TUESDAY, July 16 (HealthDay News) -- Some strains of the new H7N9 bird flu virus that appeared in China this year are resistant to antiviral drugs, and tests can fail to identify that resistance, which could help accelerate their spread, a new study finds.
"We'd better get some vaccine seed stocks up and ready. The antiviral option for controlling H7N9 isn't too good," said study corresponding author Robert Webster, of St. Jude Children's Research Hospital in Memphis, Tenn.
Researchers analyzed viruses taken from the first person known to have H7N9 infection and found that 35 percent of them were resistant to Tamiflu (oseltamivir) and Relenza (zanamivir), which are antiviral drugs used to treat H7N9 infections.
However, lab testing of the viruses failed to detect the strains that were resistant, so using lab tests to monitor the development of resistance in H7N9 would be useless, according to the authors of the study, published July 16 in the online journal mBio.
Resistant strains of H7N9 can flourish in patients treated with oseltamivir or zanamivir, inadvertently leading to the spread of resistant infections, explained Webster.
"If H7N9 does acquire human-to-human transmissibility, what do we have to treat it with until we have a vaccine? Oseltamivir. We would be in big trouble," he said in a journal news release.
H7N9 first appeared in China in early 2013, in some cases infecting people who had been in contact with poultry or had been in places where poultry are housed. The virus has since been detected in poultry at live markets near where human infections have been reported. As of July 12, the number of H7N9 infections was 132 and the number of deaths 43.
The U.S. Centers for Disease Control and Infection has more about the H7N9 virus.