Washington, Nov 19 (ANI): A new study by American and British scientists has tried to explain why bird flu has not become a pandemic disease.

The report prepared by scientists from Imperial College London, the University of Reading and the University of North Carolina, USA, says that bird flu viruses would have to undergo at least two simultaneous genetic mutations before they could be infected from human to the other.

The authors of the study say the possibility of two genetic mutations occurring at the same time is quite remote.

Bird flu or H5N1 has a mortality rate of 60percent in humans but there has been no human-to-human transmission, which could spur a pandemic.

H5 viruses can only infect the ciliated cell in the mouth and nose, and a human-to-human transmission would need it to bind with non-ciliated type of cell as well.

H5N1 is a particularly nasty virus, so when humans started to get infected with bird flu, people started to panic. An H5N1 pandemic would be devastating for global health. Thankfully, we haven't yet had a major outbreak, and this has led some people to ask, what happened to bird flu? We wanted to know why the virus hasn't been able to jump from human to human easily, professor Wendy Barclay, co-author of the study from the Division of Investigative Science at Imperial College London, said.

Prof Barclay added: Our new research suggests that it is less likely than we thought that H5N1 will cause a pandemic, because it's far harder for it to infect the right cells. The odds of it undergoing the kind of double mutation that would be needed are extremely low. However, viruses mutate all the time, so we shouldn't be complacent. Our new findings do not mean that this kind of pandemic could never happen. It's important that scientists keep working on vaccines so that people can be protected if such an event occurs.

Professor Ian Jones, the research team leader from the University of Reading, said: It would have been impossible to do this research using mutation of the real H5N1 virus as we could have been creating the very strain we fear. However, our novel recombinant approach has allowed us to safely address the question of H5 adaptation and provide the answer that it is very unlikely.

The research has appeared in PLoS ONE. (ANI)