Jumat, 08 April 2011

What is tuberculosis?

Tuberculosis (TB) is an infectious disease caused by bacteria whose scientific name is Mycobacterium tuberculosis. It was first isolated in 1882 by a German physician named Robert Koch who received the Nobel Prize for this discovery. TB most commonly affects the lungs but also can involve almost any organ of the body. Many years ago, this disease was referred to as "consumption" because without effective treatment, these patients often would waste away. Today, of course, tuberculosis usually can be treated successfully with antibiotics.

There is also a group of organisms referred to as atypical tuberculosis. These involve other types of bacteria that are in the Mycobacterium family. Often, these organisms do not cause disease and are referred to as "colonizers" because they simply live alongside other bacteria in our bodies without causing damage. At times, these bacteria can cause an infection that is sometimes clinically like typical tuberculosis. When these atypical mycobacteria cause infection, they are often very difficult to cure. Often, drug therapy for these organisms must be administered for one and a half to two years and requires multiple medications.

How does a person get TB?

A person can become infected with tuberculosis bacteria when he or she inhales minute particles of infected sputum from the air. The bacteria get into the air when someone who has a tuberculosis lung infection coughs, sneezes, shouts, or spits (which is common in some cultures). People who are nearby can then possibly breathe the bacteria into their lungs. You don't get TB by just touching the clothes or shaking the hands of someone who is infected. Tuberculosis is spread (transmitted) primarily from person to person by breathing infected air during close contact.
There is a form of atypical tuberculosis, however, that is transmitted by drinking unpasteurized milk. Related bacteria, called Mycobacterium bovis, cause this form of TB. Previously, this type of bacteria was a major cause of TB in children, but it rarely causes TB now since most milk is pasteurized (undergoes a heating process that kills the bacteria)

Global and regional incidence

WHO estimates that the largest number of new TB cases in 2008 occurred in the South-East Asia Region, which accounted for 35% of incident cases globally. However, the estimated incidence rate in sub-Saharan Africa is nearly twice that of the South-East Asia Region with over 350 cases per 100 000 population.
An estimated 1.7 million people died from TB in 2009. The highest number of deaths was in the Africa Region.
In 2008, the estimated per capita TB incidence was stable or falling in all six WHO regions. However, the slow decline in incidence rates per capita is offset by population growth. Consequently, the number of new cases arising each year is still increasing globally in the WHO regions of Africa, the Eastern Mediterranean and South-East Asia.

Estimated TB incidence, prevalence and mortality, 2009

Uncertainty bounds for the table below are available in the Global tuberculosis control 2010 (Table 1, page 5).


Incidence1 Prevalence 2 Mortality (excl. HIV)
WHO region No. in thousands % of global total Rate per 100 000 pop3 No. in thousands Rate per 100 000 pop3 No. in thousands Rate per 100 000 pop3
Africa 2 800 30%  340 3 900  450  430  50
The Americas  270 2.9%  29  350  37  20 2.1
Eastern Mediterranean  660 7.1%  110 1 000  180  99  18
Europe  420 4.5%  47  560  63  62  7
South-East Asia 3 300 35%  180 4 900  280  480  27
Western Pacific 1 900 21%  110 2 900  160  240  13
Global total 9 400 100%  140 14 000  164 1 300  19
1 Incidence is the number of new cases arising during a defined period.
2 Prevalence is the number of cases (new and previously occurring) that exists at a given point in time.
3 Pop indicates population.

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