A Cluster of Patients Infected with I221V Influenza B Virus Variants with Reduced Oseltamivir Susceptibility--North Carolina and South Carolina, 2010-2011.

Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA, USA.
The Journal of Infectious Diseases (Impact Factor: 5.85). 12/2012; DOI: 10.1093/infdis/jis776
Source: PubMed

ABSTRACT Background. During 2010-2011, influenza B viruses with a novel neuraminidase substitution, denoted I221V, (B/I221V) associated with reduced in vitro oseltamivir susceptibility were detected in North Carolina (NC).Methods. We determined the prevalence of I221V among B viruses submitted to CDC for antiviral resistance surveillance, including all B viruses submitted to NC and South Carolina (SC) state laboratories, during October 2010-September 2011.We conducted chart reviews and phone interviews to characterize NC and SC patients with B/I221V versus wild-type B virus infection (B/WT).Results. We detected I221V in 45 (22%) of 209 B viruses from NC and 8 (10%) of 82 B viruses from SC. We detected I221V in three (0.3%) of 881 B viruses tested from 45 other states. B/I221V infection was not associated with differences in underlying conditions or illness severity compared with B/WT infection. No patients with B/I221V infection received oseltamivir prior to specimen collection. Among patients who completed oseltamivir, those with B/I221V infection reported a longer duration until illness resolution (5 versus 3 days); P=0.02.Conclusions. B/I221V co-circulated with B/WT in NC and SC during 2010-2011. I221V did not alter illness severity but may have reduced oseltamivir effectiveness. Thus, global surveillance for I221V is important.

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