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Oseltamivir-Resistant Flu Viruses Increasing

Resistant viruses pose lethal threat to high-risk patients

TUESDAY, Mar. 3 (HealthDay News) -- The 2008 to 2009 influenza season will see a higher prevalence of oseltamivir-resistant viruses, and certain strains of the virus are highly pathogenic to high-risk patients, according to two studies published online Mar. 2 in the Journal of the American Medical Association. Another study reports that intranasal live attenuated influenza vaccine is associated with more medical encounters than trivalent inactivated vaccine.

Zhong Wang, Ph.D., and colleagues at the Armed Forces Health Surveillance Center in Silver Spring, Md., conducted influenza surveillance among more than one million American military personnel during the three flu seasons from 2004 to 2007, and found that subjects in all three seasons that were vaccinated using trivalent inactivated vaccine had lower incidence of pneumonia and influenza compared to live attenuated influenza vaccination or no vaccination.

Nila J. Dharan, M.D., of the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues tested the 2007-2008 season influenza A(H1N1) viruses, and found that of 1,155 viruses tested, 142 (12.3 percent) of them were resistant to oseltamivir. Preliminary data shows that 264 of 268 samples tested from the 2008-2009 season are also resistant. In another report, Jairo Gooskens, M.D., of Leiden University Medical Center in the Netherlands, and colleagues describe the transmission of oseltamivir-resistant influenza A(H1N1) viruses with the H274Y mutation in stem cell transplant and elderly patients.

"This study confirmed that circulating H274Y mutated A(H1N1) viruses can retain significant pathogenicity and lethality, as shown in these elderly or immunocompromised patients with lymphocytopenia, underlining the urgency for the introduction of new effective antiviral agents and therapeutic strategies," Gooskens and colleagues write.

Abstract - Wang et al
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Abstract - Dharan et al
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Abstract - Gooskens et al
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