Reconstructing the history of HIV

1In the early 1980s, when the world discovered HIV, several million people were already infected. This immediately raised the question of the origin of the epidemic and virus. A US primate research centre identified a variant in a macaque monkey in 1983. Shortly afterwards, the blood of a large number of monkeys in captivity was analysed, confirming the presence of HIV cousins in 40-odd primate species. In 1987 however, researchers made an even more crucial discovery when they identified a virus very similar to the one responsible for the global pandemic in a chimpanzee in captivity in Gabon.

Child’s drawing, Senegal.

••• Researchers identified the origin of the AIDS virus in great apes in Cameroon •••

2To claim that HIV comes from monkeys however, one should go further and study wild chimpanzees. The problem is these populations are protected and cannot be caught, which makes research more difficult. As they could not access their blood, researchers studied their droppings. In 2002, having verified in the laboratory that the faeces of infected chimpanzees contained viral fragments, researchers began collecting thousands of wild chimpanzee and gorilla droppings in Central Africa.

Female gorilla, Southern Cameroon.

3The results initially revealed a contrasted epidemiological situation: certain populations were not infected: while in others 30% to 50% of individuals were contaminated. More importantly, primate colonies were infected with viruses from the same family but all were specific to the region where they lived. These studies also showed that gorillas from Cameroon were infected with a virus similar to HIV-1.

4This made it possible to map the four starting points of the four types of HIV-1 virus (M, N, O, P) and the animal-to-human transmission points. They all came from Cameroon: for types O and P, gorillas from the Central South and West, respectively; for types N and M, chimpanzees in the Central South and East, in the Lobéké region. The HIV-1 M virus, the most widespread, was responsible for the pandemic, whereas the others remained endemic in Cameroon.

“These analysis methods based on wildlife droppings helped identify the origin of other pathogens, and will facilitate the in-depth study of pathogens on the level of the human-wildlife interface, to shed light on the emergence of certain infectious diseases.” 
Eitel Mpoudi Ngole, director of the Research Centre for Emerging and Re-emerging Diseases (CREMER), Yaoundé, Cameroon