Tuberculosis is a lung disease caused by Mycobacterium tuberculosis, or Mtb, but it doesn't develop in everyone who harbors the bacteria. About 10 percent of people with Mtb go on to develop active tuberculosis, according to the National Institute of Allergy and Infectious Diseases. Over 2 billion people worldwide are infected with Mtb, and 2 million people a year die of the disease. In the United States, the bacteria infects between 10 million and 15 million people. It is transmitted through the air when an infected person coughs or sneezes.
Symptoms
People with latent Mtb infections generally don't exhibit symptoms, and can't transmit the disease to others, according to the Mayo Clinic. If the disease becomes active, it usually affects the the lungs. Signs of tuberculosis in the lungs include coughing up blood, chest pain and a cough that lasts three weeks or more. Other symptoms of tuberculosis include weight loss, loss of appetite, night sweats, chills, fever and fatigue.
Diagnosis
To diagnose tuberculosis, a doctor will perform a blood test or, more commonly, a skin test called the Mantoux test, according to the Centers for Disease Control and Prevention. In this test, a doctor injects a substance called PPD tuberculin, which causes a hard swollen area at the site of injection if the person has tuberculosis. A positive test only indicates that a person is infected with Mtb, not whether the infection is active. If the Mantoux test is positive, the doctor may order other tests to confirm the diagnosis and determine if it is full-blown tuberculosis. These can include blood tests, chest X-rays, CT scans, lab tests of mucus expelled during coughing and a genetic test called nuclear acid amplification.
Treatment
Treatment for tuberculosis involves six to 12 months of antibiotics, according to the Mayo Clinic. A latent Mtb infection only requires a single drug taken for nine months. Physicians use a combination of four antibiotics to treat active tuberculosis. To avoid building up antibiotic resistance, the patient must take the drugs exactly as directed for the entire prescribed course of treatment.
Complications
Untreated tuberculosis causes severe lung damage that can lead to death, according to the Mayo Clinic. Meningitis, joint pain and a systemic infection that affects different organs can occur. Drug resistance is a major problem in tuberculosis, because people who don't finish their entire course of treatment or who use drugs of poor quality may develop drug-resistant bacteria. Tuberculosis that is resistant to two or more of the standard drugs is called multidrug-resistant tuberculosis, and can be severe because the normal treatment will not work anymore, according to the National Institute of Allergy and Infectious Diseases.
Prevention
A vaccine called the bacille Calmette-Guérin, or BCG, is available to protect people from tuberculosis, according to the Centers for Disease Control and Prevention. In the developed world, few people receive the bacille Calmette-Guérin vaccine, but it is commonly administered to infants in Asia, Africa, Latin America, the Caribbean, Russia and Eastern Europe. In the United States, doctors and public health officials recommend the vaccine for those at high risk, such people who work with tuberculosis patients or immunocompromised individuals.
