Skip to content
DraconiticResearch
Search Sources API
201,642 studies31 sourcesUpdated 11 min ago
Peer-reviewedCC BY 4.0Frontiers in Public Health

Estimating the effective reproduction number of HIV infections in Japan from 1985 to 2025: a Bayesian extended back calculation

  • Seiko Fujiwara1,2
  • Hiroshi Nishiura1,2,3
  1. 1Department of Epidemic Intelligence and Health Emergency Response, Center for Health Security, Graduate School of Medicine, Kyoto University
  2. 2School of Public Health, Graduate School of Medicine, Kyoto University
  3. 3Department of Epidemiology and Biostatistics, Schulich School of Medicine & Dentistry, Western University
Open at sourcePDFDOICite

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.

Methods: 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.

Results: 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.

Conclusion: 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.

Related

  1. Bayesian Anchored Latent Learning for Estimating State Trajectories
    J. B. Gibbons, N. Leenaerts, A. D. Mandavia +11
    medRxivPreprintAll rights reservedFull textEpidemiology & public healthmedRxiv
  2. Time to sustained control of the effective reproduction number as a failure-time estimand: a county-level analysis of the first SARS-CoV-2 wave in the United States.
    A. Kakasis, M. Panagiotidou, N. Demiris +2
    medRxivPreprintCC BY-NC-NDFull textEpidemiology & public healthmedRxiv
  3. Estimating duration in sex work from cross-sectional studies: a Bayesian global synthesis suggests shorter durations
    J. Knight, S. Wang, L. Wang +1
    medRxivPreprintCC BYFull textEpidemiology & public healthmedRxiv
  4. Estimating cumulative incidence from partially missing time series of respiratory viral infections
    Sudhir Venkatesan, Lisa White, Hyewon Nina Koo +6
    PLOS OnePeer-reviewedCC BY 4.0Full textEpidemiology & public healthPLOS
  5. Enhanced infection control measures during the COVID-19 pandemic significantly reduced healthcare-associated infections in a Chinese cancer hospital: a Bayesian structural time series analysis
    Qingqing Tian, Qin Huang, Hui Wang +5
    Frontiers in Public HealthPeer-reviewedCC BY 4.0Epidemiology & public healthFrontiersCrossref

Cite

BibTeXRIS
BibTeX
@article{fujiwara2026estimating,
  title = {{Estimating the effective reproduction number of HIV infections in Japan from 1985 to 2025: a Bayesian extended back calculation}},
  author = {Seiko Fujiwara and Hiroshi Nishiura},
  journal = {Frontiers in Public Health},
  year = {2026},
  month = oct,
  doi = {10.3389/fpubh.2026.1944492},
  url = {https://www.frontiersin.org/articles/10.3389/fpubh.2026.1944492/full},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Estimating the effective reproduction number of HIV infections in Japan from 1985 to 2025: a Bayesian extended back calculation
AU  - Seiko Fujiwara
AU  - Hiroshi Nishiura
PY  - 2026
DA  - 2026/10/27
JO  - Frontiers in Public Health
DO  - 10.3389/fpubh.2026.1944492
UR  - https://www.frontiersin.org/articles/10.3389/fpubh.2026.1944492/full
AB  - 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.  Methods: 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.  Results: 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.  Conclusion: 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.
SN  - 2296-2565
ER  -