Oseltamivir-resistant influenza viruses circulating during the first year of the influenza A(H1N1) 2009 pandemic in the Asia-Pacific region, March 2009 to March 2010

• Published in: Euro surveillance : bulletin européen sur les maladies transmissibles Vol. 16; no. 3; p. 20
• Main Authors: Hurt, A C, Deng, Y M, Ernest, J, Caldwell, N, Leang, L, Iannello, P, Komadina, N, Shaw, R, Smith, D, Dwyer, D E, Tramontana, A R, Lin, R T, Freeman, K, Kelso, A, Barr, I G
• Format: Journal Article
• Language: English
• Published: Sweden Centre Europeen pour la Surveillance Epidemiologique du SIDA (European Centre for the Epidemiological Monitoring of AIDS) 20.01.2011
• Subjects: Antiviral Agents - pharmacology; Antiviral drugs; Asia - epidemiology; Australia - epidemiology; Drug resistance; Drug Resistance, Viral - genetics; Epidemiology; Genotype & phenotype; Humans; Influenza A Virus, H1N1 Subtype - drug effects; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza, Human - drug therapy; Influenza, Human - epidemiology; Influenza, Human - virology; Inhibitor drugs; Microbial Sensitivity Tests - methods; Mutation; Neuraminidase - antagonists & inhibitors; Neuraminidase - genetics; Oseltamivir - pharmacology; Pacific Islands - epidemiology; Pandemics; Phylogeny; Population Surveillance; Reverse Transcriptase Polymerase Chain Reaction; RNA, Viral - genetics; Sequence Analysis; Swine flu; Time Factors; World Health Organization; Australia; Asia; Pacific Islands; Asia-Pacific region
• ISSN: 1560-7917; 1025-496X; 1560-7917
• DOI: 10.2807/ese.16.03.19770-en

During the first year of the influenza A(H1N1) 2009 pandemic, unprecedented amounts of the neuraminidase inhibitors, predominantly oseltamivir, were used in economically developed countries for the treatment and prophylaxis of patients prior to the availability of a pandemic vaccine. Due to concerns about the development of resistance, over 1,400 influenza A(H1N1) 2009 viruses isolated from the Asia-Pacific region during the first year of the pandemic (March 2009 to March 2010) were analysed by phenotypic and genotypic assays to determine their susceptibility to the neuraminidase inhibitors. Amongst viruses submitted to the World Health Organization Collaborating Centre for Reference and Research in Melbourne, Australia,oseltamivir resistance was detected in 1.3% of influenza A(H1N1) 2009 strains from Australia and 3.1% of strains from Singapore, but none was detected in specimens received from other countries in Oceania or south-east Asia, or in east Asia. The overall frequency of oseltamivir resistance in the Asia-Pacific region was 16 of 1,488 (1.1%). No zanamivir-resistant viruses were detected. Of the 16 oseltamivir-resistant isolates detected, nine were from immunocompromised individuals undergoing oseltamivir treatment and three were from immunocompetent individuals undergoing oseltamivir treatment. Importantly, four oseltamivir-resistant strains were from immunocompetent individuals who had not been treated with oseltamivir, demonstrating limited low-level community transmission of oseltamivir-resistant strains. Even with increased use of oseltamivir during the pandemic, the frequency of resistance has been low, with little evidence of community-wide spread of the resistant strains. Nevertheless, prudent use of the neuraminidase inhibitors remains necessary, as does continued monitoring for drug-resistant influenza viruses.