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TUESDAY, May 28 (HealthDay News) -- Chinese scientists say they've identified the first cases of resistance to the flu drug Tamiflu in a person infected with the emerging H7N9 avian flu virus.
According to BBC News, there have been 131 confirmed cases in China of the new "bird" flu in humans so far, including 36 deaths. No new cases have been identified in over two weeks.
According to the new report, published online May 28 in The Lancet, viral samples from three of 14 patients treated for H7N9 in a Shanghai hospital tested positive for resistance to Tamiflu (oseltamivir). These three patients were also the most severely ill -- two died, and the third was still on mechanical ventilation at the time the Lancet paper was published.
"The apparent ease with which antiviral resistance emerges in A/H7N9 [flu] viruses is concerning; it needs to be closely monitored and considered in future pandemic response plans," wrote the team led by Dr. Zhenghong Yuan of Shanghai Medical College of Fudan University, in China, and Dr. Malik Peiris, of the University of Hong Kong.
According to the researchers, the 14 people who are the focus of the report were confirmed to be infected with H7N9 in April, and doctors monitored ongoing viral severity through blood, throat, stool and urine sampling. All of the patients went on to develop pneumonia, and seven got so sick they needed to be placed on ventilators or other technologies to help them take in enough oxygen.
Viral analysis revealed that three of the most severe cases were resistant to neuraminidase inhibitors -- the class of drugs including Tamiflu. Patients who were responsive to these drugs showed a lessening of viral disease and better and quicker recovery, the researchers said.
The three patients whose virus seemed resistant to Tamiflu carried mutations that have been noted in other cases of resistance to the drug. One patient appears to have developed the mutation only after being treated with Tamiflu, suggesting that H7N9 might mutate around the drug with relative ease, the Chinese team said.
-- E.J. Mundell
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SOURCES: The Lancet, news release, May 28, 2013; BBC News