> People are thought to be most contagious when they are most symptomatic (the sickest).
Some spread might be possible before people show symptoms; there have been reports of this occurring with this new coronavirus, but this is not thought to be the main way the virus spreads.
> Although the possibility of transmission from an asymptomatic person has been reported （https://www.nejm.org/doi/full/10.1056/NEJMc2001468）, little is known on how Coronavirus disease 2019 (COVID-19) spreads from person to person. Generally speaking, with most respiratory viruses, people are thought to be most contagious when they are most symptomatic. https://www.cdc.gov/coronavirus/2019-ncov/about/transmission...
That CDC link [2] states that:
> People are thought to be most contagious when they are most symptomatic (the sickest). Some spread might be possible before people show symptoms; there have been reports of this occurring with this new coronavirus, but this is not thought to be the main way the virus spreads.
[1] https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryo...
[2] https://www.cdc.gov/coronavirus/2019-ncov/about/transmission...