Ex Africa semper aliquid novi

Out of Africa, there is always something new, wrote historian Pliny the Elder more than 2,000 years ago. He was quite right. As early as 1984, just three years after the first description of the new disease, it was suspected that HIV, its recently discovered aetiological agent (then known as human T-cell lymphotropic virus (HTLV)-III in the US, LAV (lymphadenopathy-associated virus) in Europe), originated in central Africa. This was mainly because the first studies in Africa, conducted in Zaire and Rwanda, showed that AIDS was common in Kinshasa and Kigali, where nearly 90% of sex workers were infected. These field studies were prompted by the observation that of the first few hundred cases of AIDS diagnosed in Europe, about half occurred among patients coming from central Africa, mostly from Zaire. Over the following years, the epidemiology of HIV-1 infection in Kinshasa would be described in great detail by a group of American, Belgian and Congolese researchers known as Projet Sida, based at Hôpital Mama Yemo (Mama Yemo was dictator Mobutu’s mother, a former sex worker, and she suffered the same fate as the Belgian colonists after her son was overthrown: this institution is now called Hôpital Général de Kinshasa). Projet Sida came to an abrupt end in 1991, when the whole of Kinshasa was looted by the city’s poor people. During the same period and until the 1994 genocide, similar epidemiological work was conducted in Kigali, 1,500 kilometres east of Kinshasa.

In retrospect, this early vision of central Africa as the source of HIV-1 was rather naive. Researchers assumed that since this was at the time the region with the highest prevalence (i.e. the proportion of the population that is infected) among groups representative of the general adult population, the virus must have originated there. There were at least two problems with this assumption.