does not produce noticeable symptoms. During this early stage, TB is not highly contagious and does not produce noticeable symptoms. Macrophages (cells that detect and destroy foreign matter) ingest the bacteria and transport them to the lymph nodes where they may be inhibited, destroyed, or they may be multiplied. .
If the bacteria are multiplied, active primary tuberculosis will develop. Symptoms include coughing, night sweats, weight loss, and fever. A chest X-ray may show shadows in the lungs or fluid collection between the lungs and its lining. If the bacteria are inhibited, rather than destroyed, the immune cells and the bacteria form a mass known as a tubercle. In effect, the immune cells form a wall around the inactive bacteria. As long as the immune system remains strong, the TB bacteria will remain walled off and inactive. These initial tubercles in the lungs usually heal, leaving permanent scars that appear as shadows in the chest X-rays. At this initial stage, the disease does not progress, but the bacteria may remain dormant in the body for many years. If the immune system becomes weakened, the tubercle opens, releasing the bacteria and the infection may develop into secondary TB.
In Secondary TB, the formerly dormant bacteria multiply and destroy tissues in the lungs. They also may spread to the rest of the body via the bloodstream. Fluid or air may collect between the lungs and the lining, while tubercles continue to develop, progressively destroying lung tissue. Coughing of blood or phlegm may occur. At this secondary stage, carriers of TB can infect others.
Diagnosis of TB requires several methods. The chief methods are skin tests, chest X-rays and laboratory tests. Skin tests can determine if a person has been infected with the tubercle bacilli in the past. However, such tests do not tell the physician whether the active disease is present. All types of skin tests are based on specific allergic reactions to the tubercle bacilli.
