A lot of comment on the number and severity of cases being detected now compared to the peak of the pandemic; the commentary is underestimating both the effectiveness of surveillance in April, and the seriousness of the situation now. 1/13

We were doing 3000 - 4000 tests per day (not 500) in April, with positivity rates over 20%. We saw close to 1,000 case per day at peak. Seroprevalence studies suggest that for each detected case, there were 2 asymptomatic or mild cases not detected. 2/13

This is highly effective surveillance by international standards, all the more remarkable given the speed with which it was mobilized and the historic underinvestment in such systems. 3/13

If we had 3,000 new infections per day at peak, at an average infectious period of 7 days, that’s 21,000 active infections (not 50,000). 4/13