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

    Video Somali, AU Forces Face Resurgent Al-Shabab

    Somalia’s Western backers frustrated over country’s slow progress in establishing its armed forces to bring security after 25 years of chaos

    Israel Makes Push for Gaza Strip Recovery

    After years of economic blockade and attempts to disable Hamas, Israeli leaders eventually realized that Hamas’ downfall could lead to chaos or the rise of a more radical Jihadist group

    Slump in Chinese Tourists Hitting Hong Kong Retail

    Mainland Chinese account for up to three-quarters of visitors to Hong Kong, but that number is falling, and shopping centers are struggling to 'shift gears' and maintain sales

    By the Numbers

    Featured Videos

    Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
    Somali, African Union Forces Face Resurgent Al-Shababi
    X
    Henry Ridgwell
    April 28, 2016 4:20 PM
    The Islamic State terror group claimed its first attack in Somalia earlier this week, though the claim has not been verified by forces on the ground. Meanwhile, al-Shabab militants have stepped up their attacks as Somalia prepares for elections later this year. Henry Ridgwell reports there are growing frustrations among Somalia’s Western backers over the country’s slow progress in forming its own armed forces to establish security after 25 years of chaos.
    Video

    Video Somali, African Union Forces Face Resurgent Al-Shabab

    The Islamic State terror group claimed its first attack in Somalia earlier this week, though the claim has not been verified by forces on the ground. Meanwhile, al-Shabab militants have stepped up their attacks as Somalia prepares for elections later this year. Henry Ridgwell reports there are growing frustrations among Somalia’s Western backers over the country’s slow progress in forming its own armed forces to establish security after 25 years of chaos.
    Video

    Video Bangladesh Targeted Killings Spark Wave of Fear

    People in Bangladesh’s capital are expressing deep concern over the brutal attacks that have killed secular blogger, and most recently a gay rights activist and an employee of the U.S. embassy. Xulhaz Mannan, an embassy protocol officer and the editor of the country’s only gay and transgender magazine Roopban; and his friend Mehboob Rabbi Tanoy, a gay rights activist, were hacked to death by five attackers in Mannan’s Dhaka home earlier this month.
    Video

    Video Documentary Tells Tale of Chernobyl Returnees

    Ukraine this week is marking the 30th anniversary of the world's worst nuclear accident, at the Chernobyl nuclear power plant. Soviet officials at first said little about the accident, but later evacuated a 2,600-square-kilometer "exclusion zone." Some people, though, came back. American directors Holly Morris and Anne Bogart created a documentary about this faithful and brave community. VOA's Tetiana Kharchenko reports from New York on "The Babushkas of Chernobyl." Carol Pearson narrates.
    Video

    Video Nigerians Feel Bite of Buhari Economic Policy

    Despite the global drop in the price of oil, Nigerian President Muhammadu Buhari has refused to allow the country's currency to devalue, leading to a shortage of foreign exchange. Chris Stein reports from Lagos businessmen and consumers are feeling the impact as the country deals with a severe fuel shortage.
    Video

    Video  Return to the Wild

    There’s a growing trend in the United States to let old or underused golf courses revert back to nature. But as Erika Celeste reports from one parcel in Grafton, Ohio, converting 39 hectares of land back to green space is a lot more complicated than just not mowing the fairway.
    Video

    Video West Urges Unity in Libya as Migrant Numbers Soar

    The Italian government says a NATO-led mission aimed at stemming the flow of migrants from Libya to Europe could be up and running by July. There are concerns that the number of migrants could soar as the route through Greece and the Balkans remains blocked. Western powers say the political chaos in Libya is being exploited by people smugglers — and they are pressuring rival groups to come together under the new unity government. VOA's Henry Ridgwell reports.
    Video

    Video Russia’s TV Rain Swims Against Tide in Sea of Kremlin Propaganda

    Russia’s media freedoms have been gradually eroded under President Vladimir Putin as his government has increased state ownership, influence, and restrictions on critical reporting. Television, where most Russians get their news, has been the main target and is now almost completely state controlled. But in the Russian capital, TV Rain stands out as an island in a sea of Kremlin propaganda.
    Video

    Video Kurdish Town Receives Refugees but Lacks Resources

    A wave of refugees is pouring into the Kurdish town of Afrin in northern Syria as a result of fighting between rebel forces and Islamic State militants. VOA’s Amina Misto went to the town and reports local authorities are finding it difficult to cope with this influx of internally displaced people. Bronwyn Benito narrates her report.
    Video

    Video Scientists Build Human Tissue on Animal Matrix

    The question has always been, if a gecko can grow back its tail, why can't we regenerate our lost body parts? Well, maybe we can, someday. Scientists are moving towards the ability to rebuild fully functioning organs, and have made significant progress replacing muscles and other tissue.
    Video

    Video Containing Chernobyl Radiation Continues 30 Years After Explosion

    April 26 marks the 30th anniversary of the Chernobyl nuclear disaster. Hundreds were killed following the explosion and it's estimated that thousands more have died from cancers caused by the radiation. Henry Ridgwell traveled to Chernobyl and reports for VOA on the continuing efforts to decommission the site -- and on the fledgling plans for a new future in the vast exclusion zone.
    Video

    Video Frustration Builds Among Refugees Trapped at Macedonian Border

    On the Greek border with Macedonia, 12,000 refugees continue to wait. Since the route to the rest of Europe was closed last month, the makeshift camp at Idomeni has seen protests and tear gas. But while those here wait, their frustration grows — as do reports of people attempting to find new ways of continuing their journey. John Owens reports from Idomeni.
    Video

    Video Researchers: Bees Help Kenyan Farmers Fend Off Elephants

    Elephant crop-raiding continues to be a major source of human-wildlife conflict in Kenya, so one elephant researcher is helping to alleviate the problem near Tsavo East National Park with beehive fences, which use elephants’ natural aversion to bees to deter them from farms. VOA’s Jill Craig visited the area ahead of this month's Giants Club Summit, which will bring together dignitaries at Mount Kenya to find solutions to combat poaching, the No. 1 threat to elephants.

    Special Report

    Adrift The Invisible African Diaspora