WEDNESDAY, Dec. 28 (HealthDay News) -- World Health Organization researchers are reporting an apparent spike in Australia in the number of seasonal influenza cases resistant to Tamiflu, the most commonly used antiviral drug.
The jump in such cases involving the pandemic 2009 A(H1N1) flu strain, also known as swine flu, took place during Australia's most recent winter: May through August of 2011.
"In 2007/2008, a different A(H1N1) influenza virus developed Tamiflu-resistance," explained WHO research scientist Aeron C. Hurt, who reported the spike. "On that occasion, it was first detected in large numbers in Europe. However, within 12 months the virus had spread globally, such that virtually every A(H1N1) virus around the world was resistant to this drug," he explained.
"This previous situation demonstrated the speed and potential for a Tamiflu-resistant virus to spread worldwide," Hurt added. "Our concern is that this current pandemic 2009 A(H1N1) Tamiflu-resistant virus may also spread globally."
Hurt, who is based in the Collaborating Centre for Reference and Research on Influenza in North Melbourne, outlined his observations in the Dec. 29 issue of the New England Journal of Medicine.
To explore the question of H1N1-drug resistance, Hurt and his team obtained viral samples from 182 H1N1 flu patients (aged from one month to 74 years) who were being cared for either in an emergency department or an intensive care unit, or by their general practitioner, during the recent winter in Australia.
In all, 29 of the patients (or 16 percent) were found to have a form of H1N1 that was resistant to both Tamiflu (oseltamivir) and an older class of adamantine treatments (rimantadine and amantadine).
Subsequent lab tests revealed that it would take more than 500 times the concentration of Tamiflu usually prescribed for nonresistant flu strains just to cut key a
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