miércoles, 25 de noviembre de 2009

Oseltamivir-Resistant Pandemic (H1N1) 2009 Virus | CDC EID

EID Journal Home > Volume 15, Number 12–December 2009

Volume 15, Number 12–December 2009
Oseltamivir-Resistant Influenza A Pandemic (H1N1) 2009 Virus, Hong Kong, China
Honglin Chen, Chung Lam Cheung, Hung Tai, Pengxi Zhao, Jasper F.W. Chan, Vincent C.C. Cheng, Kwok-Hung Chan, and Kwok-Yung Yuen
Author affiliation: The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China

Suggested citation for this article

Resistance to oseltamivir was observed in influenza A pandemic (H1N1) 2009 virus isolated from an untreated person in Hong Kong, China. Investigations showed a resistant virus with the neuraminidase (NA) 274Y genotype in quasi-species from a nasopharyngeal aspirate. Monitoring for the naturally occurring NA 274Y mutation in this virus is necessary.

Emergence of influenza A pandemic (H1N1) 2009 virus, presumably from swine to humans, has spread globally since April 2009 (1–3). This emergence prompted the World Health Organization to declare a pandemic caused by this virus on June 11, 2009. Although most cases of infection are mild or asymptomatic, 1,462 fatal cases were reported to the World Health Organization as of August 6, 2009 (www.who.int/csr/don/2009_09_11/en/index.html).

Experimental evidence from animal models showed that this virus was able to replicate to high titers in the lungs of infected animals (4), unlike seasonal influenza viruses, which mainly infect the upper respiratory tract. Serologic studies found that antibodies induced by current seasonal influenza vaccines show little cross-reactivity to pandemic (H1N1) 2009 virus (5).

Therapeutic options are presently limited to 2 neuraminidase (NA) inhibitors, oseltamivir and zanamivir, because this virus has a swine-origin matrix 2 (M2) gene, which contains a mutation associated with resistance to M2 ion channel blockers amantadine and rimantadine. Although oseltamivir has been widely used in persons infected with pandemic (H1N1) 2009 virus, resistance was not observed until recently. Three unrelated cases of resistance to oseltamivir were observed in Denmark, Japan, and Hong Kong (www.who.int/csr/disease/swineflu/notes /h1n1_antiviral_resistance_20090708/en/index.html).

Emergence of resistance to oseltamivir by seasonal influenza A virus (H1N1) was detected in Norway in 2007. This virus has evolved into the dominant influenza A virus (H1N1) in humans (6). This finding raises strong concerns that the 274Y resistant mutation in pandemic (H1N1) 2009 virus might circulate and become dominant. We report virologic investigation of the emergence of oseltamivir resistance in this virus in a patient from Hong Kong.

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Oseltamivir-Resistant Pandemic (H1N1) 2009 Virus | CDC EID

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