Tuberculosis is transmitted by respiratory way; an infected person will emit while coughing or sneezing about 2-3 bacterial particles. The person in immediate proximity will inhale the particles that will get to the lungs and multiply causing the infection.
Another less common transmission type is through the skin in laboratory workers and pathologists. They contact Mycobacterium through skin injuries while handling infected tissues. Cases of Tuberculin infection have been found also in circumcisions made with unsterilised instruments or in people with tattoos given in unhygienic environments.
In spite of the high risk of catching the Tuberculosis bacteria, the actual disease is only developed by 5-10% of the persons with primo infection. Healthy immune systems manage to annihilate the bacterial strains completely.
Most cases of actual Tuberculin infection are seen in smokers, persons of the lower society living in poverty and misery, alcoholics and people with depressed immune systems. The patients really developing the infection might go through two important stages of the disease, the primary and the secondary stage.
The primer stage of Tuberculosis or primo infection doesn’t show clinical signs of the disease and the patient is frequently unaware of his condition. The disease is not contagious in the primer stage and cannot cause further cases of Tuberculosis infection.
If the immune system is working, immune cells like the macrophages detect and ingest the infectious particles transporting them to the lymph nodes where they can be destroyed. In some cases, the bacterial fragments get to the lymph nodes and multiply causing the ganglion Tuberculosis.
If the bacteria is not destroyed and annihilated, the infectious the fire box activates producing the appearance of clinical signs of Tuberculosis. The patient coughs, sweats mostly at night, looses weight and develops fever. In case of an X-ray investigation opacities of the lungs and fluids collection (Pleurisy) can be discovered.
If the bacteria are only inhibited, not killed, the immune cells form a wall around the inactivated germs producing a so called Granulom. The wall collects amounts of calcium in time forming the Ghon focus. Usually the tubercles heal and permanent scars remain visible on the chest X-rays. The bacteria remain dormant inside the cell wall until the immune system is weakened by different factors and the bacteria are released. The primer infection can evolve into a secondary one.
The secondary Tuberculosis develops when the bacterial fragments multiply and begin to destroy the surrounding tissues inside the lungs. The infection might also advance to other organs or tissues by sanguine way. Other focus and tubercles develop inside the lungs and fluid collection can occur between the linings of the lungs. Patients in secondary stage cough blood and are contagious for people in the proximity.