A study funded by the National Institutes of Health in the US has found the H5N1 bird flu virus could be just one mutation away from being able to spread amongst humans.

Although the authors say the virus needs to overcome multiple other barriers to become an effective disease of humans, and there are no cases reported of infection between people, but there is great concern as the mortality rate for H5N1 bird flu when they impact the human population, is high.

The H5NI influenza virus is a bird flu found in animals worldwide including wild birds.

The study, led by scientists at Scripps Research and published in Science, reveals that a single modification in the virus’ protein would allow for the virus to attach and spread between human respiratory cells.

To cause infection, influenza viruses attach to sugar molecule receptors on cells. Bird flu influenza viruses, in particular, often attach to a unique receptor found in birds but not in the human upper respiratory system.

However, scientists are concerned that the H5N1 virus could evolve to recognise human-type cell receptors, giving them the ability to transmit between people.

“These switches do occur in [bird] flu and it is both interesting and important to recognise that this may also occur in bovine species and may indeed occur in other species and with other viruses,” says Professor Stuart Elborn, Professor of Medicine and Deputy Vice Chancellor at Queen’s University, Belfast.

“Viruses are highly prone to mutations and this is a very well conducted study looking at the science of this, but it is not unexpected that one or two mutations result in the virus having a human specificity.”

Currently, there is an ongoing H5N1 outbreak amongst dairy cattle in the United States, with the disease being detected in at least 282 dairy herds across 14 states.

“[The paper] highlights the need for the current outbreak in cattle in the USA to be taken extremely seriously and for every effort to be made to monitor the evolution of this virus and intervene where possible to limit its opportunities to try out its options of evolving further in humans,” says Professor Ed Hutchison from the University of Glasgow.

As of publishing, the CDC has confirmed 58 reported human cases of H5N1, however there are currently no known cases of transmission between people.

“This is a really important paper,” says Director of The Pandemic Institute, Liverpool, Professor Tom Solomon.

“[It] shows which genetic changes would be necessary to alter this protein making human infection more likely. It also shows the protein structure which allows it to interact with human tissue and cause human infections.”

“The scientific community will continue to monitor changes in the virus’ genetics as it evolves further to help us prepare for any future pandemics.”

The researchers say the results strengthen the need for continued monitoring of genetic variations in H5N1.

“While any new mutations or transmission of a virus can be concerning, it’s important to remember that it also increases our understanding of it, which in turn improves surveillance and vaccine development,” says Professor David Heymann from the London School of Hygiene and Tropical Medicine.

“It’s this broad understanding of a virus that will then help determine the best possible control activities and management of those infected.”

The authors of the study note that other genetic mutations would also likely be required before the virus can dangerously transmit between humans and cause a widespread pandemic.

“We do not yet know whether H5N1 influenza viruses will evolve to become a disease of humans,” says Hutchinson.

“It is very important to note that this mutation is not the only barrier to emergence. As the authors note the virus needs to overcome multiple barriers to become an effective disease of humans.”

The current public health risk is low, according to the CDC which is monitoring and surveilling the situation.

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