Health Hygiene & Sanitation

Lesson 36 : Prevention Of Respiratory Infections


Tuberculosis is a specific infectious disease caused by M. tuberculosis. The disease primarily affects lungs and causes pulmonary tuberculosis. It can also affect intestine, meninges, bones and joints, lymph glands, skin and other tissues of the body. The disease is usually chronic with varying clinical manifestations.

Agent Factors:

  1. Agent: M. tuberculosis is a facultative intracellular parasite; Non-specific infections have been reported to be widely prevalent in the southern part of India.

  2. Source of Infection: There are two sources of infection- human and bovine.

    1. Human source: Human being infected with tubercle bacilli and not received any treatment nor treated fully will serve as the most common source of infection.

    2. Bovine source: The bovine source of infection is usually infected milk. Bovine tuberculosis is not a problem in India because of the practice of boiling milk before consumption.

  3. Communicability: Patients are infective as long as they remain untreated.

Host Factors:

  • Age and Sex: It affects all ages, males are more affected than females.

  • Heridity: though it is not a hereditary disease, twin studies indicate that inherited susceptibility is an important risk factor.

  • Nutrition: Malnutrition is widely believed to predispose to tuberculosis

  • Immunity: Man has no inherited immunity against tuberculosis. It is acquired as a result of natural infection or BCG vaccination.

Social Factors:

Tuberculosis is a social disease with medical aspects. It has also been described as a barometer of social welfare. The social factors include poor quality of life, poor housing, overcrowding, population explosion, under nutrition, lack of education, large families, early marriages, lack of awareness of causes of illness etc. All these factors are interrelated and contribute to the occurrence and spread of tuberculosis.

Mode of Transmission:

Tuberculosis is transmitted mainly by droplet infection and droplet nuclei generated by sputum of positive patients with pulmonary tuberculosis. Droplets are generated by coughing. Tuberculosis is transmitted by fomites, such as dishes and other articles used by the patients.

Incubation Period:

The incubation period ranges from 3-6 weeks. The development of disease depends on closeness of contact, extent of disease, extent of infection and host-parasite relation.


Tuberculosis control means reduction in the prevalence and incidence of disease in the community. According to WHO “tuberculosis control" is said to be achieved when the prevalence of natural infection in the age group of 0-14 years is 1 per cent. Case finding and treatment (curative) and BCG vaccination (preventive) are the components of National Tuberculosis Programme. Directly Observed Treatment, Short Course (DOTS), is the strategy for cure.

Last modified: Thursday, 26 April 2012, 12:55 PM