As to the why, here is where the story gets even more fascinating, and terrible. We typically think of diseases in terms of how they threaten us personally. But they have their own stories. Diseases are born. They grow. They falter, and sometimes they die. In every case these changes happen for reasons.
For decades nobody knew the reasons behind the birth of the AIDS epidemic. But it is now clear that the epidemic’s birth and crucial early growth happened during Africa’s colonial era, amid massive intrusion of new people and technology into a land where ancient ways still prevailed. European powers engaged in a feverish race for wealth and glory blazed routes up muddy rivers and into dense forests that had been traveled only sporadically by humans before.
The most disruptive of these intruders were thousands of African porters. Forced into service by European colonial powers, they cut paths through the exact area that researchers have now identified as the birthplace of the AIDS epidemic. It was here, in a single moment of transmission from chimp to human, that a strain of virus called HIV-1 group M first appeared.
In the century since, it has been responsible for 99 percent of all of the world’s deaths from AIDS — not just in Africa but in Moscow, Bangkok, Rio de Janeiro, San Francisco, New York, Washington. All that began when the West forced its will on an unfamiliar land, causing the essential ingredients of the AIDS epidemic to combine.
It was here, by accident but with motives by no means pure, that the world built a tinderbox and tossed in a spark.
The chimps of Cameroon
Many simians, such as gorillas and monkeys, can carry a virus that resembles HIV. But scientists now know that HIV-1 group M was born from a virus circulating among a community of chimpanzees concentrated in Cameroon, a sprawling country with bustling Atlantic Ocean ports, populous highlands, and a lightly developed southern region where relatively few people live even today. This was home to the chimps.
Finding a more exact location took a remarkable degree of scientific ingenuity. An international research team led by Beatrice Hahn of the University of Alabama at Birmingham and Paul Sharp of the University of Edinburgh developed an elaborate project that involved searching for the simian virus in chimp feces collected across a vast swath of southern Cameroon.
To find a strain of the simian virus that was, on a genetic level, essentially indistinguishable from the most lethal form of HIV, the research team set up 10 stations across the region. Two of the stations were in the particularly remote southeastern corner of the nation, as far as possible from major population centers.