Tuberculosis remains one of the most common health problem despite preventive and control measures that have been taken in past few decades (1). Pakistan, with 179.5 million people (2) is ranked fifth country among 22 that were extremely burdened by TB and 63% cases were from Mediterranean regions.
TB is responsible for almost 8.8 million cases and 1.4 million deaths around worldwide (3).
According to Gerstman, epidemiological triangle of TB showed an agent is insufficient to cause disease singly. Even it can survives harmlessly in human body. Other two angles host and enivornment involved in proper causation. Tuberculosis is caused by interplay of environmental and genetic factors which can be explained in the form of an epidemiological triad:
Agent for the casing TB is Mycobacterium tuberculosis, which is an acid-fast, gram-positive, aerobic, non-motile, rod-shaped organism. Two of its forms cause disease in humans: Human variety and the Bovine variety.
Man is the host for TB. Host factors that makes him susceptible for the disease are as follows:
Infants and children are not only more susceptible to develop TB than adults, but also suffer from the severe form of the disease e.g. Miliary tuberculosis (4). This is mainly because of their immunologic immaturity (4). Though no age is immune from TB. In Pakistan, more than 75% of active TB cases belong to the productive age group (15-59 yrs).
The incidence of TB is high in males as compared to females in all age groups except childhood, when incidence is higher in females (5).
Some people resist TB more effectively than others. This maybe explained in part by the genetic factors related to TB (6) HLA – DR 2 has been associated with the susceptibility to TB in Asian population (6).
Malnutrition increases morbidity due to TB as well as its mortality, especially in resource poor settings. Poor nutrition affects the immune system and thus predisposes a person to tuberculosis (7).
Lesser the education, higher is the TB prevalence. In one study it was found that in urban areas that people with no schooling suffer from TB four times than those who have tertiary level education (8).
Working in overcrowded and ill-ventilated places increases its chances of spreading. Some occupational diseases like silicosis and anthracosis increases the susceptibility to TB (9).
Certain environmental factors prone a person to TB. These may include
Overcrowding leads to poor hygienic conditions, poor ventilation and contact of infectious case with more people increasing the chances of transmission of TB.
The association between TB and poverty is well established. Poverty can increase person’s vulnerability to TB. Crowding, malnutrition, poor air ventilation and poor sanitation all are related to poverty and have been associated with increased probability of being infected with TB as well as activation of the infection (10).