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Tuberculosis (TB) is an infectious disease caused by bacteria called Mycobacterium tuberculosis. The bacteria usually cause an infection in the lungs, but it can affect other parts of the body such as the kidney, spine, brain, and lumph nodes. If not treated properly, TB can be fatal.
TB infection can be classified as either "latent" or "active".
A latent TB infection means a person is infected with the bacterium, but the disease does not develop and no symptoms are experienced. Latent infection occurs when the immune system of the infected person is able to keep the bacteria under control. The TB bacteria can remain dormant for years without causing the disease or symptoms. Persons with latent tuberculosis infection do not spread tuberculosis to others.
The World Health Organization states that about 10% of people who are infected with TB will become sick or infectious at some time during their life (active tuberculosis disease). People with compromised immune systems such as persons living with HIV, malnutrition, or diabetes; or people who use tobacco have a much higher risk of becoming ill.
If the immune system weakens due to another disease or medications, the TB bacteria that were dormant may become activated. Activation causes the TB disease and associated symptoms.
For some individuals, active TB disease may develop within 18-24 months of the initial infection.
The signs or symptoms of active TB infection include:
- A bad cough that lasts 2 weeks or longer
- Presence of blood or phlegm (the thick liquid that comes up from your lungs or airways) when coughing
- Pain in chest
- Loss of weight
- Loss of energy
- Poor appetite
- Fever, chills, night sweats
- Weakness or tiredness
Tuberculosis is spread from human to human through the release of droplets from the lungs or airways of an infected person. Spread can happen through coughing, sneezing, singing, playing a wind instrument, and talking (to a lesser extent). To be infected, you have to breathe in the tuberculosis bacteria. The bacteria spread through droplets in the saliva or sputum. You cannot get infected by shaking hands, sharing dishes, or sitting on toilet seats.
Persons with latent TB infection cannot transmit TB because bacteria are not present in their saliva or sputum.
When a person with active tuberculosis disease coughs, sneezes, talks, or spits, tiny droplets containing the bacteria are released into the air and can be inhaled by people who are close by. The bacteria can spread from the initial location in the lungs to other parts of the body through the bloodstream. Only a small number of bacteria are needed to cause an infection.
A skin or blood test is often used to tell if tuberculosis is present.
For a skin test, a small amount of non-infectious tuberculosis protein is injected. A positive result may occur in 2 to 3 days. If positive, the person will be tested further using tests to determine active TB such as:
- a complete medical history and examination
- chest radiography (x-rays),
- sputum smear microscopy (the sputum is examined by microscope),
- mycobacterial culture and phenotypic drug susceptibility testing (a method to determine if a person has drug resistant TB), and
- nucleic acid amplification testing (a method to determine if a particular virus or bacterium is present).
To help determine latent TB, the tuberculin skin test and interferon gamma release assay (a test of the person's immune reactivity) may be used.
TB can be treated effectively with a combination of drugs. It is important to follow the doctor's directions and take the drugs exactly as recommended. If you forget to take your pills, or if you only take some of them, the tuberculosis bacteria may become resistant to the drugs (forming a drug-resistant TB strain).
TB is largely treated without hospitalization. However, those requiring additional medical assistance may be hospitalized and stay in an airborne isolation room.
Drug-resistant TB refers to TB strains that have developed resistance towards a drug or drugs – meaning the drugs are no longer as effective. These TB strains cannot be managed by conventional treatments.
For example, multidrug-resistant TB is resistant to at least the drugs isoniazid and rifampin, two commonly used anti-TB drugs. Some strains of TB have emerged that are resistant to almost all anti-TB drugs. These are called extensively drug-resistant TB.
Please see the OSH Answers “Multi-Drug Resistant Tuberculosis (MDR-TB)” for more information.
In the workplace, employees can contract TB directly from actively infected persons or from breathing in air that contains the bacteria. While the risk of workers contracting TB is higher in health care and in prisons where people with TB may be treated or detained, all workplaces should be aware of how TB can spread. General preventative measures include education to raise awareness in workers about TB, and encouraging employees to seek medical help when TB-like symptoms are noticed.
In high risk occupations, implementing a TB control program is important. A TB control program should include policies and procedures for:
- rapid identification, isolation, and treatment of individuals with infectious TB or those suspected of being infected,
- appropriate controls such as the establishment of negative-pressure isolation rooms and a respiratory protection program, and
- adoption of routine practices and additional precautions by staff.
In a health care setting, infectious individuals should be placed in private rooms. The isolation room must be at negative air pressure and it must have adequate ventilation to dilute the concentration of contaminants within the room. The air from the isolation room must be directly exhausted to the outside. Other additional precautions such as the use of high efficiency particulate air (HEPA) filtration or ultraviolet germicidal irradiation (UVGI) may be used.
- Fact sheet last revised: 2023-02-09