Key result
During 2017–2018, the frequency of circulating influenza viruses with reduced susceptibility to neuraminidase inhibitors was 0.8%, and 0.08% had substitutions reducing baloxavir susceptibility.
Why the study?
Annual global surveillance was conducted to analyze influenza virus susceptibilities to neuraminidase inhibitors and the newly approved cap-dependent endonuclease inhibitor baloxavir.
Observational (n=15,409)
Yes
The frequency of circulating influenza viruses with reduced susceptibility to neuraminidase inhibitors or baloxavir remained low globally during the 2017-2018 period.
Answers are grounded in this paper and cite their sources.
Low resistance rates support continued NAI and baloxavir use; leaves open need for ongoing global surveillance.
The global analysis of neuraminidase inhibitor (NAI) susceptibility of influenza viruses has been conducted since the 2012–13 period. In 2018 a novel cap-dependent endonuclease inhibitor, baloxavir, that targets polymerase acidic subunit (PA) was approved for the treatment of influenza virus infection in Japan and the United States. For this annual report, the susceptibilities of influenza viruses to NAIs and baloxavir were analyzed. A total of 15409 viruses, collected by World Health Organization (WHO) recognized National Influenza Centers and other laboratories between May 2017 and May 2018, were assessed for phenotypic NAI susceptibility by five WHO Collaborating Centers (CCs). The 50% inhibitory concentration (IC 50 ) was determined for oseltamivir, zanamivir, peramivir and laninamivir. Reduced inhibition (RI) or highly reduced inhibition (HRI) by one or more NAIs was exhibited by 0.8% of viruses tested (n = 122). The frequency of viruses with RI or HRI has remained low since this global analysis began (2012–13: 0.6%; 2013–14: 1.9%; 2014–15: 0.5%; 2015–16: 0.8%; 2016–17: 0.2%). PA gene sequence data, available from public databases (n = 13523), were screened for amino acid substitutions associated with reduced susceptibility to baloxavir (PA E23G/K/R, PA A36V, PA A37T, PA I38F/M/T/L, PA E119D, PA E199G): 11 (0.08%) viruses possessed such substitutions. Five of them were included in phenotypic baloxavir susceptibility analysis by two WHO CCs and IC 50 values were determined. The PA variant viruses showed 6–17-fold reduced susceptibility to baloxavir. Overall, in the 2017–18 period the frequency of circulating influenza viruses with reduced susceptibility to NAIs or baloxavir was low, but continued monitoring is important.
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Takashita et al. (2020) conducted an observational in Influenza virus infection (n=15,409). Neuraminidase inhibitors and baloxavir was evaluated on Reduced inhibition (RI) or highly reduced inhibition (HRI) by one or more NAIs. During 2017–2018, the frequency of circulating influenza viruses with reduced susceptibility to neuraminidase inhibitors was 0.8%, and 0.08% had substitutions reducing baloxavir susceptibility.
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