However, it's still unclear whether asymptomatic people contribute significantly to the transmission. Last comment on that I heard from CDC interview by WSJ: "

However, it's still unclear whether asymptomatic people contribute significantly to the transmission. Last comment on that I heard from CDC interview by WSJ: "patient becomes contagious either after symptoms appeared, or right before that (couple hours)". And using common sense, if a person doesn't cough or breathe hard with air droplets, then they must be way less contagious naturally.