Tuberculosis is for sure one of the deadliest and common major infectious disease today .As of 2004 ,14.6 million people have active TB disease .Apart from this 9 million new cases and 2 million of more deaths are predicted .Rise in the number of people affected in the developed countries is due to their compromised immune systems.

Tuberculosis can mainly be charecterised into two parts Active TB and the Inactive or Latent TB. A person can have active or inactive TB. Active TB or TB disease means the bacteria are active in the body and the immune system is unable to stop them from causing illness. People can also be infected with TB that is not active in the body. Inactive TB infection is also called latent TB. If a person has latent TB, it means their body has been able to successfully fight the bacteria and stop them from causing illness.

Almost 90% of those infected have asymptomatic Latent TB infection(LTBI). There is 10% lifetime chance that LTBI will progress to TB disease which if untreated will kill more than 50% of its victims. TB is among the top 4 infectious killing disease in the world.

Latent TB Infection
TB bacteria sometimes manage to fool the immune system. With tuberculosis, the immune system can very quickly quiet the infection so that you have no symptoms and you are not contagious, but the "germ" is not completely eliminated from your body. This is called a "latent infection." People who have latent TB infection do not feel sick, do not have any symptoms, and cannot spread TB to others. But some people with latent TB infection go on to get TB disease.

The problem with tuberculosis is when the latent infection turns "active." In active TB, you may cough, feel lousy and lose weight over months. And you are contagious. Many people who have latent TB infection never develop active TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease.

Active TB Disease
TB is spread through the air from one person to another. The bacteria are put into the air when a person with active TB disease of the lungs or throat coughs or sneezes. People nearby may breathe in these bacteria and become infected. People with active TB disease can be treated and cured if they seek medical help. Even better, people with latent TB infection can take medicine so that they will not develop active TB disease.

Some people develop active TB disease soon after becoming infected, before their immune system can fight the TB bacteria. Other people may get sick later, when their immune system becomes weak for another reason.

People with active TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers. Symptoms of active TB disease include:

The best way to prevent active TB is to treat latent TB with antibiotics. The TB test involves the injection of a TB-like substance just under the surface of the skin, using a very small needle. About two days later, the area is examined for a red, rash-like reaction. The Immigration and Naturalization Service requires all immigrants be tested for TB.

Links:

National Institute of Allergy and Infectious Diseases
http://www.niaid.nih.gov/factsheets/tb.htm
 

Target Tuberuclosis
http://www.targettuberculosis.org.uk/whatisTB.htm