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
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

Will Cuba Follow the Southeast Asia Model?

Decision to restore ties between US and Cuba has some debating whether it will lead to enhancement or regression of democracy for Communist island nation More

Kenyan Designer Finds Her Niche in Fashion Industry

‘Made in China’ fabrics underlie her success More

Report: CIA, Israel's Mossad Killed Senior Hezbollah Commander

The Washington Post story says Imad Mughniyah was killed instantly by a bomb "triggered remotely" from Tel Aviv by Mossad agents More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Jefferson's Library Continues to Impress, 200 Years Lateri
X
Deborah Block
January 31, 2015 12:12 AM
Two hundred years after the U.S. Congress purchased a huge collection of books belonging to former President Thomas Jefferson, it remains one of America’s greatest literal treasures and has become the centerpiece of Washington’s Library of Congress. VOA’s Deborah Block reports.
Video

Video Jefferson's Library Continues to Impress, 200 Years Later

Two hundred years after the U.S. Congress purchased a huge collection of books belonging to former President Thomas Jefferson, it remains one of America’s greatest literal treasures and has become the centerpiece of Washington’s Library of Congress. VOA’s Deborah Block reports.
Video

Video Egypt's Suez Canal Dreams Tempered by Continued Unrest

Egypt plans to expand the Suez Canal, raising hopes that the end of its economic crisis may be in sight. But some analysts say they expect the project may cost too much and take too long to make life better for everyday Egyptians. VOA's Heather Murdock reports.
Video

Video Threat of Creeping Lava Has Hawaiians on Edge

Residents of the small town of Pahoa on the Big Island of Hawaii face an advancing threat from the Kilauea volcano. Local residents are keeping a watchful eye on creeping lava. Mike O’Sullivan reports.
Video

Video Pro-Kremlin Youth Group Creatively Promotes 'Patriotic' Propaganda

As Russia's President Vladimir Putin faces international pressure over Ukraine and a failing economy, unofficial domestic groups are rallying to his support. One such youth organization, CET, or Network, uses creative multimedia to appeal to Russia's urban youth with patriotic propaganda. VOA's Daniel Schearf reports.
Video

Video Filmmakers Produce Hand-Painted Documentary on Van Gogh

The troubled life of the famous 19th century Dutch painter Vincent van Gogh has been told through many books and films, but never in the way a group of filmmakers now intends to do. "Loving Vincent " will be the first ever feature-length film made of animated hand-painted images, done in the style of the late artist. VOA’s George Putic reports.
Video

Video Issues or Ethnicity? Question Divides Nigeria

As Nigeria goes to the polls next month, many expect the two top presidential contenders to gain much of their support from constituencies organized along ethnic or religious lines. But are faith and regional blocs really what political power in Nigeria is about? Chris Stein reports.
Video

Video Rock-Consuming Organisms Alter Views of Life Processes

Scientists thought they knew much about how life works, until a discovery more than two decades ago challenged conventional beliefs. Scientists found that there are organisms that breathe rocks. And it is only recently that the scientific community is accepting that there are organisms that could get energy out of rocks. Correspondent Elizabeth Lee reports.
Video

Video Paris Attacks Highlight Global Weapons Black Market

As law enforcement officials piece together how the Paris and Belgian terror cells carried out their recent attacks, questions are being asked about how they obtained military grade assault weapons - which are illegal in the European Union. As VOA's Jeff Swicord reports, experts say there is a very active worldwide black market for these weapons, and criminals and terrorists are buying.
Video

Video Activists Accuse China of Targeting Religious Freedom

The U.S.-based Chinese religious rights group ChinaAid says 2014 was the worst year for religious freedom in China since the end of the Cultural Revolution. As Ye Fan reports, activists say Beijing has been tightening religious controls ever since Chinese leader Xi Jinping came to office. Hu Wei narrates.
Video

Video Theologians Cast Doubt on Morality of Drone Strikes

In 2006, stirred by photos of U.S. soldiers mistreating Iraqi prisoners, a group of American faith leaders and academics launched the National Religious Campaign Against Torture. It played an important role in getting Congress to investigate, and the president to ban, torture. VOA's Jerome Socolovsky reports.
Video

Video Former Sudan 'Lost Boy' Becomes Chess Master in NYC

In the mid-1980’s, thousands of Sudanese boys escaped the country's civil war by walking for weeks, then months and finally for more than a year, up to 1,500 kilometers across three countries. The so-called Lost Boys of the Sudan had little time for games. But one of them later mastered the game of chess, and now teaches it to children in the New York area. VOA’s Bernard Shusman in New York has his story.
Video

Video NASA Monitors Earth’s Vital Signs From Space

The U.S. space agency, NASA, is wrapping up its busiest 12-month period in more than a decade, with three missions launched in 2014 and two this month, one in early January and the fifth scheduled for January 29. As VOA’s Rosanne Skirble reports, the instruments being lifted into orbit are focused on Earth’s vital life support systems and how they are responding to a warmer planet.

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More

All About America

AppleAndroid