Newspaper article The Canadian Press

Study Warns Drug Resistance Develops Easily with New H7N9 Bird Flu

Newspaper article The Canadian Press

Study Warns Drug Resistance Develops Easily with New H7N9 Bird Flu

Article excerpt

Study warns of drug resistance with H7N9 flu


TORONTO - Resistance to the main flu drug Tamiflu seems to develop with some ease in infections with the new H7N9 bird flu, a concerning new study says.

The work, published in the journal The Lancet, suggests that if this virus were to become easily transmitted among people, there might be minimal tools with which to fight it.

H7N9 viruses are already resistant to the only other class of flu medication, the adamantane drugs. And study of other H7 viruses suggests vaccines made to protect against this flu family do not induce high levels of protective antibodies.

In this work, the authors report that in 14 H7N9 patients in Shanghai, two developed resistance to oseltamivir, the generic name for the drug Tamiflu.

"The apparent ease with which antiviral resistance emerges in H7N9 viruses is concerning; it needs to be closely monitored and considered in future pandemic response plans," wrote the authors, from Shanghai Public Health Clinical Centre and the University of Hong Kong.

This is not the only evidence to suggest resistance to Tamiflu and related drugs may arise easily among H7N9 viruses. The genetic sequence of the first spotted H7N9 patient showed a mutation that is known to confer drug resistance in other flu viruses.

And doctors in Taiwan have reported isolating drug-resistant viruses from an H7N9 patient there. That man was infected in China but returned home to Taiwan and was treated there.

The combination of these signs is worrying, said Dr. Malik Peiris, one of the authors and the chair of microbiology at the University of Hong Kong.

"Obviously this is something that arises not very frequently but not infrequently. And that's enough to be quite concerning," Peiris said in an interview.

It is likely the resistance would also be seen to other drugs in the same class as Tamiflu, the neuraminidase inhibitors. Other drugs in this class include zanamivir (sold as Relenza) and peramivir.

In the paper, Peiris and his co-authors cite as yet unpublished data that shows that the mutation lowers the effectiveness of Tamiflu by 100-fold, but only lowers the effectiveness of zanamivir by 30-fold. "Thus, IV (intravenous) zanamivir should be a viable option for therapy of these patients," he said.

The authors said early use of Tamiflu or other drugs in that class is still the best approach for treating these cases when they arise. …

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