Hmm, this seems like a pretty big deal, and should give us caution to not have confidence we are not spreading covid-19 just because we feel fine. Makes masks

Hmm, this seems like a pretty big deal, and should give us caution to not have confidence we are not spreading covid-19 just because we feel fine. Makes masks seem more key. "We estimated that 44% (95% confidence interval, 25–69%) of secondary cases were infected during the index cases’ presymptomatic stage" "Disease control measures should be adjusted to account for probable substantial presymptomatic transmission."