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What makes TB the world's most infectious killer? - Melvin Sanicas

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In 2008, two 9,000-year old skeletons were found with their bones infected by an all too familiar bacterium. The ancient Greeks knew its effects as phthisis; the Incans called it chaky oncay; and today we call it tuberculosis, or TB. TB is still one of the world’s most infectious killers, causing more deaths than malaria or even HIV. How has it persisted for so long? Melvin Sanicas investigates.

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TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Melvin Sanicas
  • Director Katie Wendt
  • Narrator Addison Anderson
  • Producer Aaron Augenblick
  • Animator Mimi Chiu
  • Music GDM Production Music
  • Director of Production Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Associate Producer Bethany Cutmore-Scott
  • Associate Editorial Producer Dan Kwartler
  • Script Editor Emma Bryce
  • Fact-checker Eden Girma
  • See more
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No other disease has had such a strong influence on music, film, art, and literature than tuberculosis (TB), a bacterial infection with Mycobacterium tuberculosis (MTb) that most commonly affects the lungs but can affect any organ in the body. It has plagued mankind throughout known history and has killed more than any other bacteria.

Evidence of TB infection in humans have been found in 9,000 year old Neolithic bone remains in Eastern Mediterranean and in Egyptian mummies dating to 2400 BCE. But a detailed genetic analysis of strains of TB bacteria from around the world revealed that the infectious agent originated with the emergence of Homo sapiens in Africa more than 70,000 years ago. Over time, the various cultures of the world gave the TB different names: phthisis (Greek), yaksma (India), chaky oncay (Incan), consumptione (Latin), consumption, ao 癆 (Chinese) each related to the "drying" or "consuming" effect also called cachexia or unintentional dramatic weight loss. Other symptoms of tuberculosis include coughing up blood, night sweats, chest pains, loss of appetite, and exhaustion.

In the 19th century, TB was dubbed the White Plague, because of extreme pallor of people infected. It was seen as a "romantic disease" and suffering from TB was thought to bestow people artistic and poetic qualities. Among those infected are major artistic figures such as the poets John Keats, Percy Bysshe Shelley, Edgar Allan Poe, Lord Byron; the composer Frédéric Chopin, and novelists Emily Brontë, Robert Louis Stevenson. The imagery of TB was also used by writers of popular fiction of the 19th century who began the literary tradition of vampirism. It was sometimes thought that people with symptoms of tuberculosis, wasting and extreme pallor, were victims of vampires or were vampires themselves.

It was not until 1882 when Robert Koch revealed the disease was caused by an infectious agent and in 1895 when Wilhelm Roentgen discovered the X-ray, which allowed physicians to diagnose and track the progression of TB. A vaccine called "BCG" (Bacille Calmette-Guérin) was first used in humans in 1921 and is still in use today. The modern era of tuberculosis treatment control was ushered by the discovery of streptomycin in 1944 and isoniazid in 1951. These antibiotics, plus improved living conditions, has pushed TB into the margins of developed countries, but in most of the developing world, it remains a major epidemic.

Roughly one-quarter of the world's population is infected with TB and about 90% of those are asymptomatic, latent TB infections. It is difficult to diagnose TB infection due to the small number of TB bacteria the person is infected with, as well as the poor performance of the available tests (skin reaction and blood-based tests). Around 10% will progress to TB disease when TB germs overwhelm the immune system
(common in children). TB is a slow growing disease that can take months or years for symptoms to appear. Latent TB wakes up and becomes active
for those with weak immune systems such as older people, those who are HIV positive, or have had organ transplants or chemotherapy. When they cough, sneeze, spit, or talk, they can spread TB to 10-15 people within a year, on average.

Most deaths from TB can be prevented with early diagnosis and appropriate treatment. Antibiotics can kill the infection but the treatment is lengthy, 4 to 9 months with 3 to 4 antimicrobial drugs that may give people side effects. Rifampin may cause red discoloration of urine and tears and harms the liver of alcoholics, ethambutol may causes eye problems (optic neuritis), pyrazinamide may cause gout and joint pain; isoniazid may cause peripheral neuropathy (nerve problems, numbness, tingling feet and hands) and skin reaction. Some stop taking the medication because of side effects others stop when they start to feel better. Access to treatment can be difficult in some countries while stigma towards TB can force people to delay treatment.

TB becomes multi-drug resistant when the germ is resistant to at least isoniazid and rifampin, the two most potent TB drugs. This occurs when patients do not complete the full course of the treatment, when health-care providers prescribe the wrong treatment, or when the supply of drugs is not available or is of poor quality. The development of new drugs to treat TB or drug-resistant TB or new vaccines to prevent disease or infection requires substantial investment and research.

Many people think of TB as a disease of the past, but in 2017 over 10 million people became sick with TB and 1.3 million people died from the disease – making it the world’s #1 infectious killer. Tuberculosis is closely linked to poverty, overcrowding and malnutrition. A combined strategy, including rapid diagnostics, safe and shorter treatments, newer vaccines, and improving living standards with an emphasis on the importance of good nutrition, decent housing, and human welfare will be necessary to eradicate this scourge.

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About TED-Ed Animations

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Melvin Sanicas
  • Director Katie Wendt
  • Narrator Addison Anderson
  • Producer Aaron Augenblick
  • Animator Mimi Chiu
  • Music GDM Production Music
  • Director of Production Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Associate Producer Bethany Cutmore-Scott
  • Associate Editorial Producer Dan Kwartler
  • Script Editor Emma Bryce
  • Fact-checker Eden Girma
  • See more