Epidemic History and Iatrogenic Transmission of Blood-borne Viruses

1. Background

1.1 The emergence of HIV

The HIV/AIDS pandemic has so far caused about 29 million deaths, while 33 million individuals currently live with HIV. Even if this will have no direct impact on the future course of the epidemic, it is important to try to understand the factors that allowed the successful emergence of HIV-1, first as a moral obligation towards the victims, and then to draw lessons that could ultimately help mankind avoid facing similar threats in the future.

There is now no doubt that the source of HIV-1 group M (the strain causing the pandemic) is the Pan troglodytes troglodytes chimpanzee of central Africa. This primate inhabits south Cameroon, Gabon, Equatorial Guinea, the Congo Republic, the south-west of the Central African Republic (CAR), the Cabinda enclave and a small part of the Democratic Republic of Congo (DRC) (the Mayombe area north of the river). It is thought that the original cross-species transmission, from chimpanzee to man, occurred around the beginning of the 20th century, probably through the manipulation of chimpanzee meat by a hunter or a cook, so that the common ancestor of group M existed in humans around 1910-1920. It is extremely unlikely that this very first infected human lived in the DRC, where populations of Pan troglodytes troglodytes were very small. The virus then slowly disseminated along trading routes, eventually reaching Léopoldville and Brazzaville no later than 1959.

It is in this large bi-national conurbation that the virus managed to flourish and diversify, as supported by several findings:

1. The broadest genetic diversity of HIV-1 is found in Kinshasa and Brazzaville. All HIV-1 subtypes and many recombinants have been found there. Indeed, the genetic diversity of HIV-1 in Kinshasa in the mid-1980s, twenty-five years ago, was higher than that currently found in any other part of the world.
2. The two most ancient isolates of HIV-1 have been located in Kinshasa, one from a blood sample obtained in 1959 and the second from a lymph node biopsy obtained in 1960.
3. Testing of serum collections stored for years showed that among mothers bringing their children to an under-five clinic in the Lemba district of Kinshasa, HIV prevalence was 0.25% in 1970 and 3.0% in 1980.
4. HIV prevalence among the general adult population of Kinshasa and Brazzaville in the mid-1980s was already between 5 and 8%, while it was far lower in Yaoundé, Douala and Libreville, the other large cities of central Africa.
5. Several serologically proven cases of AIDS were diagnosed retrospectively among Belgian nationals who were probably infected in the Congo in the 1960s.