Chinese flu researchers Yoshihiro Kawaoka and Ron Fouchier will create mutant forms of the new H7N9 bird flu strain to study how the flu passes between people.

The virologists have done this before, creating mutant strains of the H5N1 bird flu that could pass easily between ferrets, according to The LA Times. The H7N9 virus is another deadly strain circulating China, having killed 43 of the more than 130 infected individuals.

Reuters reports that although the genetic modification will mean that there will be highly transmissible and deadly forms of H7N9 across several laboratories with high biosecurity levels, Kawaoka and Fouchier say that it is vital to the possibly pandemic threat. The scientists say the only way to find out how likely it is for the virus to rise to pandemic levels is to genetically engineer the highly transmissible form to see how many genetic changes and mutations it will take to get there.

According to CBS News, there has already been a report of a father and daughter both dying from the same strain of H7N9, but scientists do not yet believe the virus had mutated to a form where it can transmit between humans.