Scientists who created a mutant bird flu virus said Wednesday they will resume the controversial research after taking a 12-month break to allay fears of the bug escaping the lab or falling into terrorist hands.

Citing a “public health responsibility” to continue the work, the teams said research will resume in countries whose governments had given the go-ahead, but not in the United States, which is mulling safety guidelines, nor at US-sponsored research projects in other countries.

Teams in the United States and the Netherlands announced in December 2011 they had engineered a hybrid of the H5N1 bird flu virus that was transmissible by air among mammals— in this case ferrets, which are considered a good research model for humans.

Publication of their results was delayed and their work halted for a year amid concerns that terrorists may lay their hands on the data.

“We fully acknowledge that this research — as with any work on infectious agents — is not without risks,” the scientists wrote Wednesday, following extensive consultation with intelligence, health and security agencies.

“However, because the risk exists in nature that an H5N1 virus capable of transmission in mammals may emerge, the benefits of this work outweigh the risks.”

In its current form, the virus spreads easily among poultry and wild birds but is hard to transmit to humans. It is even harder to pass on from human to human, which has only happened in isolated cases.

Humans mainly contract the virus by handling live or dead infected birds, and there is no evidence of contamination from eating properly cooked poultry.

The scientists' work highlighted the risk of the virus evolving naturally to cause a pandemic in which it can be spread easily from human to human. The research seeks to create models to enable us to deal with a potential human outbreak.

“The lifting of the moratorium by researchers must not be seen as closure of the debate,” it wrote.AFP