Having identified the source of HIV-1, the next question is: when did the virus manage to cross species from chimps to humans? It has often been said that AIDS was a new disease on the African continent. Apart from the published cases mentioned in Chapter 1, clinicians working in central Africa, for instance Dr Bila Kapita, chief of internal medicine at Hôpital Mama Yemo in Kinshasa, reported that, at least since the mid-1970s, they started seeing cases that in retrospect were very likely to have been AIDS. This would be consistent with some degree of dissemination of the virus during the mid-1960s, given the average ten-year interval between infection and symptomatic disease. But could the disease have been present even earlier?

Bush medicine

In most district or regional hospitals of countries inhabited by P.t. troglodytes, the diagnostic facilities during the colonial era (and even now) were so minimal that it would have been difficult, even for astute and experienced clinicians, to recognise the emergence of a new disease characterised by intermittent fevers and profound wasting. Most such institutions did not have any kind of half-decent microbiology laboratory. No cultures were done, either for common bacterial pathogens or the agent of tuberculosis, and diagnoses were based on stains made directly on the specimens, or solely on the combination of symptoms and signs found during the clinical examination. Fifty years later, I found the same situation at the Nioki hospital in Zaire: nothing had changed. This approach was relatively effective for diagnosing parasitic diseases (malaria, sleeping sickness, filariasis, intestinal parasites) but very insensitive for most bacterial diseases. Little radiological investigation was available either; only in the best hospitals was it possible to get something as elementary as a chest x-ray. The first x-ray machine in Brazzaville was installed in 1931, two years before one became available in Léopoldville.