>[!abstract] >[[Korber et al., 2000|Korber et al. (2000)]] estimated the date of a chimpanzee-to-human transmission event (assuming a simian origin) of HIV-1 to be 1931 (95% confidence interval 1915–1941). > >[[Zhu et al., 1998]] identified HIV-1 in a plasma sample (ZR59) taken in 1959 from an adult Bantu male in Léopoldville, Belgian Congo (now Kinshasa, Democratic Republic of Congo). This is the oldest known human sample of HIV-1. > >[[Worobey et al., 2008]] showed sizable genetic distance between ZR59 and another sample (DRC60) taken from an adult female in 1960, also in Léopoldville, directly demonstrating that the virus was already diversified in Central-West Africa at that time, and that ZR59 was unlikely to be patient zero, whose identity remains unknown. >[!related] >- **North** (upstream): — >- **West** (similar): — >- **East** (different): — >- **South** (downstream): —