BIOLOGY- Tuberculosis

BIOLOGY- Tuberculosis

by Shoaib


What is tuberculosis (TB)?

Tuberculosis, also called TB, is an infectious disease caused by a bacterium named Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs  but can infect almost any organ in the body.Tuberculosis is spread from person to person through the air. Tuberculosis can be curable with antibiotics that are r available in countries such as the U.S. and europe. According to the World Health Organization (WHO), nearly 2 billion people—one–third of the world's population—have tuberculosis.Annually, 8 million people become ill with tuberculosis, and 2 million people die from the disease worldwide. In 2004, around 14.6 million people had active TB disease with 9 million new cases.

How is TB spread?

TB spreads when someone who has pulmonary TB coughs. TB bacteria from that person's lungs are then expelled into the air and may be inhaled into the lungs of another person. TB is not very infectious; it's much harder to catch than the common cold. Usually a lot of time needs to be spent with a person with pulmonary TB for someone to catch TB. It's not possible to get TB from sharing a glass with a person with TB or touching a doorknob after someone with TB has used it. Also, once a person with TB is on medication he or she quickly becomes non-contagious. People on medication can quickly resume their normal patterns of life without fear of spreading TB to others.


What are the signs and symptoms of TB?


According to Wikipedia In the patients where TB becomes an active disease, 75% of these cases affect the lungs, where the disease is called pulmonary TB. Symptoms include a productive, prolonged cough of more than three weeks duration, chest pain and coughing up blood. These symptoms usually come on gradually over a period of weeks. The most common symptoms are:
  • cough, (usually for more than 3 weeks)
  • coughing up blood or sputum (phlegm from deep inside the lungs) pain in the chest
  • fatique
  • weight loss
  • fever
  • night sweats


How do you treat active TB and  what is TB infection and how do you treat it?

To treat TB several antibiotics need to be taken together over a period of usually 6 months to a year. For this treatment to work it's vital that these medicines be taken regularly and that the treatment be completed. Lengthy treatment is necessary because it is difficult to eradicate TB bacteria from the body. TB infection means someone has bacteria sleeping in their body. They're not sick or contagious because the bacteria are dormant. TB infection is detected when someone has a positive skin test but a normal chest x-ray and no other sign of tuberculosis disease. To kill these sleeping bacteria and to prevent the development of active disease, persons with TB infection are often advised to take several months of treatment, usually with only one or two medications.

What is the TB skin test?

The TB skin test is performed by injecting a small amount of testing liquid into the skin of the forearm. The test needs to be read 48 to 72 hours later by someone trained in reading skin tests. If it's positive then a chest x-ray is done to rule out active disease. If the chest x-ray is normal then the person is likely to have TB infection. Once a skin test is positive it will most likely stay positive and should not be repeated. Unless a person develops symptoms one chest x-ray is all that's needed.


Who Should Get the Tuberculosis (TB) Skin Test (PPD, Mantoux)?
Anyone who has an elevated risk of TB from coming into contact with people who have this disease should get tested. This includes people who:

  • have any symptoms that could be compatible with TB
  • are in the health fields
  • spend time around potentially infectious people (e.g. work in a homeless shelter or prison)
  • come from, or have travel to, parts of the world where TB is more common than in the U.S. - this would include almost all parts of Asia, South and Central America, Africa, East Europe
  • have immune systems that are not properly working (e.g. AIDS, cancers).

Even those who have taken BCG (TB immunization in childhood) can safely get a PPD.



TB can be prevented and controled if two approaches are taken in consideration. In the first, people with TB and their contacts are identified and then treated. Identification of infections often involves testing high-risk groups for TB. In the second approach, children are vaccinated to protect them from TB. Unfortunately, no vaccine is available that provides reliable protection for adults. However, in tropical areas where the incidence of atypical mycobacteria is high, exposure to nontuberculous mycobacteria gives some protection against TB.

What Countries have a High Incidence of TB?
It is easier to identify countries of low rather than high TB incidence.  Therefore, individuals should undergo TB screening if they arrived from countries EXCEPT those on the following list: Canada, Jamaica, Saint Kitts and Nevis, Saint Lucia, Virgin Islands, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Liechtenstein, Luxembourg, Malta, Monaco, Netherlands, Norway, San Marino, Sweden, Switzerland, United Kingdom, American Samoa, Australia, or New Zealand.

 How important is TB today?

Tuberculosis kills more people today than any other infectious disease. About 2 million people a year die from TB worldwide. However, death from TB is rare in the United States. King County reports 120-150 cases of people with active TB per year and of these people the cure rate is almost one hundred percent.





World Health Organization (WHO). Tuberculosis Fact sheet N°104 - Global and regional incidence. March 2006, Retrieved on 6 October 2006.

Tuberculosis The Merck Manual

Wikipedia ( Tuberculosis

Centers for Disease Control and Prevention (CDC), Division of Tuberculosis Elimination. Core Curriculum on Tuberculosis: What the Clinician Should Know. 4th edition (2000). Updated Aug 2003.

Fine P, Floyd S, Stanford J, Nkhosa P, Kasunga A, Chaguluka S, Warndorff D, Jenkins P, Yates M, Ponnighaus J (2001). "Environmental mycobacteria in northern Malawi: implications for the epidemiology of tuberculosis and leprosy". Epidemiol Infect 126 (3): 379-87. PMID 11467795. 


Chest X-ray of a patient suffering from Tuberculosis