Bird Flu Resistance Worries

H7N9 bird flu study showed some virus resistance to antiviral drugs like Tamiflu

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) There is not yet a vaccine available to prevent the new bird flu strain seen in China, and doctors are still trying to determine the best way to treat patients with the virus.

A new study showed that while the currently preferred method of using common antiviral medications (like Tamiflu) is still the best treatment option, there is evidence of the virus developing resistance to these drugs in some cases.

"Wash your hands frequently."

For their study, Zhenghong Yuang, PhD, of the Shanghai Medical College of Fudan University, Malik Peiris, MD, of the University of Hong Kong, and colleagues followed 14 patients with H7N9.

The patients were admitted to the Shanghai Public Health Clinical Centre between April 4 and April 20, 2013. The patients received antiviral treatment in the form of oseltamivir (Tamiflu) or peramivir.

Samples from the patients’ throats, stools, serum and urine were examined to determine the levels of the virus present in their system (viral load) throughout their treatment.

As the cases progressed, all of the patients developed pneumonia, seven needed help breathing through mechanical ventilation and three needed assistance to both the cardiac and respiratory systems in the form of extracorporeal membrane oxygenation (ECMO).

Two of the patients receiving ECMO eventually died and the third was still dependent on this treatment at the time the study was published.

The researchers found that antiviral treatment was associated with reduced viral load in 11 of the 12 surviving patients.

However, the three patients who required ECMO had “persistently high viral load in the throat in spite of antiviral therapy.”

The authors also found a virus mutation in two patients that is associated with resistance to antiviral drugs. Both of these patients also received corticosteroid treatment.

The authors wrote that since oseltamivir treatment was associated with a reduced viral load in most of the patients, they strongly recommended early treatment with these antiviral drugs in suspected or confirmed cases.

However, the authors also stressed, “The emergence of antiviral resistance in A/H7N9 viruses, especially in patients receiving corticosteroid therapy, is concerning, needs to be closely monitored, and considered in pandemic preparedness planning.”

The latest counts from the World Health Organization (WHO) show a total of 131 cases of H7N9, 36 of which resulted in deaths. No new cases have been confirmed since May 8.

The study was published on May 28 by The Lancet. No conflicts of interest were reported.

Reviewed by: 
Review Date: 
May 28, 2013
Last Updated:
August 9, 2013