New H5N1 bird flu variant poses new risk to public, study says

A new variant of the deadly avian flu virus has prompted countries to ban flights to Russia and to recommend isolating people who have contact with anyone suspected of having the flu, an international research team said Friday.

While no human cases of avian flu have been confirmed, the researchers, based at the Children’s Hospital Boston, warned that some of the same mutations that make another deadly form of avian flu flu even more lethal can produce a mutation that makes the H5N1 strain of avian flu very transmissible between humans.

Writing in the journal Cell, the group says that people are more at risk of becoming infected with this variant of bird flu because they have higher genetic “reservoirs” of the virus in their bodies.

The scientists cautioned that their findings are based on the bird flu strain H5N1, not its 21- or 33-milligram version as it is in the wild. It is the more lethal strain because the genetic mutations made it more susceptible to treatment with antiviral drugs like Tamiflu, but less of a problem because it generally infects less quickly and less heavily. And because this new mutation is even more transmissible than the bird flu virus it affects, the researchers say it could be very dangerous indeed.

But the discovery does raise questions.

“I’m wondering whether it is essential to be aware that the viral strain is also considerably more transmissible,” said Jennifer Renzulli, professor of virology at the University of Texas Southwestern, and not involved in the research. “This is not an automatic basis for fear.”

In an email, she called the discovery “highly surprising,” since we knew of mutations that could affect the viral RNA infectivity and the ability to make the virus transmissible but didn’t know the implications of the different mutations.

It could be important to help people take the antiviral drugs Tamiflu and Relenza if the variant becomes widely circulating, she said. But she added that if that virus first emerged to the effect that it had far higher infectivity than it did in the wild, we could see much more transmissibility.

A team of biologists based at the University of Wisconsin in Madison wrote that the new H5N1 virus is believed to be largely random mutations that would have already occurred within a typical chicken flock somewhere along the line. That made it far less likely to gain a permanent foothold with human hosts.

“We know that it is very unlikely that it would escape and attack people,” said Elise DuBois, a biology professor.

While she said people should treat the discovery like “frightening news,” she said that there are so many viruses causing such infections today, so little chance of it working, that we should not need to be worried by it.

A second small human laboratory study released by the National Institutes of Health confirmed the findings of the latest paper, suggesting that people with weakened immune systems might need to be particularly careful.

“The general public is not at risk,” said Denis Krivosheev, a professor of virology at the University of Minnesota. “For the general public to be at risk of infection with this virus, the virus would need to start establishing a widespread reservoir in humans. This hasn’t happened.”

Leave a Comment