{
  "abstract": "Background: HIV transmission among men having sex with men remains a concerning issue in Japan. Therefore, the purpose of the present study was to estimate the effective reproduction number R ( t ) of HIV by coupling a renewal process model with an existing extended back-calculation model in a Bayesian framework.\n\nMethods: We analyzed the annual number of HIV diagnoses and AIDS cases among Japanese males from 1985 through 2025. Using a Bayesian back-calculation with penalized B -splines for the incidence and the diagnosis rate of HIV with a renewal equation, we estimated R ( t ) for Japan and different geographic regions within the country.\n\nResults: From 2008 to 2010, we observed a consistent median value of R ( t ) < 1, with the most recent estimate of R ( t ) being the most uncertain. R ( t ) < 1 was apparent in major metropolitan areas, including Tokyo, Kanto–Koshinetsu, and Kinki, where even the upper bound of the 95% credible interval fell below 1 in the early-to-mid 2010s. The annual HIV diagnosis rate declined from shortly before the start of the COVID-19 pandemic, and the estimated proportion of HIV-infected individuals has increased only slowly in recent years, with the proportion of diagnosed individuals not reaching 95% or even 90% of the true total.\n\nConclusion: Our general R ( t ) value indicates that the control of HIV/AIDS in Japan has been successful over the long term, including during the COVID-19 pandemic. However, the uncertainty of recent R ( t ) values suggests the need for regular updates of the estimate; reforming the testing and treatment strategies in Japan is vital to accomplishing this goal.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Epidemic Intelligence and Health Emergency Response, Center for Health Security, Graduate School of Medicine, Kyoto University",
    "School of Public Health, Graduate School of Medicine, Kyoto University",
    "Department of Epidemiology and Biostatistics, Schulich School of Medicine & Dentistry, Western University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Seiko Fujiwara"
    },
    {
      "affs": [
        0,
        1,
        2
      ],
      "name": "Hiroshi Nishiura"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/62qpczw412q0w.bib",
  "cited_by": 0,
  "doi": "10.3389/fpubh.2026.1944492",
  "fulltext_url": null,
  "id": "62qpczw412q0w",
  "issns": [
    "2296-2565"
  ],
  "landing_url": "https://www.frontiersin.org/articles/10.3389/fpubh.2026.1944492/full",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2725|HIV/AIDS Research and Interventions"
    ]
  ],
  "openalex": "W7223867635",
  "pdf_url": "https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2026.1944492/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": "Frontiers Media SA",
  "ris": "https://research.draconitic.com/paper/62qpczw412q0w.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:24Z",
      "native_id": "10.3389/fpubh.2026.1944492",
      "source": "crossref",
      "url": "https://www.frontiersin.org/articles/10.3389/fpubh.2026.1944492/full"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:2725|HIV/AIDS Research and Interventions",
      "subfield": "infectious-disease"
    }
  ],
  "title": "Estimating the effective reproduction number of HIV infections in Japan from 1985 to 2025: a Bayesian extended back calculation",
  "title_text": "Estimating the effective reproduction number of HIV infections in Japan from 1985 to 2025: a Bayesian extended back calculation",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:20:24Z",
  "url": "https://research.draconitic.com/paper/62qpczw412q0w",
  "venue": "Frontiers in Public Health",
  "versions": []
}