Geographic origin of AIDS pandemic identified

Scientists may have cracked the enigma of where, when and how the world's first AIDS pandemic originated. A study published in Science reveals the source of AIDS and how it spread.

AIDS is hailed as one of the most devastating diseases in the history of humanity.

Human immunodeficiency virus (HIV) is a virus spread through body fluids that affects specific cells of the immune system, called CD4 cells or T cells. 

Over time, HIV can destroy so many of these cells that the body cannot fight off infections and disease. When this occurs, HIV infection can lead to acquired immune deficiency syndrome (AIDS). 

AIDS is hailed as one of the most devastating diseases in the history of humanity.

Around 50,000 people become infected with HIV each year in the US, with 1.1 million Americans living with HIV; of these, around 16% do not know they are infected.

The study divulges that since the first transmission to humans by the great apes, the pathogen responsible, HIV has infected 75 million people.

The existence of AIDS has been known for 30 years. However, little had been concluded in that time regarding the chain of events that caused the global pandemic.

An international team, led by the universities of Oxford and Louvain in collaboration with Institut de recherche pour le développement (IRD) researchers, has recreated the epidemic's genetic history through the use of genome sequencing of the virus and the latest phylogeographic techniques.

Previously, scientists identified chimpanzees from South Cameroon as the source of AIDS. Throughout history, great apes have been the source of several human contaminations, yet only one of these cases escalated to the spread of HIV to humans.

Researchers compared the genetic diversity of the viruses collected in the countries of the Congo Basin - the considered potential birthplace of the disease.

Kinshasa crowned as the geographical origin of HIV

The results of the research deem the origin of the virus from Kinshasa, the capital of what is now the Democratic Republic of the Congo. 

Kinshasa was the focus of early transmission and the source of pre-1960 pandemic viruses that spread elsewhere. Location and dating estimates were validated using the earliest HIV-1 archival sample, also from Kinshasa.

With the geographical origin determined, scientists linked genetic data on the virus' evolution with historical data. The aim of the linkage was to ascertain the circumstances behind the outbreak in Kinshasa and by what means it spread among human populations.

Trade and transport responsible for HIV spread

Baffling to researchers was the fact that the human epidemic broke out in the Congolese capital and not in Cameroon, where the chimpanzees that contaminated humans are found.

The explanation for this, according to researchers, has been found in Belgian colonial archives on the former Zaire. At the early stages of the century, vast amounts of trade took place by river for markets such as ivory and rubber, which encouraged movement between Southeast Cameroon and Kinshasa.

The AIDS epidemic has spread with the development of transport, including rail, as here in the Republic of Congo in 1967.
Image source: IRD - A. Dessier

1920s

The urbanization and development of transport - railways in particular - are thought to have made matters worse between 1920 and 1950, due to Kinshasa becoming one of the most connected cities in Central Africa.

1940s

Data suggest that by the end of the 1940s, over 1 million people passed through Kinshasa each year to reach the north or south of the country or to travel to neighboring countries.

The cocktail of trade and transport factors, combined with the virus' genetic adaptability, led to the rapid spread of the virus throughout the country and additional outbreaks in South and East Africa.

1960s

Following the 1960s, social changes including the rise of prostitution and the use of non-sterile hygienic needles in public health initiatives almost certainly contributed to the transformation of small-scattered outbreaks of infection into an unquestionable pandemic.

Scientists recently reported that the global burden of HIV, malaria and TB has decreased since the "Millennium Declaration." HIV in particular has declined every year, from 2.8 million new infections in 1997 to current annual rates of 1.8 million new infections.