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What is Tuberculosis (TB)?
TB is a serious infectious disease caused by the mycobacterium tuberculosis (tubercle bacillus) bacterium. Approximately one third of the world population is infected with TB. But TB infection rates are very low in the United States. It most commonly affects the lungs. The bacteria can infect the larynx, spine, kidneys, and other parts of the body. Pulmonary TB (infections of the lung) is most common. In the lungs it destroys elastic lung tissue, which is replaced with fibrous connective tissue.
How is it Transmitted?
TB is spread by airborne transmission. The tuberculosis bacilli travel in minute droplets of fluid called droplet nuclei. When a person with active TB sneezes, coughs, sings, talks, shouts, or breathes, these droplet nuclei are projected into the air where they become suspended. When another person inhales this contaminated air, they can become infected with the bacteria.
What are the Symptoms?
When a person is infected with the bacteria and there are no symptoms, the condition is called latent tuberculosis infection or LTBI. Persons with LTBI are not able to spread the infection to others, but, unless treated, the bacteria may become active at anytime. General symptoms of active tuberculosis are fatigue, weight loss, fever, chills, night sweats. Symptoms of pulmonary TB include persistent cough, chest pain and coughing up blood. Other symptoms are dependent on location and may include back pain, blood in urine.
How is it Diagnosed?
Tuberculosis infection is usually diagnosed through the use of the mantoux tuberculin skin test (PPD). In this test a dose of purified protein derived from the tubercle bacilli, which is non-infectious, is injected into the upper layer of skin, usually on the forearm. After 48-72 hours, the test site is examined. There may be some redness and a hardened area of tissue (induration) which will be evaluated. A positive skin test indicates infection with tuberculosis, but is not necessarily an indication of active tuberculosis. Chest x-rays and sputum smears and cultures are used to test for active tuberculosis.
Can it be Treated?
Yes, TB can be treated.
LTBI: After transmission of the tuberculi bacilli, if antibiotic treatment is given for 9-12 months, the chances of a person developing active tuberculosis is very small. Usually within 2-10 weeks after initial infection, the body's immune response limits further growth and spread of the tuberculi bacilli; however, some may remain dormant for many years. Persons with LTBI usually have a positive tuberculin skin test (TST), but they do not have symptoms of active TB, and they are not infectious. Persons with LTBI have an approximately 10% chance of developing active TB during their lifetime. This risk is greatest during the first two years after infection. Immunocompromised persons have a greater risk for latent TB to progress to active TB.
Active TB: Can be effectively treated with antibiotics. Drug treatment may be required for nine months up to two years, depending on the strain of bacteria. Some drug resistant tuberculosis may require a combination of several antibiotics. It is extremely important for a person with active TB to take their medications as prescribed and for the length of time required to cure the infection.
Who is at Risk?
High risk groups are the homeless, the elderly, prison inmates, alcoholics, IV drug users, persons with HIV/AIDS, African-Americans, Asians, American Indians, Hispanics, and foreign-born people who come from a region with a high rate of TB (i.e. Asia, Africa, Carribean, and Latin America). Healthcare workers in general are considered to be at increased risk. Many factors however are considered in determining the risk for each healthcare facility. These include: the amount of TB in the community served, the type of facility, outpatient vs inpatient services, the number of patients diagnosed with TB, the drug-susceptibility patterns of patients treated for TB, the PPD skin test results of the healthcare workers, and the infection control policies practiced.