@MichaelSFuhrer Let's say sensitivity of a survey is 50% and independent of infection ordinal (there are some false positive too, ignored here). 50% of first infections will be picked up, but 50% of second infections will also report as first infections.
@MichaelSFuhrer 假设一项调查的敏感性为 50%，并且与感染顺序无关（也有一些误报，此处忽略）。 50% 的首次感染会被感染，但 50% 的二次感染也会报告为首次感染。