The first eleven cases of SARS-CoV-2 Omicron variant infection in Japan: A focus on viral dynamics

Nobumasa Okumura; Shinya Tsuzuki; Sho Saito; Tomoya Saito; Satoshi Takasago; Masayuki Hojo; Noriko Iwamoto; Norio Ohmagari

doi:10.35772/ghm.2021.01124

The first eleven cases of SARS-CoV-2 Omicron variant infection in Japan: A focus on viral dynamics

Glob Health Med. 2022 Apr 30;4(2):133-136. doi: 10.35772/ghm.2021.01124.

Authors

Nobumasa Okumura¹, Shinya Tsuzuki^{1

2

3}, Sho Saito¹, Tomoya Saito⁴, Satoshi Takasago⁵, Masayuki Hojo⁶, Noriko Iwamoto¹, Norio Ohmagari^{1

2}

Affiliations

¹ Disease Control and Prevention Center, National Center for Global Health and Medicine, Tokyo, Japan.
² AMR Clinical Reference Center, National Center for Global Health and Medicine, Tokyo, Japan.
³ Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.
⁴ Center for Emergency Preparedness and Response, National Institute of Infectious Diseases, Tokyo, Japan.
⁵ Department of Pediatrics, National Center for Global Health and Medicine, Tokyo, Japan.
⁶ Department of Respiratory Medicine, National Center for Global Health and Medicine, Tokyo, Japan.

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has spread rapidly worldwide. We report the clinical characteristics and threshold cycle (Ct) values of the first 11 patients infected with the SARS-CoV-2 Omicron variant in Japan. All patients were younger returnees from abroad; 10 patients had received two doses of vaccine. Estimated Ct values for the 11 patients were 6.0 (95% confidence interval [CI] 4.2-7.3) days for > 30, 10.6 (95% CI 9.5-11.9) days for > 35, 15.1 (95% CI 13.6-17.6) days for > 40, and 19.7 (95% CI 17.3- 23.7) days for > 45. Our results provide important insights for indicators of infection control.

Keywords: B.1.1.529; COVID-19; characteristics; threshold cycle.

2022, National Center for Global Health and Medicine.