Influenza A(H1N1)pdm09 Virus with Reduced Susceptibility to Baloxavir, Japan, 2024

• Published in: Emerging infectious diseases Vol. 31; no. 5; pp. 1019 - 1022
• Main Authors: Takashita, Emi, Morita, Hiroko, Nagata, Shiho, Fujisaki, Seiichiro, Miura, Hideka, Ikeda, Tatsuya, Komabayashi, Kenichi, Sasaki, Mika, Matoba, Yohei, Takahashi, Tomoko, Ogawa, Naomi, Mizuta, Katsumi, Ito, Sueshi, Kishida, Noriko, Nakamura, Kazuya, Shirakura, Masayuki, Watanabe, Shinji, Hasegawa, Hideki
• Format: Journal Article
• Language: English
• Published: United States Centers for Disease Control and Prevention 01.05.2025
• Subjects: Acids, Carbocyclic; Adolescent; Antiviral Agents - pharmacology; Antiviral Agents - therapeutic use; Antiviral drugs; baloxavir acid; baloxavir marboxil; cap-dependent endonuclease inhibitor; Dibenzothiepins - pharmacology; Dispatch; Drug dosages; Drug Resistance, Viral - genetics; Health planning; Humans; Infections; Infectious diseases; Influenza; Influenza A Virus, H1N1 Subtype - drug effects; Influenza A Virus, H1N1 Subtype - genetics; influenza virus; Influenza, Human - drug therapy; Influenza, Human - epidemiology; Influenza, Human - virology; Japan - epidemiology; Microbial Sensitivity Tests; Morpholines - pharmacology; Neuraminidase - antagonists & inhibitors; Oxazines - pharmacology; Patients; Public health; Pyridines - pharmacology; Pyridones - pharmacology; Thiepins - pharmacology; Thiepins - therapeutic use; Triazines - pharmacology; Triazines - therapeutic use; Viruses; Japan; influenza; viruses; polymerase acidic protein; Japan; I38N substitution; respiratory infections; baloxavir marboxil; antimicrobial resistance; influenza virus; A(H1N1)pdm09; cap-dependent endonuclease inhibitor; drug resistance; baloxavir acid
• ISSN: 1080-6040; 1080-6059; 1080-6059
• DOI: 10.3201/eid3105.241123

Influenza A(H1N1)pdm09 virus carrying an I38N substitution was detected in an untreated teenager in Japan. The I38N mutant virus exhibited reduced susceptibility to baloxavir but remained susceptible to neuraminidase inhibitors and showed reduced growth capability. Monitoring antiviral drug susceptibility of influenza viruses is necessary to aid public health planning and clinical recommendations.