{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,10]],"date-time":"2026-09-10T06:02:01Z","timestamp":1789020121209,"version":"build-2803163510"},"reference-count":27,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2020,1,29]],"date-time":"2020-01-29T00:00:00Z","timestamp":1580256000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100009619","name":"Japan Agency for Medical Research and Development","doi-asserted-by":"publisher","award":["JP18am001007"],"award-info":[{"award-number":["JP18am001007"]}],"id":[{"id":"10.13039\/100009619","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100009619","name":"Japan Agency for Medical Research and Development","doi-asserted-by":"publisher","award":["JP19fk0108056"],"award-info":[{"award-number":["JP19fk0108056"]}],"id":[{"id":"10.13039\/100009619","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100009619","name":"Japan Agency for Medical Research and Development","doi-asserted-by":"publisher","award":["JP19fk0108104"],"award-info":[{"award-number":["JP19fk0108104"]}],"id":[{"id":"10.13039\/100009619","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100009619","name":"Japan Agency for Medical Research and Development","doi-asserted-by":"publisher","award":["JP19fm0108006"],"award-info":[{"award-number":["JP19fm0108006"]}],"id":[{"id":"10.13039\/100009619","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["19K06399"],"award-info":[{"award-number":["19K06399"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]},{"name":"NIAID-funded Center for Research on Influenza Pathogenesis","award":["CRIP, HHSN272201400008C"],"award-info":[{"award-number":["CRIP, HHSN272201400008C"]}]},{"name":"Grants-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Science, Sports, and Technology (MEXT) of Japan","award":["16H06429, 16K21723, and 16H06434"],"award-info":[{"award-number":["16H06429, 16K21723, and 16H06434"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>The A(H1N1)pdm09 virus emerged in 2009 and continues to circulate in human populations. Recent A(H1N1)pdm09 viruses, that is, A(H1N1)pdm09 viruses circulating in the post-pandemic era, can cause more or less severe infections than those caused by the initial pandemic viruses. To evaluate the changes in pathogenicity of the A(H1N1)pdm09 viruses during their continued circulation in humans, we compared the nucleotide and amino acid sequences of ten A(H1N1)pdm09 viruses isolated in Japan between 2009 and 2015, and experimentally infected mice with each virus. The severity of infection caused by these Japanese isolates ranged from milder to more severe than that caused by the prototypic pandemic strain A\/California\/04\/2009 (CA04\/09); however, specific mutations responsible for their pathogenicity have not yet been identified.<\/jats:p>","DOI":"10.3390\/v12020155","type":"journal-article","created":{"date-parts":[[2020,1,29]],"date-time":"2020-01-29T10:51:07Z","timestamp":1580295067000},"page":"155","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Comparison of the Pathogenicity in Mice of A(H1N1)pdm09 Viruses Isolated between 2009 and 2015 in Japan"],"prefix":"10.3390","volume":"12","author":[{"given":"Hiromichi","family":"Mitake","sequence":"first","affiliation":[{"name":"Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Atsuhiro","family":"Yasuhara","sequence":"additional","affiliation":[{"name":"Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tiago J. 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