You get on Google, you Google, and you find, actually the only people tested in Burkina Faso in 1991 are STD patients and pregnant women, which is not a terribly representative group of people.
你上了谷歌 却发现 在布基纳法索1991年受测试的人 只有性病患者和孕妇 这并不是极具代表性的一个人群