“In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak.”

Gao, Ming et al. A study on infectivity of asymptomatic SARS-CoV-2 carriers. Respiratory medicine vol. 169 (2020): 106026. https://doi.org/10.1016/j.rmed.2020.106026.