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Oseltamivir-resistant influenza virus A (H1N1), Europe, 2007/08 season.

Meijer, A., Lackenby, A., Hungnes, O., Lina, B., Werf, S. van der, Schweiger, B., Opp, M., Paget, J., Kassteele, J. van de, Hay, A., Zambon, M. Oseltamivir-resistant influenza virus A (H1N1), Europe, 2007/08 season. Emerging Infectious Diseases: 2009, 15(4), 552-560

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Influenza Surveillance

Findings

- In Europe, the 2007/08 winter season was dominated by influenza virus A (H1N1) circulation through week 7, followed by influenza B virus from week 8 onward.
- Oseltamivir-resistant influenza viruses A (H1N1) (ORVs) with H275Y mutation in the neuraminidase emerged independently of drug use.
- By country, the proportion of ORVs ranged from 0% to 68%, with the highest proportion in Norway. The average weighted prevalence of ORVs across Europe increased gradually over time, from near 0 in week 40 of 2007 to 56% in week 19 of 2008 (mean 20%).
- Neuraminidase genes of ORVs possessing the H275Y substitution formed a homogeneous subgroup closely related to, but distinguishable from, those of oseltamivir-sensitive infl uenza viruses A (H1N1).
= Minor variants of ORVs emerged independently, indicating multiclonal ORVs.

Overall, the clinical effect of ORVs in Europe, measured by infl uenza-like illness or acute respiratory infection, was unremarkable and consistent with normal seasonal activity. (aut. ref.)