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

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...

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Bibliographic Details
Published in:International journal of environmental research and public health 2022-05, Vol.19 (10), p.6330
Main Authors: Tanaka, Hideo, Ogata, Tsuyoshi, Shibata, Toshiyuki, Nagai, Hitomi, Takahashi, Yuki, Kinoshita, Masaru, Matsubayashi, Keisuke, Hattori, Sanae, Taniguchi, Chie
Format: Article
Language:English
Subjects:
Confidence intervals
Contact Tracing
Coronaviruses
COVID-19
COVID-19 - epidemiology
COVID-19 vaccines
Disease transmission
Humans
Immunization
Infections
Infectious Disease Incubation Period
Infectious diseases
Japan - epidemiology
Mutation
Normal distribution
Public health
SARS-CoV-2 - genetics
SARS-CoV-2 - physiology
Severe acute respiratory syndrome coronavirus 2
Viral infections
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Summary: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.
ISSN:1660-4601
1661-7827
1660-4601
DOI:10.3390/ijerph19106330