Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Yura K Ko; Yuki Furuse; Kota Ninomiya; Kanako Otani; Hiroki Akaba; Reiko Miyahara; Tadatsugu Imamura; Takeaki Imamura; Alex R Cook; Mayuko Saito; Motoi Suzuki; Hitoshi Oshitani

doi:10.1016/j.ijid.2022.01.036

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Int J Infect Dis. 2022 Mar:116:365-373. doi: 10.1016/j.ijid.2022.01.036. Epub 2022 Jan 20.

Authors

Yura K Ko¹, Yuki Furuse², Kota Ninomiya³, Kanako Otani⁴, Hiroki Akaba⁵, Reiko Miyahara⁶, Tadatsugu Imamura⁷, Takeaki Imamura⁸, Alex R Cook⁹, Mayuko Saito¹⁰, Motoi Suzuki¹¹, Hitoshi Oshitani¹²

Affiliations

¹ Center for Surveillance, Immunization, and Epidemiologic Research, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo, Japan; Department of Virology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, Japan 980-8575. Electronic address: [email protected].
² Institute for Frontier Life and Medical Sciences, Kyoto University, 53 kawaramachi, Shogoin, Sakyo-ku, Kyoto, Japan; Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki, Japan. Electronic address: [email protected].
³ Graduate School of Pharmaceutical Sciences, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; National Institute of Public Health, 2-3-6 Minami, Wako-shi, Saitama 351-0197 Japan. Electronic address: [email protected].
⁴ Center for Surveillance, Immunization, and Epidemiologic Research, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo, Japan. Electronic address: [email protected].
⁵ Department of Virology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, Japan 980-8575. Electronic address: [email protected].
⁶ Center for Surveillance, Immunization, and Epidemiologic Research, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo, Japan. Electronic address: [email protected].
⁷ Japan International Cooperation Agency, 5-25 Niban-cho, Chiyoda-ku, Tokyo 102-8012, Japan; Center for Postgraduate Education and Training, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, Japan. Electronic address: [email protected].
⁸ Department of Virology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, Japan 980-8575. Electronic address: [email protected].
⁹ Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, 12 Science Drive 2, #10-01, Singapore. Electronic address: [email protected].
¹⁰ Department of Virology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, Japan 980-8575. Electronic address: [email protected].
¹¹ Center for Surveillance, Immunization, and Epidemiologic Research, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo, Japan. Electronic address: [email protected].
¹² Department of Virology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, Japan 980-8575. Electronic address: [email protected].

Abstract

Objectives: Super-spreading events caused by overdispersed secondary transmission are crucial in the transmission of COVID-19. However, the exact level of overdispersion, demographics, and other factors associated with secondary transmission remain elusive. In this study, we aimed to elucidate the frequency and patterns of secondary transmission of SARS-CoV-2 in Japan.

Methods: We analyzed 16,471 cases between January 2020 and August 2020. We generated the number of secondary cases distribution and estimated the dispersion parameter (k) by fitting the negative binomial distribution in each phase. The frequencies of the secondary transmission were compared by demographic and clinical characteristics, calculating the odds ratio using logistic regression models.

Results: We observed that 76.7% of the primary cases did not generate secondary cases with an estimated dispersion parameter k of 0.23. The demographic patterns of primary-secondary cases differed between phases, with 20-69 years being the predominant age group. There were higher proportions of secondary transmissions among older individuals, symptomatic patients, and patients with 2 days or more between onset and confirmation.

Conclusions: The study showed the estimation of the frequency of secondary transmission of SARS-CoV-2 and the characteristics of people who generated the secondary transmission.

Keywords: COVID-19; Dispersion parameter; Overdispersion; Secondary transmission; Super-spreading events.

MeSH terms

COVID-19* / epidemiology
Demography
Humans
Japan / epidemiology
SARS-CoV-2*