643. Surveillance for Oseltamivir-Resistant Influenza A(H1N1)pdm09 Virus Infections during 2015-2016, United States
Session: Poster Abstract Session: Oh, Those Pesky Viruses!
Thursday, October 27, 2016
Room: Poster Hall
Background: Since A(H1N1)pdm09 emerged, the prevalence of oseltamivir-resistant A(H1N1)pdm09 viruses in US has been <2%. All oseltamivir-resistant viruses contain an H275Y substitution in the neuraminidase (NA). During 2013-14, 57% of oseltamivir-resistant viruses were unrelated to prior oseltamivir use and 11/60 (18%) contained additional NA substitutions (termed “permissive”) at V2411, N369K, and N386K that are thought to prevent a H275Y-induced reduction in virus fitness. We describe findings from US surveillance for oseltamivir-resistant A(H1N1)pdm09 viruses during 2015-16.

Methods: The Centers for Disease Control and Prevention requested state public health laboratories to submit up to 8 virus isolates (2 of each subtype/lineage) every 2 weeks for NA inhibition assay testing and 5 additional A(H1N1)pdm09 clinical specimens for pyrosequencing for H275Y. NA sequencing was performed on resistant viruses. A standard case form was collected from all persons infected with oseltamivir-resistant A(H1N1)pdm09.

Results: From October 1, 2015 to May 5, 2016, 1832 A(H1N1)pdm09 clinical specimens and virus isolates were tested. Overall, 14 (0.8%) oseltamivir-resistant A(H1N1)pdm09 were detected from 8 states; all contained H275Y. Full length NA sequences were completed for 4 cases; all 4 contained the 3 permissive NA substitutions (V241I, N369K, and N386K). None of the 14 A(H1N1)pdm09 viruses were resistant to zanamivir. The 14 patients had a median age of 48 years (range 9 months - 85 years); 5 (36%) reported no exposure to oseltamivir prior to specimen collection, 8 were taking oseltamivir at the time of specimen collection, and oseltamivir receipt was unknown for 1. Eight (57%) of the 14 patients with resistant virus infection were hospitalized, 7 had an immunosuppressive condition, and 5 died.

Conclusion: During the 2015-16 influenza season, oseltamivir-resistant A(H1N1)pdm09 infections were rare but this virus continued to circulate at low levels in the community and was in some cases unrelated to drug use. Permissive NA substitutions were identified in all viruses for which full length NA sequences were available. Ongoing surveillance for trends in oseltamivir-resistant H1N1pdm09 is critical to inform clinical care and public health policies.

Sarah Spencer, PhD1, Ha Nguyen, PhD2, Anwar Abd Elal, BS2, Angela P. Campbell, MD, MPH, FPIDS1, Jennifer Laplante, PhD3, Kristen St. George, PhD4, Larisa Gubareva, MD, PhD1 and Alicia M. Fry, MD, MPH1, (1)Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (2)Centers for Disease Control and Prevention, Atlanta, GA, (3)New York State Department of Health, Albany, NY, (4)Wadsworth Center, New York State Department of Health, Albany, NY


S. Spencer, None

H. Nguyen, None

A. Abd Elal, None

A. P. Campbell, None

J. Laplante, None

K. St. George, None

L. Gubareva, None

A. M. Fry, None

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