Scientists using historical records and genetic sequencing to trace the origins of the HIV pandemic have stated that the urban change which began in Kinshasa during the 1920s resulted in the disastrous spread of the disease across Africa and the rest of the world.
Although the virus was probably passed from chimpanzees to human in the southern parts of Cameroon several years before, HIV was a regional infection until it reached the capital of what is now known as the Democratic Republic of the Congo.
Between the 1920s and 1960, the pandemic strain of HIV spread from Kinshasa to other nations beyond their borders and ultimately reached distant continents. The pandemic has infected almost 75 million people across the world.
At the time when the virus hit Kinshasa, it was a bustling city. Kinshasa was the biggest and fastest growing city in the region and had transport links across the country. The Congo River reached shores 600 miles away. The railways were busy carrying hundreds of workers southeast to Katanga, where immigrant miners were needs, and on to Lubumbashi which was more than 900 miles away.
By the time the 1940s set in, in excess of one million people were passing through Kinshasa annually, on the railway lines alone. According to research which has been published in Science, the rate of new HIV infection had surpassed the regional population growth by 1960.
Although the virus was being spread by the movement of trains and boats, there were other factors involved. Kinshasa had a disproportionate number of males and this resulted in a demand for sex workers. It is said that the virus may also have been spread further by doctors, who unknowingly did so by the use of unsterilized injections at sexual health clinics.
A global team of scientists, led by the universities of Leuven in Belgium and Oxford in Britain, reconstructed the HIV pandemic history by using DNA samples and historical records dating back to the latter part of the 1950s. The DNA gave them the opportunity to draft a family tree of the virus and they were able to trace its movement through time. By making use of statistical models, they were able to go back further than the 1950s and found that the pandemic started in Kinshasa in the 1920s.
At the time, those with HIV in central Africa did not show specific symptoms which would have been recorded in their medical records. The virus causes the collapse of the immune system and this leaves people susceptible to many infections. An evolutionary biologist based at Oxford University and a senior author of this study, Oliver Pybus, said for this type of epidemic where they are trying to find links prior to its discovery, genetics is the only real source of information available.
The genetic data that was available indicated that pandemic HIV spread very quickly through the Democratic Republic of the Congo, which is a country the size of Western Europe. From the latter part of the 1930s through to the early 1950s, the virus was spread by river and rail to Lubumbashi and Mbuji-Mayi in the south and to Kisangani in the north. At these points the virus spread and remained and it formed secondary clusters which allowed it to spread to other countries in eastern and southern Africa.
HIV was, at first, an infection confined to certain groups of people. However, the virus appeared to flourish and break out, affecting the general population and spreading globally. This happened after the Republic of Congo achieved independence during 1960.
Pybus said sections of this story may only be suggestive as without a time machine it is extremely difficult to prove causality. However, he is sure that they have the place and time correct. He said it appears that a combination of factors in Kinshasa during the early 20th century created a perfect situation for the entry of HIV, which led to a general epidemic moving at such a fast pace that it could not be stopped from affecting sub-Saharan Africa.
Various HIV strains have definitely crossed over from apes to humans via bush meat handling and hunting, several times throughout history. Only a few incidents have left traces which can be found in the DNA of HIV strains which are still around today. Some of the outbreaks infected hundreds of thousands of African people, but remained there. It is only one strain, known as HIV-1 group M, which became a pandemic.
Pybus said everyone wants to know how this could possibly have happened and how we got where we are today. The answer to why this one turned into a pandemic had to be found.
Image Credit: Jon Rawlinson