Bird Flu Just One Mutation Away From Pandemic

A new study suggests that the H5N1 bird flu virus circulating among U.S. cattle is just one specific mutation away from binding more easily to human cells, “a prerequisite for human-to-human transmission” to become a pandemic.

“In its current form, H5N1 is more capable of infecting certain species of animals than humans,” says study co-author James Paulson, a professor in the Department of Molecular Medicine at Scripps Research in California. “It has infected millions of birds, cattle and dairy cows in the United States, but a relatively small number of people.”

Bird Flu Fears

According to Time magazine, most human cases have been among farm workers.

This suggests that while bird flu isn’t very good at infecting humans, it sometimes finds a way in when people are exposed to high concentrations of it, such as through close contact with sick animals.

But according to New Scientist, a single mutation could allow it to infect the cells lining the human nose and throat, making it more likely to be airborne.

This change alone is not enough for the virus to be capable of causing a pandemic. However, if a virus carrying this mutation swaps genes with a human flu virus, it could gain the ability to cause a pandemic almost immediately.

“The more people it infects, the more likely it is that something like this will happen,” says Ian Wilson of the Scripps Research Institute in California. Despite this, Wilson believes the risk remains low.

The first step in the process

His team focused on the first step in the process, how the virus needs to change in order to bind easily to human cells.

In the lab, they studied a synthetic form of a gene from the virus strain currently circulating in cows.

They performed targeted mutations to see how the changes altered its ability to bind to human cells.

“The surprising finding is that one specific mutation seemed to be enough,” says Paulson. Previous research on H5N1, including Paulson’s, has suggested that more changes will be needed.

Health officials are monitoring the situation closely, and some worrying observations have already been documented.

Transmission between humans

Recently, a Canadian teenager was hospitalized with bird flu. When scientists sequenced the virus from the teenager, they found that it had mutated in a way that might make it more transmissible between humans, similar to the mutation Paulson’s team identified in their study.

Fortunately, the teenager does not appear to have infected anyone else.

While there is no evidence of human-to-human spread yet, Paulson says health authorities should prepare for a wider outbreak of bird flu as a precaution. He says it’s worth stockpiling bird flu vaccines and making plans for how to distribute them if they become necessary.