Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 21, Number 1—January 2015

Oseltamivir-Resistant Influenza A(H1N1)pdm09 Viruses, United States, 2013–14

Margaret Okomo-Adhiambo, Alicia Fry, Su Su, Ha T. Nguyen, Anwar Abd Elal, Elizabeth Negron, Julie Hand, Rebecca J. Garten, John Barnes, Xu Xiyan, Julie M. Villanueva, Larisa GubarevaComments to Author , and 2013–14 US Influenza Antiviral Working Group
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (M. Okomo-Adhiambo, A.M. Fry, S. Su, H.T. Nguyen, A.A Elal, R.J. Garten, J. Barnes, X. Xiyan, J.M Villanueva, L.V. Gubareva); Atlanta Research and Education Foundation, Atlanta (S. Su); Battelle Memorial Institute, Atlanta (H.T. Nguyen, A.A. Elal); Pennsylvania Department of Health, Harrisburg, Pennsylvania, USA (E. Negron); Louisiana Office of Public Health, New Orleans, Louisiana, USA (J. Hand)

Main Article

Table 1

Neuraminidase inhibitor susceptibility for influenza A(H1N1)pdm09 viruses, United States, October 1, 2013–April 30, 2014*

Method of testing Neuraminidase inhibitor
Oseltamivir Zanamivir Peramivir Laninamivir
Neuraminidase inhibition assay†
No. virus isolates tested‡ 1,811 1,811 1,431 352
No. oseltamivir susceptible (mean IC50 ± SD, nmol/L) 1,792 (0.19 ± 0.14) 1,811 (0.18 ± 0.06) 1,412 (0.06 ± 0.02) 352 (0.23 ± 0.08)
No. oseltamivir resistant, (mean IC50±SD, nmol/L) 19 (181.31 ± 67.63) 0 19 (17.71 ± 6.83) 0
Resistance, % 1.1 0 1.3 0
No. clinical specimens tested 3,157 NA 3,157 NA
No. H275 wild-type 3,117 NA 3,117 NA
No. H275 variants 40 NA 40 NA
Resistance, % 1.3 NA 1.3 NA
No. virus tested 4,968 1,11 4,588 352
No. resistant viruses 59 0 59 0
Resistance, % 1.2 0 1.3 0

*IC50, 50% inhibitory concentration; NA, not applicable.
†H275Y confirmed in virus isolate by pyrosequencing and full neuraminidase sequencing.
‡Most (99.8%) influenza A(H1N1)pdm09 virus isolates were characterized as A/California/7/2009-like, the influenza A (H1N1) component of the 2013–2014 Northern Hemisphere influenza vaccine.
§Includes pyrosequencing data from New York contract laboratory and data submitted by 19 state public health laboratories in Arizona, California, Colorado, Delaware, Florida, Georgia, Hawaii, Idaho, Maine, Maryland, Massachusetts, Michigan, Minnesota, New York, Pennsylvania, Texas, Utah, Washington, and Wisconsin.

Main Article

1Members of the 2013–14 US Antiviral Working Group are listed at the end of this article.

Page created: December 19, 2014
Page updated: December 19, 2014
Page reviewed: December 19, 2014
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.