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

Turkey's Controversial Reform Bill Giving Investors Jitters

Homeland security reform bill will give police new powers in search, seizure, detention and arrests, while restricting the rights of suspects, their attorneys More

Audio Slideshow In Kenyan Prison, Good Grades Are Path to Freedom

Some inmates who get high marks could see their sentences commuted to non-custodial status More

Ali Regained Title in Historic Fight 40 Years Ago

'The Champ' knocked Foreman out to regain crown he had lost 7 years earlier when US government accused him of draft-dodging and boxing officials revoked his license More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Victorious Secularists Face Challenge to Form Government in Tunisiai
X
Henry Ridgwell
October 30, 2014 11:39 PM
Official results from Tunisia show the Islamist Ennahda party has failed to win the second free election since the so-called "Arab Spring" uprising in 2011. Ennahda, which handed power to a government of technocrats pending the elections, lost out to the secular party Nidaa Tounes. Henry Ridgwell reports from London that the relatively peaceful poll offers some hope in a volatile region.
Video

Video Victorious Secularists Face Challenge to Form Government in Tunisia

Official results from Tunisia show the Islamist Ennahda party has failed to win the second free election since the so-called "Arab Spring" uprising in 2011. Ennahda, which handed power to a government of technocrats pending the elections, lost out to the secular party Nidaa Tounes. Henry Ridgwell reports from London that the relatively peaceful poll offers some hope in a volatile region.
Video

Video Africa Tells its Story Through Fashion

In Africa, Fashion Week is a riot of colors, shapes, patterns and fabrics - against the backdrop of its ongoing struggle between nature and its fast-growing urban edge. How do these ideas translate into needle and thread? VOA’s Anita Powell visited this year’s Mercedes Benz Fashion Week Africa in Johannesburg to find out.
Video

Video Smugglers Offer Cheap Passage From Turkey to Syria

Smugglers in Turkey offer a relatively cheap passage across the border into Syria. Ankara has stepped up efforts to stem the flow of foreign fighters who want to join Islamic State militants fighting for control of the Syrian border city of Kobani. But porous borders and border guards who can be bribed make illegal border crossings quite easy. Zlatica Hoke has more.
Video

Video China Political Meeting Seeks to Improve Rule of Law

China’s communist leaders will host a top level political meeting this week, called the Fourth Plenum, and for the first time in the party’s history, rule of law will be a key item on the agenda. Analysts and Chinese media reports say the meetings could see the approval of long-awaited measures aimed at giving courts more independence and include steps to enhance an already aggressive and high-reaching anti-corruption drive. VOA’s Bill Ide has more from Beijing.
Video

Video After Decades of Pressure, Luxembourg Drops Bank Secrecy Rules

European Union finance ministers have reached a breakthrough agreement that will make it more difficult for tax cheats to hide their money. The new legislation, which had been blocked for years by countries with a reputation as tax havens, was approved last week after Luxembourg and Austria agreed to lift their vetoes. But as Mil Arcega reports, it doesn’t mean tax cheats have run out of places to keep their money hidden.
Video

Video Kobani Refugees Welcome, Turkey Criticizes, US Airdrop

Residents of Kobani in northern Syria have welcomed the airdrop of weapons, ammunition and medicine to Kurdish militia who are resisting the seizure of their city by Islamic State militants. The Turkish government, however, has criticized the operation. VOA’s Scott Bobb reports from southeastern Turkey, across the border from Kobani.

All About America

AppleAndroid