Note the caveat here: "the initial approach to testing was to identify patients among those with travel histories or persons with more severe disease, and these

Note the caveat here: "the initial approach to testing was to identify patients among those with travel histories or persons with more severe disease, and these data might overestimate the prevalence of severe disease". One of the things that makes it frustratingly hard to tell the real likelihoods is that almost all data has this problem to some extent, except maybe the Diamond Princess cases, and there weren't enough young people on there to get good numbers.