The bacteria Mycobacterium tuberculosis causes tuberculosis, or TB. It spreads when actively infected patients cough disease-filled sputum into the air, and others breathe it in. Untreated tuberculosis can cause serious lung or organ damage or even death. Fortunately, the vast majority cases of tuberculosis can be cured if patients complete months of treatment with a combination of medications, according to MayoClinic.com.
Latent Infection
When people are infected with tuberculosis, but show no signs of the disease, it is called a latent infection. Latent live tuberculosis virus survives in the body, but is held in check by the immune system, and the infected person is not even contagious. If the immune system weakens, the infection can activate years later. The Merck Manual states that about one-third of all the people in the world carry tuberculosis, but only about 15 million cases are active at any one time.
Active Infection
According to the Merck Manual, only 10 percent of healthy patients develop active tuberculosis after exposure. Activation most often occurs in the lungs, but can also affect other sites. During active infection, the patient is contagious until at least two weeks of treatment have passed, explains MayoClinic.com. With active tuberculosis in the lungs, the patient often shows no specific symptoms. Weight loss, fatigue, and generally feeling unwell are the most common signs. Some people develop a cough with yellow or green sputum. People cough blood only when the virus eats cavities into the lungs.
Lung Damage
A delayed, damaging over-reaction of the immune system to the presence of the tuberculosis virus produces balls of immune cells surrounding dead lung tissue. The lesions can eat into the walls of the lungs. Large lesions that burst into the air space of the lungs cause an accumulation of pus called empyema. Excess fluid can also collect in the lungs, compromising breathing. Lung damage can be life threatening if a lung collapses or if a lesion eats into the pulmonary artery.
Damage to Other Sites
When tuberculosis spreads to other parts of the body, which is a rare occurrence, the symptoms vary according to the affected organs. Tuberculosis can damage the kidneys, abdomen, pericardium, or covering of the heart, bones and joints, lymph nodes, meninges, coverings of the brain and spinal cords; gastrointestinal tract, liver, skin, or the whole body, which is known as miliary tuberculosis. Tuberculosis of the meninges is the most serious form of the disease, according to the Merck Manual, because of the high risk of death. In parts of the world where tuberculosis is common, TB pericarditis is a common cause of heart failure. TB in the bones causes arthritis and TB in the spine can collapse the vertebrae and compress the spinal cord.
Death
Tuberculosis can be fatal without appropriate treatment. According to 2009 information from MayoClinic.com, tuberculosis kills about 2 million people every year. It is still a major cause of death in Asia and Africa.
