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Tuberculosis

Causes of Tuberculosis

Learn about causes of tuberculosis.All cases of TB are passed from person to person via droplets. When someone with TB infection coughs, sneezes, or talks, tiny droplets of saliva or mucus are expelled into the air, which can be inhaled by another person.

  • Once infectious particles reach the alveoli (small saclike structures in the air spaces in the lungs), another cell, called the macrophage, engulfs the TB bacteria.


    • Then the bacteria are transmitted to the lymphatic system and bloodstream and spread to other organs occurs.


    • The bacteria further multiply in organs that have high oxygen pressures, such as the upper lobes of the lungs, the kidneys, bone marrow, and meninges -- the membrane-like coverings of the brain and spinal cord.

Learn more about causes of tuberculosis »

Tuberculosis Overview

Tuberculosis (TB) describes an infectious disease that has plagued humans since the Neolithic times. Two organisms cause tuberculosis -- Mycobacterium tuberculosis and Mycobacterium bovis.

Physicians in ancient Greece called this illness "phthisis" to reflect its wasting character. During the 17th and 18th centuries, TB caused up to 25% of all deaths in Europe. In more recent times, tuberculosis has been called "consumption."

  • Robert Koch isolated the tubercle bacillus in 1882 and established TB as an infectious disease.


    • In the 19th century, patients were isolated in sanatoria and given treatments such as injecting air into the chest cavity. Attempts were made to decrease lung size by surgery called thoracoplasty.


    • During the first half of the 20th century, no effective treatment was available.


    • Streptomycin, the first antibiotic to fight TB, was introduced in 1946, and isoniazid (Laniazid, Nydrazid), originally an antidepressant medication, became available in 1952.

  • M. tuberculosis is a rod-shaped, slow-growing bacterium.


    • M. tuberculosis' cell wall has high acid content, which makes it hydrophobic, resistant to oral fluids.


    • The cell wall of Mycobacteria absorbs a certain dye used in the preparation of slides for examination under the microscope and maintains this red color despite attempts at decolorization, hence the name acid-fast bacilli.

  • M. tuberculosis continues to kill millions of people yearly worldwide. In 1995, 3 million people died from TB.


    • More than 90% of TB cases occur in developing nations that have poor hygiene and health-care resources and high numbers of people infected with HIV.


  • In the United States, the incidence of TB began to decline around 1900 because of improved living conditions.


    • TB cases have increased since 1985, most likely due to the increase in HIV infection.


  • Tuberculosis continues to be a major health problem worldwide. In 2008, the World Health Organization (WHO) estimated that one-third of the global population was infected with TB bacteria.


    • 8.8 million new cases of TB developed.


    • 1.6 million people died of this disease in 2005.


    • Each person with untreated active TB will infect on average 10-15 people each year.


    • A new infection occurs every second.


    • In 2009, the TB rate in the United States was 3.8 cases per 100,000 population, a slight decrease from the prior year. Four states (California, Florida, New York, and Texas) accounted for the majority of all new TB cases (50.3%).


  • With the spread of AIDS, tuberculosis continues to lay waste to large populations. The emergence of drug-resistant organisms threatens to make this disease once again incurable.


  • In 1993, the WHO declared tuberculosis a global emergency.


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Tuberculosis

Cough »

Coughs Overview

A cough is an action your body takes to get rid of substances that are irritating to your air passages, which carry the air you breathe in from the nose and mouth to the lungs. A cough occurs when special cells along the air passages get irritated and trigger a chain of events. The result? Air in your lungs is forced out under high pressure. You can choose to cough (a voluntary process), or your body may cough on its own (an involuntary process).

Causes of Coughs

The list of possible causes of cough is long and highly varied. Doctors classify coughs into 2 categories, acute and chronic. Many doctors define an acute cough as one that been present for less than 3 weeks. Chronic coughs are those present for more than 3 weeks.

  • Acute coughs can be divided into infectious (caused by an infection) and noninfectious causes.
  • Infectious causes of acute cough include viral upper respir...

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Tuberculosis »

Tuberculosis (TB) is the most common cause of infectious disease–related mortality worldwide.

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