News / Africa

TB Origins Found in Africa

A patient who tested positive for extreme drug resistant tuberculosis (XDR-TB) awaits treatment at a rural hospital at Tugela Ferry in South Africa's impoverished KwaZulu Natal province, (File photo).
A patient who tested positive for extreme drug resistant tuberculosis (XDR-TB) awaits treatment at a rural hospital at Tugela Ferry in South Africa's impoverished KwaZulu Natal province, (File photo).

Multimedia

Audio
TEXT SIZE - +
Joe DeCapua
The origins of humans have been traced to Africa. And now, so have the origins of tuberculosis. New research shows the evolutionary trees of both humans and TB have grown side-by-side.


TB bacteria originated in Africa at least 70,000 years ago. That’s the finding of a team of researchers led by Professor Sebastien Gagneaux of the Swiss Tropical and Public Health Institute. But why study the history of TB?

Gagneaux said, “At the end of the day, it’s a certain kind of historic question and there have been long discussions about where TB came from originally. That’s on the one hand. On the other hand, the idea is that by learning from the past and how infectious disease evolves over time, this potentially could give us some clue about the future of the TB epidemic.”

To trace the origins of TB researchers relied on genetic material, which is relatively easy to come by.

“The trick is to use the genomic information that we can get from bacteria living today. That’s an approach which has been used for all kinds of other organisms, including humans, themselves. So we actually are learning a lot from what people are doing with human genetics,” he said.

Gagneaux said that the evolutionary trees of humans and TB probably did more than just grow side by side.

“I think that’s a nice way to put it. Maybe you can even say one inside the other. Imagine where the TB bacteria live, which is actually inside of human bodies. Yes, side by side, or one inside the other.”

Humans have bacteria on them and in them all the time. In fact, they help keep us alive. Researchers are trying to determine if tuberculosis bacteria were always harmful to humans.

“That’s also something that we’re trying to address in this work because there’s this striking feature in tuberculosis, which is this phenomena called latency – so-called latent infection -- meaning that people can carry these bacteria. So they’re actually infected without having any symptoms of disease. This latency period can last for several decades. Most of the people, who are actually carrying these bacteria, will actually never develop so-called active tuberculosis,” he said.

Studies are trying to determine why only five to ten percent of the estimated two billion people infected with the bacteria actually come down with active tuberculosis.

Another question is whether the bacteria were at one time beneficial to humans?

“Obviously, there seems to be something special about these five to ten percent of people who are coming down. Maybe that’s just bad luck. We know there are obvious very strong risk factors, such as HIV co-infection or malnutrition. Diabetes is also a factor, which can increase your risk of developing active tuberculosis once you have been infected. But again this idea that maybe carrying these bacteria in this latent form could potentially be beneficial because it might protect against other diseases. Again, that’s a very provocative hypothesis, which we, however, cannot completely neglect.”

Gagneaux said TB left Africa when humans did, about 65,000 to 70,000 years ago. Then, about 10,000 years ago, came the Neolithic Demographic Transition. It’s the time when people started to develop agriculture and domesticate animals. But it was also a time when diseases jumped from domesticated animals to humans for the first time. Gagneaux says for many years it was assumed that TB took the same path – from animals to humans. However, the research shows that TB in humans pre-dates the domestication of animals. It’s particularly adapted to live inside humans and can’t really survive on its own in the environment.

There was another important development during the Neolithic Demographic Transition. Humans started to form settlements that were densely populated. It’s an ideal situation for the spread of tuberculosis through the air from human to human.

“Because of these changes in these human behaviors and numbers, potentially TB might have become more virulent in the sense of causing disease maybe more quickly or maybe a more deadly disease. It’s true that TB is very deadly nowadays. So if you don’t treat it, kills up to 50 percent of people who actually have active tuberculosis,” Gagneaux said.

He added that before settlements, in the hunter-gatherer days, perhaps TB was not as deadly.

“Overly deadly would be a bad strategy for any pathogen because you might just kill off all susceptible hosts and you might end up with nobody else to infect. And so only once through this Neolithic transition -- when more and more people were actually living close by -- TB maybe evolved in a way to be able to become more virulent and take advantage, if you will, of this increasing number of susceptible people to infect.”

After humans left Africa, they started to change in appearance as they adapted to their new geographical locations. TB also evolved and now there are many different strains of bacteria that cause the disease. The strain found in South Africa differs from that found in China, for example. Africa, though, still has the greatest diversity of TB strains.

Researchers hope that knowing the evolutionary history of TB will help in the development of new drug treatments and vaccines. Currently, the number of drug-resistant TB cases is growing. The knowledge may also help predict “future patterns of the disease.”

You May Like

Multimedia Relatives of South Korean Ferry Victims Fire at Authorities

46 people are confirmed dead, but some 250 remain trapped inside sunken ferry More

War Legacy Haunts Vietnam, US Relations

$84 million project aims to clean up soil contaminated by Agent Orange More

Wikipedia Proves Useful for Tracking Flu

Technique gave better results than Center for Disease Control (CDC) and Google’s Flu Trends More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Ukraine, Russia, United in Faith, Divided in Politicsi
X
Michael Eckels
April 19, 2014
There is a strong historical religious connection between Russia and Ukraine. But what role is religion playing in the current conflict? In the run-up to Easter, Michael Eckels in Moscow reports for VOA.
Video

Video Ukraine, Russia, United in Faith, Divided in Politics

There is a strong historical religious connection between Russia and Ukraine. But what role is religion playing in the current conflict? In the run-up to Easter, Michael Eckels in Moscow reports for VOA.
Video

Video Face of American Farmer is Changing

The average American farmer is now 58 years old, and farmers 65 and older are the fastest growing segment of the population. It’s a troubling trend signaling big changes ahead for American agriculture as aging farmers retire. Reporter Mike Osborne says a new report from the U.S. Census Bureau is suggesting what some of those changes might look like... and why they might not be so troubling.
Video

Video Donetsk Governor: Ukraine Military Assault 'Delicate But Necessary'

Around a dozen state buildings in eastern Ukraine remain in the hands of pro-Russian protesters who are demanding a referendum on self-rule. The governor of the whole Donetsk region is among those forced out by the protesters. He spoke to VOA's Henry Ridgwell from his temporary new office in Donetsk city.
Video

Video Drones May Soon Send Data From High Seas

Drones are usually associated with unmanned flying vehicles, but autonomous watercraft are also becoming useful tools for jobs ranging from scientific exploration to law enforcement to searching for a missing airliner in the Indian Ocean. VOA’s George Putic reports on sea-faring drones.
Video

Video New Earth-Size Planet Found

Not too big, not too small. Not too hot, not too cold. A newly discovered planet looks just right for life as we know it, according to an international group of astronomers. VOA’s Steve Baragona has more.
Video

Video Copts in Diaspora Worry About Future in Egypt

Around 10 percent of Egypt’s population belong to the Coptic faith, making them the largest Christian minority in the Middle East. But they have become targets of violence since the revolution three years ago. With elections scheduled for May and the struggle between the Egyptian military and Islamists continuing, many Copts abroad are deeply worried about the future of their ancient church. VOA religion correspondent Jerome Socolovsky visited a Coptic church outside Washington DC.
Video

Video Critics Say Venezuelan Protests Test Limits of Military's Support

During the two months of deadly anti-government protests that have rocked the oil-rich nation of Venezuela, President Nicolas Maduro has accused the opposition of trying to initiate a coup. Though a small number of military officers have been arrested for allegedly plotting against the government, VOA’s Brian Padden reports the leadership of the armed forces continues to support the president, at least for now.
Video

Video More Millenials Unplug to Embrace Board Games

A big new trend in the U.S. toy industry has more consumers switching off their high-tech gadgets to play with classic toys, like board games. This is especially true among the so-called millenial generation - those born in the 1980's and 90's. Elizabeth Lee has more from an unusual café in Los Angeles, where the new trend is popular and business is booming.
Video

Video Google Buys Drone Company

In its latest purchase of high-tech companies, Google has acquired a manufacturer of solar-powered drones that can stay in the air almost indefinitely, relaying broadband Internet connection to remote areas. It is seen as yet another step in the U.S. based Web giant’s bid to bring Internet to the whole world. VOA’s George Putic reports.
AppleAndroid