Tuberculosis is a disease that has haunted mankind from ancient times. This disease primarily affects the lungs and is caused by the bacterium 'Mycobacterium tuberculosis'. Besides lungs, other organs such as intestines, bones, joints, skin, covering of the brain (meninges) etc can also be affected by tuberculosis. It has been more than a century since the organism causing tuberculosis got detected. In spite of having an effective treatment and a vaccine, TB still continues to be a major public health problem across the world.

Among the world nations, India reports the highest number of new tuberculosis cases every year. Signs of tuberculosis were noticed even in the bones of Egyptian mummies dated BC 2400. Ancient writings from Greece and Rome also refer to a disease with symptoms similar to tuberculosis.

In the middle ages, many people in Europe used to die of tuberculosis. Europeans of that era, firmly believed that 'royal touch' could cure tuberculosis. Patients with tuberculosis used to wait in public places for the kings of Europe and France to touch them and cure them. It is said that King Henry IV of France had touched around 1500 patients with tuberculosis at the same time. The communicable nature of tuberculosis was unknown then.

In the 18th century, tuberculosis spread to many parts of Europe. The high rate of deaths due to TB was reported among youths of Europe.

In the times of industrial revolution, when people dwelled in crowded houses with poor hygiene and poor ventilation, tuberculosis cases were quite common. It was in 1880 that Robert Koch isolated the bacterium causing tuberculosis (Mycobacterium tuberculosis). Ever since tuberculosis is also known as Koch's disease. In the 19th century, tuberculosis became highly prevalent in India also. Long term rehabilitation of tuberculosis patients with good food in well-ventilated sanatoria was the first mode of treatment. This 'Sanatorium treatment' method was used in our country also. Large mangroves or open compounds with buildings were used to rehabilitate tuberculosis patients for longer periods.

By the mid 20th century, effective medicines were developed against tuberculosis. With effective treatment, TB now has become a disease which can be completely cured in months.

How is this disease caused?

From a patient with lung tuberculosis, the bacterium, Mycobacterium tuberculosis spreads to another person. When the patient coughs, bacteria contained in the droplets of respiratory secretions or sputum reach the air. The bacteria reach the lungs of those individuals who inhale the droplets. These organisms multiply in the lungs of the recipient and disease develops later. It might take weeks, months or years for the disease to develop after the inhalation. The chances and duration to develop the disease depend mainly on the load of bacteria in the sputum, the duration, and proximity for which the two individuals were together, the immunity status of the second person, the nutritional status etc. The chances of spread of tuberculosis by sharing of personal articles or through fomites are very low as shown by various studies. The chance of spread of tuberculosis from a TB patient who took treatment correctly for at least two weeks is also very low. The TB which affects other organs other than the lungs is less likely to spread to other individuals. TB is prevalent more in males compared to females. It is also seen more in people dwelling in crowded houses with poor ventilation and poor hygiene.

Bovine tuberculosis seen in cattle is another source of tuberculosis for humans. The bacteria which causes bovine tuberculosis is Mycobacterium bovis. Very rarely bovine tuberculosis can spread to humans also. It may be due to inhalation of droplets while in close contact with the diseased cattle, from slaughterhouses or by consuming raw or unpasteurized milk.