By Craig Timberg and Daniel Halperin
Monday, February 27, 5:55 PM
We are unlikely to ever know all the details of the
birth of the AIDS epidemic. But a series of recent
genetic discoveries have shed new light on it, starting
with the moment when a connection from chimp to human
changed the course of history.
We now know where the epidemic began: a small patch of
dense forest in southeastern
within a couple of decades on either side of 1900. We
have a good idea of how: A hunter caught an infected
chimpanzee for food, allowing the virus to pass from
the chimp's blood into the hunter's body, probably
through a cut during butchering.
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
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
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
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
sprawling country with bustling
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
searching for the simian virus in chimp feces collected
across a vast swath of southern
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.
It was in these two stations where Hahn and Sharp's
team discovered samples of the simian virus that was
almost a perfect match for the HIV-1 group M that
eventually killed tens of millions of humans.
This discovery, published in the journal Science in
2006, intensified the quest for a birth date for the
virus. Again, genetic research offered the key clues.
Scientists had long known that a blood sample,
preserved from 1959, showed that HIV had been
several decades before the virus first drew
international attention in the 1980s. In 2008,
evolutionary biologist Michael Worobey sharpened that
picture when he reported in the journal Nature the
discovery of a second sample of the virus, trapped in a
wax-encased lymph node biopsy from 1960.
By comparing these two historic pieces of virus and
mapping out the differences in their genetic structures
in his lab at the
determined that HIV-1 group M was much older than
anyone had thought. Both samples of the virus appeared
to have descended from a single ancestor at some time
between 1884 and 1924. The most likely date was 1908.
Taken together, these two discoveries offered the
clearest clues to the birth and early life of the epidemic.
Not far from where HIV-1 group M was born was a major
river, the Sangha, flowing toward the heart of Central
navigation because of its ribbons of sandbars and the
dense vegetation along its banks.
In the especially treacherous middle section, near
where Hahn and Sharp's team found the viral ancestor of
HIV, few major human settlements ever developed. But
there were numerous communities on the Sangha's more
accessible stretches. And due south, past riverside
trading towns, was the mighty
Once the virus made the jump from chimp to human, a
single infected person could have carried HIV down the
Sangha, onto the Congo River and into
Belgians had founded the city in 1881, during what
historians call "The Scramble for
colonial powers carved up the continent into areas of
influence. By the early 20th century
A final, powerful bit of evidence supported the theory
Scientists studying HIV-1 group M already had found
many related varieties, what scientists call subtypes,
each with slightly different genetic structures and
paths through the world. One, scientists discovered,
had traveled east from
One went south to
One hopped all the way across the ocean to
Many others traveled not very far at all, staying in
genetic histories of these varieties and built an
extensive family tree for HIV, they all appeared to
have spread from a single explosion, a big bang of the
AIDS epidemic: Ground Zero was
Ivory and rubber
Powering the big bang was the burgeoning trade of
Ivory may seem a touch quaint today, but in its heyday
it was seen as beautiful, versatile and essential to
many everyday products. It was used to make billiard
balls, jewelry and cutlery. Furniture makers
incorporated it into their cabinets, artists into their
statues. Bagpipe makers used ivory for mounts,
ferrules, buttons and mouthpieces.
When supplies of ivory gradually grew short, as
colonial agents killed the once plentiful elephants by
the thousands, rubber took its place as the economic
lifeblood of colonialism in the
inflatable rubber tires for bicycles became popular in
the 1890s. Mass production of cars soon spiked demand
for rubber tires again.
The only obstacle to European companies' reaping huge
profits was that collecting ivory and rubber required
massive amounts of labor. Getting ivory from an
elephant meant stalking the animal, killing it and
cutting off its tusks. Getting rubber from vines
required slashing them, collecting the oozing white sap
and drying it -- sometimes on the collector's own skin.
The solution to the manpower demands soon became
obvious. Colonial powers created what was essentially
slavery: cheap muscle at the point of a gun.
This approach was not confined to collecting ivory and
rubber. These industries created tremendous new needs
for infrastructure to get goods to oceangoing ships
along the Atlantic coast. That meant African porters
had to carry goods and supplies anyplace the steamboats
Workers were needed to build railroads, trading
stations, dormitories. And somebody needed to operate
the steamboats, load the railroad cars, carry the tusks
or gobs of rubber in from the jungle. When workers
became unruly, the colonial companies deployed heavily
armed soldiers to keep the cogs of these vast
All these roles were filled by Africans, many imported
from villages hundreds or even thousands of miles away.
African life here was beyond cheap. It was disposable.
Contemporary accounts by journalists and missionaries
tell of colonial officials across the
ordering mass slaughters and the torching of restive
villages while creating forced settlements that
resembled nothing so much as concentration camps.
The role of African porters
In December 1895 German colonial authorities heard
fabulously rich ivory and rubber stocks awaiting exploitation.
The Germans soon after gave authority to a colonial
company to take control of the region by force. Over
the next four years they extended their power all the
way through southeastern
trading station on the
upstream from where its waters merged with the Sangha.
In the wedge of land defined by these two rivers, HIV
either had just been born or soon would be.
The trading station was called Moloundou, and a busy
town remains there today. But at the time it was almost
unimaginably remote. Few human settlements had
developed among these forbidding forests. And there
were only two practical ways out: by steamship down the
Ngoko to the Sangha and on to the
overland by foot to the
The river route was the easier of the two, and
steamships transported the bulk of the ivory and rubber
collected in southeastern
were necessary to connect Moloundou with other trading
stations and inland areas rich with rubber and ivory.
For these journeys the bounty was borne by Africans who
carried loads averaging 55 pounds each. At the peak of
the foot traffic that would develop between inland
areas and the coast, the busy way station recorded more
than a thousand porters passing by on a typical day.
Trade routes, disease routes
Ominously, something else followed the rubber trade
and skin infections were the most obvious.
Colonial authorities attempted mass inoculation
campaigns for smallpox and set up quarantine zones that
restricted where the porters were allowed to travel.
But even so, the diseases spread.
Among them was syphilis, which arrived with the
Europeans. In just a few years it reached epidemic
proportions along porter routes and riverside trading
impossible now to determine how much of this spread
resulted from rapes as opposed to other kinds of
encounters, but it's clear that colonial commerce
created massive new networks of sexual interactions --
and massive new transmissions of infections. (In later
decades, transmission through the reuse of hypodermic
needles in medical care probably had some role in HIV's
spread as well.)
So HIV's first journey looked something like this: A
hunter killed an infected chimp in the southeastern
Cameroonian forest, and a simian virus entered his body
through a cut during the butchering, mutating into HIV.
This probably had happened many times before, during
the centuries when the region had little contact with
the outside world. But now thousands of porters -- both
men and women -- were crossing through the area
regularly, creating more opportunities for the virus to
travel onward to a riverside trading station such as Moloundou.
One of the first victims -- whether a hunter, a porter
or an ivory collector -- gave HIV to a sexual partner.
There may have been a small outbreak around the trading
station before the virus found its way aboard a
steamship headed down the
For this fateful journey south, HIV could have ridden
in the body of these first victims, or it could have
been somebody infected later: a soldier or a laborer.
Or it could have been carried by a woman: a concubine,
It's also possible that the virus moved down the river
in a series of steps, maybe from Moloundou to Ouesso,
then onward to Bolobo on the
There might even have been a series of infections at
trading towns along the entire route downriver. Yet
even within these riverside trading posts HIV would
have struggled to create anything more than a
short-lived, localized outbreak.
Most of this colonial world didn't have enough
potential victims for such a fragile virus to start a
major epidemic. HIV is harder to transmit than many
other infections. People can have sex hundreds of times
without passing the virus on. To spread widely, HIV
requires a population large enough to sustain an
outbreak and a sexual culture in which people often
have more than one partner, creating networks of
interaction that propel the virus onward.
To fulfill its grim destiny, HIV needed a kind of place
never before seen in
was rising in the heart of the region: a big, thriving,
hectic place jammed with people and energy, where old
rules were cast aside amid the tumult of new commerce.
a mere outbreak. It was here that AIDS grew into an epidemic.
Laying the scientific story alongside the historical
one offers one final revelation. In the 1920s, as
railroads became widely available, the
value as a steamship route dwindled sharply. Global
rubber prices also collapsed. The pace of human
movement through the region eased.
So the improbable journey of the killer strain of HIV
was feasible for only a few hectic decades, from the
1880s to the 1920s. Without "The Scramble for
it's hard to see how HIV could have made it out of
millions of people. Even a delay might have caused the
killer strain of HIV to die a lonely death deep in the forest.
From "Tinderbox" by Craig Timberg and Daniel Halperin.
Reprinted by arrangement with The Penguin Press, a
member of Penguin Group (USA) inc. Copyright (c) Craig
Timberg and Daniel Halperin, 2012. Timberg, a former
foreign correspondent in
security editor of The
senior HIV prevention adviser in the
global AIDS program and is now an epidemiologist at the
(c) The Washington Post Company