Tuberculosis

Tuberculosis is a common disease that is found  almost everywhere. It is important as a cause of disability and death in many parts of the world. In developing countries such as India, you should expect a higher prevalence of tuberculosis in the under-five age group, as a result, of greater opportunities of exposure to the disease. In other words, it is likely to occur more frequently in these age group. It is estimated that there would be at least 9-10 million cases of pulmonary (lung) tuberculosis as well. 

The Disease-What  causes It? Who gets it? How and when does it spread? 

Tuberculosis is caused by Mycobacterium tuberculosis, a non-motile.  slender. acid-fast bacillus. Two  strains-human  and bovine-are  of importance to man. Human source is responsible for the vast majority of cases of India. The bacillus can be seen by examination of sputum or other secretions under a microscope after using appropriate staining procedures. 

Who gets the disease? 

Age : Tuberculosis can occur at any age.  Recent surveys in India show that it occurs more in older age groups than the younger groups. 

Sex : In India, tuberculosis is more prevalent among males over 45 years of age than among females. In females however, the peak prevalence is below 35 years. 

Socio-Economic Factors : The disease occurs more frequently in families belonging to low income groups. In Western countries a decline in death rates due to tuberculosis has occurred with an increase in standard of living.  Communities living in substandard houses which are ill ventilated and have inadequate floor space are likely to suffer more from  the disease.  Miners and textiles workers are more  prone to disease. Overcrowding as in the slum areas of the cities helps in the  rapid  spread of the disease. 

Certain social customs such as indiscriminate spitting, smoking of hukka, purdah system also help in the spread of the infection. Tuberculosis has a social stigma. This attitude leads to concealment of the disease and consequent delay in diagnosis of cases with increased risk of spreading the disease to others.

How does it spread? 

Tuberculosis is transmitted by droplets from  sputum of infected persons particularly during coughing. To carry infection, the droplet particles must be fresh to carry a viable organism  (organism that can thrive). Prolonged  household exposure to  an active tuberculosis case may lead to infection of those persons in contact with such cases. Tuberculosis is not transmitted by fomites i.e. dishes and other articles used by patient.  Sterilization of these articles is of little or no value. 

Bovine tuberculosis results from ingestion of unpasteurized milk or dairy products of tuberculous cows. 

Primarily man and in some areas also diseased cattle are the reservoir of infection of tuberculosis. 

Incubation Period : It takes about 4-12 weeks from  the time an individual is infected from an active case of tuberculosis to demonstrable primary lesion. It may take years to lead to progressive pulmonary  or extra-pulmonary tuberculosis. You should remember  that tuberculosis infection means entry or development of the organism M. tuberculosis, while  the disease has specific manifestations (symptoms and signs) resulting from the infection. 

Period of Communicability : The disease is communicable i.e.  can spread from a patient of tuberculosis to a non-infected individual, as long as tubercle bacilli are discharged by the patient. Some untreated, as in the poorer communities, or inadequately treated (discontinuing treatment) patients may  be intermittently sputum positive  for years. In other words, there is a constant danger of getting the disease from  such patients. Proper treatment generally reduces communicability within a few weeks. It only means that for control of tuberculosis, prompt and complete treatment are essential. Extra-pulmonary tuberculosis without any discharge (secretions) is not directly communicable. 

Susceptibility :  Everyone is susceptible to  the disease. However, children under  the age of 3 years are highly susceptible. In undernourished individuals susceptibility is high. Susceptibility is lowest in later childhood i.e. 4-10 years, but is again high in adolescents and young adults.