It has been mentioned in a number of threads that there are likely a significant number of underreported cases, e.g. John Hopkins study. However, if cases are u

It has been mentioned in a number of threads that there are likely a significant number of underreported cases, e.g. John Hopkins study. However, if cases are underreported and it is implied that these are more mild cases, would that mean that these more mild cases are less likely to infect others? I ask this because if there's a hidden but significant fraction of cases, it seems to be beyond the scope of nearly every quarantine (i.e. asymptomatic people going about their day) and if the transmission rate is equal I would think we would see a lot of uncontrolled spreading. Perhaps Italy and South Korea are an example of this, although I would've imagined far more Western countries with deep distributed infections if are so many high transmission, light or asymptomatic carriers around. Concurrent to this, I am surprised the original dozen set of infections in the US seemed to have not infected nearly anyone else, assuming close contacts were appropriately monitored.