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Exploring secondary SARS-CoV-2 transmission from asymptomatic cases using contact tracing data
Ko Nakajo1,2, Hiroshi Nishiura3,4
1Graduate, School of Medicine, Hokkaido University, Kita 15 Jo Nishi 7 Chome, Kita-ku, Sapporo-shi, Hokkaido, 060-8638, Japan.
Theoretical Biology & Medical Modelling
|July 17, 2021
Summary
Asymptomatic severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections have low transmissibility (0.22), suggesting contract tracing should focus on symptomatic cases to manage coronavirus disease 2019 (COVID-19) effectively.
Area of Science:
- Epidemiology
- Virology
- Public Health
Background:
- Asymptomatic severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections pose a public health challenge due to silent viral propagation.
- Understanding transmission dynamics of asymptomatic coronavirus disease 2019 (COVID-19) is crucial for effective pandemic control.
Purpose of the Study:
- To investigate SARS-CoV-2 transmissibility among young asymptomatic individuals.
- To determine if symptomatology influences the transmission of symptomatic versus asymptomatic infections.
Main Methods:
- Analysis of an early SARS-CoV-2 transmission cluster among university students in Japan.
- Application of discrete and two-type branching process models to estimate reproduction numbers.
- Estimation of the proportion of secondary symptomatic cases from primary symptomatic and asymptomatic cases.
Main Results:
- The reproduction number for symptomatic cases was 1.14 (95% CI: 0.61-2.09).
- The relative reproduction number for asymptomatic cases was estimated at 0.19 (95% CI: 0.03-0.66), indicating limited transmission.
- No significant tendency for symptomatic cases to produce predominantly symptomatic secondary infections was observed.
Conclusions:
- Asymptomatic SARS-CoV-2 infections exhibit significantly lower transmissibility (estimated relative reproduction number of 0.22) compared to symptomatic infections.
- Findings support prioritizing contract tracing efforts on symptomatic individuals, especially with limited testing resources, for efficient COVID-19 control.
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