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Article

Increased Transmissibility of the SARS-CoV-2 Alpha Variant in a Japanese Population

1
Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan
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Department of Public Health and Medical Affairs, Osaka Prefectural Government, Osaka 540-8507, Japan
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Ibaraki Public Health Center of Osaka Prefectural Government, Ibaraki 567-8585, Japan
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Hirakata City of Public Health Center, Hirakata 573-8666, Japan
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Ehime Prefectural Institute of Public Health and Environmental Science, Matsuyama 790-0003, Japan
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College of Nursing, Aichi Medical University, Nagakute 480-1195, Japan
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Itako Public Health Center of Ibaraki Prefectural Government, Itako 311-2422, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: Paul B. Tchounwou
Int. J. Environ. Res. Public Health 2021, 18(15), 7752; https://doi.org/10.3390/ijerph18157752
Received: 30 June 2021 / Revised: 16 July 2021 / Accepted: 18 July 2021 / Published: 22 July 2021
(This article belongs to the Section Infectious Disease Epidemiology)
To assess the relative transmissibility of the SARS-CoV-2 Alpha variant compared to the pre-existing SARS-CoV-2 in Japan, we performed a cross-sectional study to determine the secondary attack rate of COVID-19 in household contacts before and after the Alpha variant became dominant in Osaka. We accessed 290 household contacts whose index cases were diagnosed between 1 and 20 December 2020 (the third epidemic group), at a time when Osaka was free of the Alpha variant. We also accessed 398 household contacts whose index cases were diagnosed between 20 April and 3 May 2021 (the fourth epidemic group), by which time the Alpha variant had become dominant. We identified 124 household contacts whose index case was determined positive for the Alpha variant (Alpha group) in this fourth group. The secondary attack rates in the fourth group (34.7%) and the Alpha group (38.7%) were significantly higher than that in the third group (19.3%, p < 0.001). Multivariable Poisson regression analysis with a robust error variance showed a significant excess risk in the fourth group (1.90, 95% CI = 1.47–2.48) and the Alpha group (2.34, 95% CI = 1.71–3.21). This finding indicates that the SARS-CoV-2 Alpha variant has an approximately 1.9–2.3-fold higher transmissibility than the pre-existing virus in the Japanese population. View Full-Text
Keywords: SARS-CoV-2; Alpha variant; N501Y; transmissibility; household contact; Japanese SARS-CoV-2; Alpha variant; N501Y; transmissibility; household contact; Japanese
MDPI and ACS Style

Tanaka, H.; Hirayama, A.; Nagai, H.; Shirai, C.; Takahashi, Y.; Shinomiya, H.; Taniguchi, C.; Ogata, T. Increased Transmissibility of the SARS-CoV-2 Alpha Variant in a Japanese Population. Int. J. Environ. Res. Public Health 2021, 18, 7752. https://doi.org/10.3390/ijerph18157752

AMA Style

Tanaka H, Hirayama A, Nagai H, Shirai C, Takahashi Y, Shinomiya H, Taniguchi C, Ogata T. Increased Transmissibility of the SARS-CoV-2 Alpha Variant in a Japanese Population. International Journal of Environmental Research and Public Health. 2021; 18(15):7752. https://doi.org/10.3390/ijerph18157752

Chicago/Turabian Style

Tanaka, Hideo, Atsushi Hirayama, Hitomi Nagai, Chika Shirai, Yuki Takahashi, Hiroto Shinomiya, Chie Taniguchi, and Tsuyoshi Ogata. 2021. "Increased Transmissibility of the SARS-CoV-2 Alpha Variant in a Japanese Population" International Journal of Environmental Research and Public Health 18, no. 15: 7752. https://doi.org/10.3390/ijerph18157752

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