New H7N9 bird flu resistant to anti-virals

New strain of bird flu resistant without limiting ability to spread

December 11, 2013

Scientists have found that a mutation in a new strain of bird flu infecting people in China can render it resistant to a key first-line treatment drug without limiting its ability to spread in mammals.

Dr. Nicole Bouvier, an assistant professor of medicine, infectious diseases at the Icahn School of Medicine at Mount Sinai in New York, said it was not uncommon for influenza viruses to develop genetic mutations that make them less susceptible to anti-flu drugs, but these mutations also usually result in the virus weakening its ability to replicate and spread from person-to-person.

The discovery means that unlike seasonal flu strains, the new H7N9 bird flu does not lose any of its spreading potential with drug resistance to drugs like Roche’s Tamiflu.

While this does not make H7N9 any more likely to develop into a human pandemic, researchers said it means doctors should be prudent in their use of anti-viral medicines to treat H7N9 cases, and consider using drugs other than Tamiflu, such as GlaxoSmithKline’s Relenza, where possible.

“It’s important to emphasize that these H7N9 viruses seem to transmit fairly inefficiently overall,” said Bouvier, who led the H7N9 study which was published in the journal nature Communications on Tuesday.

No vaccine is available to prevent H7N9, which infected at least 135 people and caused 44 deaths during an outbreak. In the absence of a vaccine, anti-viral drugs are the only means of defense for patients who are infected with new strains of the flu.

“In this outbreak, we saw some differences in the behavior of H7N9 and other avian influenza strains that can infect humans, beginning with the rapid development of anti-viral resistance in some people who were treated with oseltamivir and the persistence of high viral loads in those patients,” Bouvier said in a statement.

A team of researchers in the United States said this week that while it is not impossible that H7N9 could become easily transmissible from person to person, it would need to undergo multiple mutations to do that. So scientists around the world are keeping a watchful eye, on alert for any sign the virus might develop such potential.

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