From your link: What is the role of asymptomatic people in spreading the virus? Symptomatic people are not the only way the virus is shed. We know that at least 44% of all infections--and the majority of community-acquired transmissions--occur from people without any symptoms (asymptomatic or pre-symptomatic people). You can be shedding the virus into the environment for up to 5 days before symptoms begin. Infectious people come in all ages, and they all shed different amounts of virus. The figure below shows that no matter your age (x-axis), you can have a little bit of virus or a lot of virus (y-axis). (ref) https://www.erinbromage.com/post/the-risks-know-them-avoid-them Following the link at 44% to its source, which indicates it is inferred, not hard science: Abstract We report temporal patterns of viral shedding in 94 patients with laboratory-confirmed COVID-19 and modeled COVID-19 infectiousness profiles from a separate sample of 77 infector–infectee transmission pairs. We observed the highest viral load in throat swabs at the time of symptom onset, and inferred that infectiousness peaked on or before symptom onset. We estimated that 44% (95% confidence interval, 25–69%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home. Disease control measures should be adjusted to account for probable substantial presymptomatic transmission. https://www.nature.com/articles/s41591-020-0869-5