Evaluating the Ascertainment Bias of SARS-CoV-2 Using Spatial Backcalculation of Airport Screening Data in Japan.
4 affiliations
- 1School of Public Health, Graduate School of Medicine, Kyoto University, Yoshida Konoe Cho, Sakyo-ku, Kyoto 606-8501, Japan.
- 2Department of Epidemiology, Japan Institute for Health Security, 1-21-1 Toyama, Shinjuku-ku, Tokyo 162-8655, Japan.
- 3Center for Health Security, Graduate School of Medicine, Kyoto University, Yoshida Konoe Cho, Sakyo-ku, Kyoto 606-8501, Japan.
- 4Department of Epidemiology and Biostatistics, Schulich School of Medicine & Dentistry, Western University, 1465 Richmond Street, London, ON N6G 2M1, Canada.
Abstract
Background
Despite global efforts to strengthen surveillance systems, ascertainment bias persisted. We evaluated the extent of this bias by comparing Japan's airport entry screening data with local surveillance data.Methods
Entry screening data of non-Japanese passengers arriving from 25 countries were analyzed, and countries were categorized by income level: high-income countries (HICs), upper-middle-income countries (UMICs), and lower-middle-income countries (LMICs). A statistical model was developed to describe entry screening positivity using surveillance data of the country of origin.Results
Ascertainment bias was lowest in HICs (positivity = 1.76 times that of local surveillance data, 95% confidence interval [CI]: 1.42, 2.13). Bias estimates in the remaining income levels were substantially higher: positivity was 25.71 times (95% CI: 21.72, 30.09) and 24.38 times (95% CI: 21.29, 27.72) than that of surveillance data in UMICs and LMICs, respectively. The denial of new entry visas was associated with a relative risk reduction of 0.78 (95% CI: 0.72, 0.83) in UMICs. However, no significant effect was observed in LMICs (-0.13; 95% CI: -0.33, 0.03). Vaccination did not substantially alter post-arrival positivity.Conclusions
A comparison of entry screening data with local surveillance data indicated that ascertainment bias depends on income level.
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BibTeX
@article{liu2026evaluating,
title = {{Evaluating the Ascertainment Bias of SARS-CoV-2 Using Spatial Backcalculation of Airport Screening Data in Japan.}},
author = {Shiqi Liu and Asami Anzai and Hiroshi Nishiura},
journal = {Infectious disease reports},
year = {2026},
month = oct,
doi = {10.3390/idr18050117},
url = {https://europepmc.org/article/MED/42930508},
note = {CC BY},
}
RIS
TY - JOUR
TI - Evaluating the Ascertainment Bias of SARS-CoV-2 Using Spatial Backcalculation of Airport Screening Data in Japan.
AU - Shiqi Liu
AU - Asami Anzai
AU - Hiroshi Nishiura
PY - 2026
DA - 2026/10/09
JO - Infectious disease reports
DO - 10.3390/idr18050117
UR - https://europepmc.org/article/MED/42930508
AB - Background Despite global efforts to strengthen surveillance systems, ascertainment bias persisted. We evaluated the extent of this bias by comparing Japan's airport entry screening data with local surveillance data.Methods Entry screening data of non-Japanese passengers arriving from 25 countries were analyzed, and countries were categorized by income level: high-income countries (HICs), upper-middle-income countries (UMICs), and lower-middle-income countries (LMICs). A statistical model was developed to describe entry screening positivity using surveillance data of the country of origin.Results Ascertainment bias was lowest in HICs (positivity = 1.76 times that of local surveillance data, 95% confidence interval [CI]: 1.42, 2.13). Bias estimates in the remaining income levels were substantially higher: positivity was 25.71 times (95% CI: 21.72, 30.09) and 24.38 times (95% CI: 21.29, 27.72) than that of surveillance data in UMICs and LMICs, respectively. The denial of new entry visas was associated with a relative risk reduction of 0.78 (95% CI: 0.72, 0.83) in UMICs. However, no significant effect was observed in LMICs (-0.13; 95% CI: -0.33, 0.03). Vaccination did not substantially alter post-arrival positivity.Conclusions A comparison of entry screening data with local surveillance data indicated that ascertainment bias depends on income level.
SN - 2036-7430
SN - 2036-7449
ER -