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

ABSTRACT: Objsectives: Super-spreading events caused by overdispersed secondary transmission is crucial in the transmission of coronavirus disease 2019 (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 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 by 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 cases among elderly, symptomatic cases, and those with two days or more between onset and confirmation.

Conclusions

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

SUBMITTER: Ko YK 

PROVIDER: S-EPMC8772065 | biostudies-literature |

REPOSITORIES: biostudies-literature