The bacteria species Mycobacteria tuberculosis causes mycobacterial lung disease, which is most well known as tuberculosis, explains Kenyon College. Around 30 percent of the human population carries these bacteria, and about 10 percent of carriers become sick each year. The disease is airborne and is spread from person to person.
Tuberculosis is most dangerous to people with lowered immune systems, according to Mayo Clinic. Immune systems are sometimes weakened by other diseases, such as HIV, advanced kidney disease, cancer or diabetes. Poor nutrition, chemotherapy, drugs that prevent rejection of transplants, drugs that treat autoimmune disorders, very young or very old age can also decrease the immune system's effectiveness. Tuberculosis is also more common in certain regions such as sub-Saharan Africa, China, India, Pakistan and Russia. Use of certain drugs, including alcohol or tobacco, increases the risk of developing tuberculosis as well.
Tuberculosis is very dangerous if left untreated, Mayo Clinic says. Many strains are resistant to the drugs commonly used to treat the disease, but there are alternate treatment regimens available when drug resistant strains are discovered. All the treatments for tuberculosis are dangerous, however, as they are very hard on the liver. People being treated for tuberculosis must also monitor themselves for symptoms of liver damage.