@article{oai:nagasaki-u.repo.nii.ac.jp:00028126,
 author = {Han, Su Myat and Robert, Alexis and Masuda, Shingo and Yasaka, Takahiro and Kanda, Satoshi and Komori, Kazuhiri and Saito, Nobuo and Suzuki, Motoi and Endo, Akira and Baguelin, Marc and Ariyoshi, Koya},
 issue = {1},
 journal = {Scientific Reports},
 month = {Apr},
 note = {Seasonal infuenza outbreaks remain an important public health concern, causing large numbers of hospitalizations and deaths among high-risk groups. Understanding the dynamics of individual transmission is crucial to design efective control measures and ultimately reduce the burden caused by infuenza outbreaks. In this study, we analyzed surveillance data from Kamigoto Island, Japan, a semi-isolated island population, to identify the drivers of infuenza transmission during outbreaks. We used rapid infuenza diagnostic test (RDT)-confrmed surveillance data from Kamigoto island, Japan and estimated age-specifc infuenza relative illness ratios (RIRs) over eight epidemic seasons (2010/11 to 2017/18). We reconstructed the probabilistic transmission trees (i.e., a network of who-infectedwhom) using Bayesian inference with Markov-chain Monte Carlo method and then performed a negative binomial regression on the inferred transmission trees to identify the factors associated with onwards transmission risk. Pre-school and school-aged children were most at risk of getting infected with infuenza, with RIRs values consistently above one. The maximal RIR values were 5.99 (95% CI 5.23, 6.78) in the 7–12 aged-group and 5.68 (95%CI 4.59, 6.99) in the 4–6 aged-group in 2011/12. The transmission tree reconstruction suggested that the number of imported cases were consistently higher in the most populated and busy districts (Tainoura-go and Arikawa-go) ranged from 10–20 to 30–36 imported cases per season. The number of secondary cases generated by each case were also higher in these districts, which had the highest individual reproduction number (Ref: 1.2–1.7) across the seasons. Across all inferred transmission trees, the regression analysis showed that cases reported in districts with lower local vaccination coverage (incidence rate ratio IRR= 1.45 (95% CI 1.02, 2.05)) or higher number of inhabitants (IRR= 2.00 (95% CI 1.89, 2.12)) caused more secondary transmissions. Being younger than 18 years old (IRR= 1.38 (95%CI 1.21, 1.57) among 4–6 years old and 1.45 (95% CI 1.33, 1.59) 7–12 years old) and infection with infuenza type A (type B IRR= 0.83 (95% CI 0.77, 0.90)) were also associated with higher numbers of onwards transmissions. However, conditional on being infected, we did not fnd any association between individual vaccination status and onwards transmissibility. Our study showed the importance of focusing public health eforts on achieving high vaccine coverage throughout the island, especially in more populated districts. The strong association between local vaccine coverage (including neighboring regions), and the risk of transmission indicate the importance of achieving homogeneously high vaccine coverage. The individual vaccine status may not prevent onwards transmission, though it may reduce the severity of infection., Scientific reports, 13(1), art. no. 5393; 2023},
 title = {Transmission dynamics of seasonal influenza in a remote island population},
 volume = {13},
 year = {2023}
}