Tuberculosis is an infectious disease that usually affects the lungs. Compared with other diseases caused by a single infectious agent, tuberculosis is the second biggest killer, globally.
Although your body may harbor the bacteria that cause tuberculosis (TB), your immune system usually can prevent you from becoming sick. For this reason, doctors make a distinction between:
Latent TB. In this condition, you have a TB infection, but the bacteria remain in your body in an inactive state and cause no symptoms. Latent TB, also called inactive TB or TB infection, isn't contagious. It can turn into active TB, so treatment is important for the person with latent TB and to help control the spread of TB. An estimated 2 billion people have latent TB.
Active TB. This condition makes you sick and in most cases can spread to others. It can occur in the first few weeks after infection with the TB bacteria, or it might occur years later.
Signs and symptoms of active TB include:
Tuberculosis is caused by bacteria that spread from person to person through microscopic droplets released into the air. This can happen when someone with the untreated, active form of tuberculosis coughs, speaks, sneezes, spits, laughs or sings.
HIV and TB
Since the 1980s, the number of cases of tuberculosis has increased dramatically because of the spread of HIV, the virus that causes AIDS. Infection with HIV suppresses the immune system, making it difficult for the body to control TB bacteria. As a result, people with HIV are many times more likely to get TB and to progress from latent to active disease than are people who aren't HIV positive.
How do you know if you have TB?
Your doctor can use a purified protein derivative (PPD) skin test to determine if you’re infected with the TB bacteria.
You doctor can use a blood test to follow up on TB skin results.
If your skin test or blood test is positive, you will likely be sent for a chest X-ray, which looks for certain small spots in your lungs. These spots are a sign of TB infection and indicate that your body is trying to isolate the TB bacteria. If your chest X-ray is negative, you likely have latent TB. It is also possible your test results were incorrect and other testing may be necessary. If the test indicates you have active TB disease, you will begin treatment for active TB. Otherwise, you will likely need to be treated for latent TB to prevent the bacteria from reactivating and making you and others sick in the future.
Your doctor may also order tests on your sputum or mucus, extracted from deep inside your lungs, to check for TB bacteria. If your sputum tests positive, this means you can infect others with the TB bacteria and should wear a special mask until after you’ve started treatment and your sputum tests negative for TB.
Other tests such as a CT scan of the chest, bronchoscopy, or lung biopsies may be required if other test results remain unclear.
How is tuberculosis treated?
Many bacterial infections are treated with antibiotics for a week or two, but TB is different. People diagnosed with active TB disease generally have to take a combination of medications for six to nine months. The full treatment course must be completed. Otherwise, it’s highly likely a TB infection could come back. If TB does recur, it may be resistant to previous medications and be much more difficult to treat.