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Article

Shorter Incubation Period among COVID-19 Cases with the BA.1 Omicron Variant

1
Public Health Center of Neyagawa City, Neyagawa 572-0838, Japan
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Itako Public Health Center of Ibaraki Prefectural Government, Itako 311-2422, Japan
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Public Health Center of Suita City, Suita 564-0072, Japan
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Ibaraki Public Health Center of Osaka Prefectural Government, Ibaraki 567-8585, Japan
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Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan
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Ibaraki Prefetural Office, Mito 310-0852, Japan
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College of Nursing, Aichi Medical University, Nagakute 480-1195, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: Paul B. Tchounwou
Int. J. Environ. Res. Public Health 2022, 19(10), 6330; https://doi.org/10.3390/ijerph19106330
Received: 25 April 2022 / Revised: 20 May 2022 / Accepted: 22 May 2022 / Published: 23 May 2022
(This article belongs to the Special Issue Epidemiology and Public Healthcare Systems during COVID-19)
We aimed to elucidate the range of the incubation period in patients infected with the SARS-CoV-2 Omicron variant in comparison with the Alpha variant. Contact tracing data from three Japanese public health centers (total residents, 1.06 million) collected following the guidelines of the Infectious Diseases Control Law were reviewed for 1589 PCR-confirmed COVID-19 cases diagnosed in January 2022. We identified 77 eligible symptomatic patients for whom the date and setting of transmission were known, in the absence of any other probable routes of transmission. The observed incubation period was 3.03 ± 1.35 days (mean ± SDM). In the log-normal distribution, 5th, 50th and 95th percentile values were 1.3 days (95% CI: 1.0–1.6), 2.8 days (2.5–3.1) and 5.8 days (4.8–7.5), significantly shorter than among the 51 patients with the Alpha variant diagnosed in April and May in 2021 (4.94 days ± 2.19, 2.1 days (1.5–2.7), 4.5 days (4.0–5.1) and 9.6 days (7.4–13.0), p < 0.001). As this incubation period, mainly of sublineage BA.1, is even shorter than that in the Delta variant, it is thought to partially explain the variant replacement occurring in late 2021 to early 2022 in many countries. View Full-Text
Keywords: SARS-CoV-2; COVID-19; Omicron variant; incubation period; Alpha variant; Japanese Public Health Center; contact tracing SARS-CoV-2; COVID-19; Omicron variant; incubation period; Alpha variant; Japanese Public Health Center; contact tracing
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MDPI and ACS Style

Tanaka, H.; Ogata, T.; Shibata, T.; Nagai, H.; Takahashi, Y.; Kinoshita, M.; Matsubayashi, K.; Hattori, S.; Taniguchi, C. Shorter Incubation Period among COVID-19 Cases with the BA.1 Omicron Variant. Int. J. Environ. Res. Public Health 2022, 19, 6330. https://doi.org/10.3390/ijerph19106330

AMA Style

Tanaka H, Ogata T, Shibata T, Nagai H, Takahashi Y, Kinoshita M, Matsubayashi K, Hattori S, Taniguchi C. Shorter Incubation Period among COVID-19 Cases with the BA.1 Omicron Variant. International Journal of Environmental Research and Public Health. 2022; 19(10):6330. https://doi.org/10.3390/ijerph19106330

Chicago/Turabian Style

Tanaka, Hideo, Tsuyoshi Ogata, Toshiyuki Shibata, Hitomi Nagai, Yuki Takahashi, Masaru Kinoshita, Keisuke Matsubayashi, Sanae Hattori, and Chie Taniguchi. 2022. "Shorter Incubation Period among COVID-19 Cases with the BA.1 Omicron Variant" International Journal of Environmental Research and Public Health 19, no. 10: 6330. https://doi.org/10.3390/ijerph19106330

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