Scientists believe they have identified a gene that stops humans from becoming infected with bird flu viruses.

Known as BTN3A3, this gene is expressed in the airways, and has been shown in the lab to stop avian flu viruses from spreading by making copies of itself.

The researchers said their work, published in the journal Nature, could help identify new and emerging viruses that have the potential to cause a pandemic.

Professor Massimo Palmarini, director of the MRC-University of Glasgow Centre for Virus Research(CVR), who also led the study, said: “We know that most emerging viruses with human pandemic potential come from animals.

“It is therefore critical to understand which genetic barriers might block an animal virus from replicating in human cells, thereby preventing infection.

We know that most emerging viruses with human pandemic potential come from animals

“Of course viruses are constantly changing and can potentially overcome some of these barriers by mutating over time.

“This is why virus genetic surveillance will be crucial to help us better understand and control the spread of viruses with zoonotic and pandemic potential.”

Bird flu is a disease that is spread among ducks, chickens, turkeys and quails.

There are many different strains of bird flu virus but four have caused concern in recent years: H5N1 (since 1997), H7N9 (since 2013), H5N6 (since 2014), H5N8 (since 2016).

While these viruses do not infect people easily and are not usually spread from human to human, there have been several cases around the world, leading to a number of deaths.

The H7N9 virus, for example, has infected more than 1,500 individuals, with more than 600 fatal cases.

Identifying BTN3A3 resistant variants when they first emerge in birds might help prevent human infections

The researchers said they found that the H7N9 virus has genetic mutations that allow it to “escape” the protective effect of the BTN3A3 gene.

The experts also tracked the evolution of bird flu strains and found that all the human flu pandemics, including the 1918 Spanish flu which caused more than 25 million deaths worldwide, and the swine flu in 2009, were caused by viruses resistant to BTN3A3.

Dr Rute Maria Pinto, the first author of the study, said: “Identifying BTN3A3 resistant variants when they first emerge in birds might help prevent human infections.

“Control measures against emerging avian flu viruses can be tailored specifically against those that are BTN3A3-resistant, in addition to other genetic traits known to be important for zoonotic transmission.”

But the researchers said there are still gaps in scientific knowledge that make it difficult to predict which bird flu viruses might spill over into the humans and when, but added their work on the BTN3A3 could provide a stepping stone.

Prof Palmarini added: “As we go further with our knowledge, there will be a point where from the genetic sequence of a virus, we will be able to characterise all the risks of what it is that this virus can do.

“We are not quite there yet and this is a piece of the puzzle that will contribute to get there.”