AIDS has claimed more than 33 million lives and its causative agent, the human immunodeficiency virus (HIV), has thus far proved impossible to find a vaccine for.

Professor Dr Jacques Pepin, an epidemiologist at Université de Sherbrooke in Canada, has been trying to discover the origin of HIV for decades, since his time as a GP in Zaire (today the Democratic Republic of Congo) in the 1980s. Previous studies found the simian immunodeficiency virus (SIV) in chimps first crossed over into humans in South-East Cameroon at the start of the 20th century.

Simian immunodeficiency virus can be fatal to chimps and is exactly the same as HIV; the only difference between the two is the host it lives inside. HIV is an example of zoonotic transmission, where a pathogen can cross from one species to another, like COVID-19, bird flu, and cowpox.

In the acclaimed first edition of his book Origin of AIDS, published in 2011, Pepin concluded that HIV likely infected a hunter in Cameroon at the start of the 20th century, before spreading to Léopoldville, now known as Kinshasa in the Congo. Now, a revised version of this ‘cut hunter’ hypothesis has been published which states the original ‘Patient Zero’ was not a native hunter, but instead a starving World War I soldier forced to hunt chimps for food when stuck in the remote forest around Moloundou, Cameroon in 1916 – giving rise to the ‘cut soldier’ theory.

In an exclusive interview, Pepin reveals how colonialism helped create the ongoing AIDS epidemic. “During World War I, Germany had a number of colonies in Africa, and the Allied forces decided to invade these colonies, one of which was Cameroon,” said Pepin.

One of the invasion routes saw 1,600 soldiers venture from Léopoldville up the Congo River and its tributary, the Sanger River before reaching the final destination in Cameroon on foot. This path took them to the remote town on Moloundou, the location which previous studies had speculated was the site of the very first HIV infection.

The normal population of the entire South-East region of Cameroon in the 1920s was around 4,000, living off cassava, other crops and bushmeat. These people fled when the soldiers arrived due to their brutal reputation for slaughtering towns and ruthlessly raping women.

As a result, the soldiers soon ran out of food and were reliant on supplies sent by river from Brazzaville and Léopoldville. The logistical issues led to mass starvation and forced soldiers to venture into the forest to hunt for any animal that could be eaten.

“My hypothesis is that one of the soldiers got infected while hunting in the forest. A chimpanzee was killed and when cutting the animal to bring it back, there was an injury which got infected with the virus. Eventually, the soldier, after the war, came back all the way to Léopoldville and probably started the very first train of transmission in Léopoldville itself.”

Pepin believes that once the virus had this foothold in the human population, it initially spread slowly, confined to what was the then capital of the Belgian colony. He estimates that this one case of zoonotic transmission in 1916 led to around 500 infected people in the early 1950s.

– Agencies