The new bird influenza that’s killed six people in eastern China has some of the genetic hallmarks of an easily transmissible virus, according to the scientist who showed how H5N1 avian flu could become airborne.
The H7N9 strain, which is a new virus formed as a result of two others merging their genetic material, has features of viruses that are known to jump easily from birds to mammals, and a mutation that may help it attach to cells in the respiratory tract, said Ron Fouchier, a professor of molecular virology at Erasmus Medical Center in the Netherlands, in a telephone interview yesterday.
“That’s certainly not good news,” said Fouchier, who reviewed a gene sequencing of H7N9 published by Chinese health authorities. “This virus really doesn’t look like a bird virus anymore; it looks like a mammalian virus.” …
Fouchier authored a study last year that showed five genetic tweaks to the deadly H5N1 virus, which has killed more than 600 people since 2003, made it airborne in ferrets, the mammals whose response to flu most closely resembles that of humans.
One of the mutations he made is in an enzyme called polymerase; another was in a protein called hemagglutinin on the surface of the virus. H7N9 has both mutations, he said.
“This virus is certainly of more concern than the vast majority of bird flu viruses,” Fouchier said. “Most bird flu viruses that we know do not have these mutations.”
Whether those mutations alone are enough to make the virus easily transmissible isn’t clear, and should be “high on the research agenda,” Fouchier said. Still, there’s no evidence yet that the virus is more likely to become more dangerous than H5N1, he said.
“Even if we see relatively high numbers of human cases, it doesn’t mean a pandemic is imminent,” he said. “H5N1 has circulated for 16 years and not become mammal-to-mammal transmissible.” …
Since 2013, the H7N9 bird flu virus has sickened at least 1,562 people in China and killed at least 612.Some 40 percent of people hospitalized with the virus die.
And the number dying during each epidemic has increased dramatically in recent months.
In the first four epidemics, the virus showed few changes. But last flu season, there were some 764 cases – nearly half of the 1,562 total.
Which is why a new risk assessment tool from the U.S. Centers for Disease Control and Prevention ranks H7N9 as the leading animal flu strain with the potential of causing a human pandemic.