Tuberculosis is an infectious disease that is responsible for over one million deaths every year worldwide, and is caused mainly by the bacterium Mycobacterium tuberculosis, also called the ‘tubercle bacilli’. It usually infects the lungs and causes damage, but can spread to other parts of the body as well. It is transmitted through the air (airborne) and can infect a healthy person who inhales droplets containing the tubercle bacilli from the cough or sneeze of an infected individual.
Once inside the person’s body, it travels through the respiratory tract to reach the alveoli of the lungs, where it gets attacked by some cells of the immune system. While most of the bacteria are destroyed, some of them are able to survive intracellularly and multiply. Eventually, the immune system responds and numerous white blood cells gather at the site of infection, forming a barrier around the bacteria called a ‘granuloma’ to prevent them from spreading.
If the barrier formed by the immune cells is able to keep the tubercle bacilli under control, the infection will not spread and the bacteria will be trapped within the granuloma. This results in what is called a Latent Tuberculosis Infection (LTBI). Because the infection cannot spread, there will be no damage or symptoms, the person is not infectious, and thus it is not considered a case of tuberculosis.
On the other hand, if the bacteria are not successfully contained by the immune system, the infection will spread to other parts of the Lungs, as well as other organs of the body through the bloodstream, resulting in a full-blown tuberculosis disease. At this point, symptoms begin to manifest and the person becomes capable of infecting other people.
Note that if one has a latent tuberculosis infection, they can develop TB disease later on. The risk is higher in those with a weakened immune system, such as HIV positive individuals, and children below 5 years of age because their immune system is still developing.
The most common symptoms of tuberculosis include persistent coughs with thick phlegm or blood lasting three weeks or more, chest pain, fever, weakness, night sweats, appetite and weight loss, and the development of swollen lymph nodes in the neck as the disease progresses. Some of the symptoms depend on the site of infection. For example, if the Brain and Spinal cord are infected, the condition is called Tuberculous meningitis, and the individual will experience dizziness, headaches and neck stiffness.
There are various methods for the diagnosis of tuberculosis disease. Tests like the Tuberculin skin test and a blood test are used to detect if a person has been exposed to tuberculosis infection. These tests cannot differentiate between a latent infection (LTBI) and an active tuberculosis disease (TB), thus more tests like Radiography scans and culturing of sputum samples (phlegm from deep within the throat) are used to confirm the disease.
Tuberculosis can be treated by special drugs called antibiotics, but the treatment takes months to complete and could be expensive, depending on how serious the disease is.
The most effective way of preventing the disease is by vaccination with a special vaccine called ‘BCG Vaccine’, which will help protect the individual from future infections. As the disease is airborne, it is difficult to effectively prevent people from getting infected. Thus, it is important that people are aware of the symptoms of the disease, and individuals suspected of having the disease should be tested immediately to avoid spreading the infection to others.
Also, those on tuberculosis treatment should ensure they strictly adhere to it to prevent the bacteria from developing resistance to the drugs.