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Antiviral resistance surveillance in Japan (as of June 18, 2025)

Influenza Research Center, National Institute of Infectious Diseases

The table below summarizes the results of genotypic assays for antiviral resistance markers and phenotypic assays for antiviral susceptibility.

For neuraminidase inhibitors, viruses are classified as resistant if phenotypic testing demonstrates a >100-fold reduction in susceptibility for influenza A viruses or a >50-fold reduction for influenza B viruses, in accordance with the criteria established by the World Health Organization (WHO) Expert Working Group on Surveillance of Influenza Antiviral Susceptibility (WHO-AVWG) for the Global Influenza Surveillance and Response System (GISRS).

For cap-dependent endonuclease inhibitors, viruses are considered to have reduced susceptibility if phenotypic testing reveals a >3-fold reduction in susceptibility, based on interim criteria from the WHO-AVWG.

For M2 inhibitors, only genotypic results for resistance markers are reported.

2024/2025 influenza season

(as of June 18, 2025)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：18KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：24KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：23KB）

2023/2024 influenza season

(as of June 18, 2025)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：18KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：26KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：35KB）

2022/2023 influenza season

(as of June 18, 2025)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：18KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：24KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：35KB）

2021/2022 influenza season

(as of February 2, 2023)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：82KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：77KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：78KB）

2020/2021 influenza season

(as of July 27, 2021)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：82KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：78KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：79KB）

2019/2020 influenza season

(as of August 18, 2021)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：119KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：92KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：81KB）

2018/2019 influenza season

(as of December 27, 2019)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：62KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：61KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：48KB）

2017/2018 influenza season

(as of September 24, 2019)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：62KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：62KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：48KB）

2016/2017 influenza season

(as of January 27, 2020)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：59KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：50KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：46KB）

2015/2016 influenza season

(as of January 27, 2020)

Table 1. Detection of antiviral drug-resistant viruses in Japan, [A(H1N1)pdm09, A(H3N2), B]（PDF：59KB）
Table 2. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by prefecture（PDF：58KB）
Table 3. Detection of A(H1N1)pdm09 viruses with H275Y mutation in Japan, Report by week（PDF：47KB）

2014/2015 influenza season

(as of March 4, 2016)

2013/2014 influenza season

(as of April 23, 2015)

2012/2013 influenza season

(as of March 10, 2014)

2011/2012 influenza season

(as of April 11, 2013)

2010/2011 influenza season

(as of February 6, 2013)

2009/2010 influenza season

(as of February 6, 2013)

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