Tohoku J. Exp. Med., 2022 October, 258(2)

COVID-19-Related Symptoms during the SARS-CoV-2 Omicron (B.1.1.529) Variant Surge in Japan

Tetsuya Akaishi,¹ Shigeki Kushimoto,² Yukio Katori,³ Noriko Sugawara,⁴ Hiroshi Egusa,⁵ Kaoru Igarashi,⁶ Motoo Fujita,⁷ Shigeo Kure,⁴ Shin Takayama,¹ Michiaki Abe,¹ Akiko Kikuchi,¹ Minoru Ohsawa,¹ Kota Ishizawa,¹ Yoshiko Abe,¹ Hiroyuki Imai,⁸ Yohei Inaba,⁹ Yoko Iwamatsu-Kobayashi,¹⁰ Takashi Nishioka,¹¹ Ko Onodera¹ and Tadashi Ishii¹

¹Department of Education and Support for Regional Medicine, Tohoku University Hospital, Sendai, Miyagi, Japan
²Division of Emergency and Critical Care Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
³Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
⁴Department of Pediatrics, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
⁵Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
⁶Division of Craniofacial Anomalies, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
⁷Department of Emergency and Critical Care Medicine, Tohoku University Hospital, Sendai, Miyagi, Japan
⁸Clinical Skills Laboratory, Tohoku University School of Medicine, Sendai, Miyagi, Japan
⁹Course of Radiological Technology, Health Sciences, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
¹⁰Department of Dental Infection Control, Tohoku University Hospital, Sendai, Miyagi, Japan
¹¹Liaison Center for Innovative Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan

The exact profiles of the clinical symptoms related to the SARS-CoV-2 Omicron variant (B.1.1.529) remain largely uncertain. Therefore, this study aimed to clarify the clinical manifestations of infection with this variant. We enrolled individuals who were tested by quantitative nasopharyngeal swab reverse transcription-polymerase chain reaction (RT-PCR) test at a large screening center in a city of Japan during the B.1.1.529 Omicron variant wave between January and May 2022, after contact with COVID-19 patients. Swab tests were planned to be performed approximately 4-5 days after contact. The presence of COVID-19-related symptoms was assessed at the swab test site. Among the 2,507 enrolled individuals, 943 (37.6%) were RT-PCR test-positive and 1,564 (62.4%) were test-negative. Among the 943 PCR test-positive participants, the prevalence of the symptoms was as follows: 47.3% with cough, 32.9% with sore throat, 18.4% with fatigability, 12.7% with fever of ≥ 37.5℃, 9.9% with dyspnea, 2.1% with dysosmia, and 1.4% with dysgeusia. The prevalence of cough, sore throat, dyspnea, and fatigability was higher among adults aged ≥ 18 years than among children and adolescents. The prevalence of dysosmia and dysgeusia remarkably decreased during the Omicron wave (1-3%) compared to during the pre-Omicron variant waves (15-25%). In summary, common COVID-19-related symptoms during the Omicron variant wave included cough and sore throat, followed by fatigability, fever, and dyspnea. The prevalence of most of these symptoms was higher in adults than in non-adults. The prevalence of dysosmia and dysgeusia remarkably decreased with the Omicron variant than with pre-Omicron variants.

Keywords —— coronavirus disease 2019 (COVID-19); Omicron variant (B.1.1.529); severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); sore throat; symptoms

© 2022 Tohoku University Medical Press

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Tohoku J. Exp. Med 2022, 258, 103-110.

Correspondence: Tetsuya Akaishi, Department of Education and Support for Regional Medicine, Tohoku University, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.

e-mail: t-akaishi@med.tohoku.ac.jp