the same time, it said “studies conducted under appropriate conditions must continue” so critical knowledge can be gained on reducing the risks posed by the virus.