Tuberculosis (TB) remains a leading infectious killer
globally. TB is caused by Mycobacterium tuberculosis, which can
produce either a silent, latent infection or a progressive, active
disease. Left untreated or improperly treated, TB causes progressive
tissue destruction and, eventually, death. In contrast, TB remains out of
control in many developing countries—to the point that one third of the world’s
population currently is infected. Given increasing drug resistance, it is
critical that a major effort be made to control TB before the most potent drugs
are no longer effective.1

rates generally have risen with increasing urbanization and overcrowding
because it is easier for an airborne disease to spread when people are packed
closely together. Hence, TB became a significant pathogen in Europe during
the Middle Ages and peaked during the Industrial Revolution, when it caused
approximately 25% of all deaths in Europe and in the United States. This dire
threat led to the rise of public health departments and to procedures such
as the isolation of infected patients. Thus, TB was directly responsible for
many of the healthcare practices that we take for granted today. Unfortunately,
in developing nations, some of these practices are not widely available, and TB
continues to rage unabated.

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TB is a bacterial infection caused by Mycobacterium tuberculosis also referred
to as tubercle bacilli. The M. tuberculosis is a Gram-positive aerobic bacterium.
It is a small rod-like bacillus with a complex cell wall, which can withstand
weak disinfectants and survive in a dry state for weeks, but can only grow in a
host organism. It  most  commonly 
affects  the  lungs, 
producing  pulmonary  TB. However, transported by the blood or
lymphatic system, the TB bacilli can infect almost any part of the body,
including lymph glands, joints, kidneys, and bone – extrapulmonary TB. It is
critical to understand the disease,  its  aetiology 
and  its  epidemiology 
to  develop  a 
strong  TB control programme.
Early  symptoms  of 
pulmonary  TB  are 
often  vague  and 
easily attributable  to  other 
conditions,  with  the 
result  that  many 
cases  of active, infectious TB
can remain undetected for some time. Thus, the disease spreads from one person
to another. TB  is  spread 
when  an  infectious 
person  coughs,  sneezes, 
talks  or sings, releasing
droplets containing the bacilli  into the
air. However, TB can also be spread when TB bacilli are aerosolised by treatments,
such as  irrigating  a 
wound  that  is 
infected  with  TB, 
organ  transplants,  or bronchoscopy. In either case, a
susceptible person inhales the airborne droplets, which then traverse the upper
respiratory tract and bronchi to reach 
the  alveoli  of 
the  lungs.  Once 
in  the  alveoli, 
alveolar macrophages take up the TB bacilli, holding some in the lungs,
and transporting others throughout the body. Usually within 2-10 weeks, the
immune response limits further multiplication and spread of the bacilli.Some
patients may go on to active disease from this stage while others may be able
to contain the infection and may never develop active TB. In the patients who
contain the infection some may eliminate all the bacteria; however, in many of
the patients, the bacilli remain dormant and viable for many years, resulting
in a condition referred to as latent TB infection (LTBI). Persons with
LTBI  usually have positive TB skin tests
but have no symptoms of the disease and are not contagious . In fact, most
people who are infected with TB never go on to develop active disease and
therefore present no risk to the people around them.


Risk factors combined with TB symptoms are strong
indicators for further diagnostic workup and early detection of the disease.
Some of the main risk factors for TB include:

history of TB

contact with a known
TB case, e.g. family member or friend

compromised immunity
due to illness, e.g. HIV infection, cancer or diabetes

compromised immunity
due to medications such as steroids

migration from a
country with a high incidence of TB

history of travel to
an area with a high incidence of TB


alcohol and/or drug