Tuberculosis Background Information



Tuberculosis Background Information

Definition

Tuberculosis (TB) is a potentially serious infectious disease that primarily affects your lungs. Tuberculosis is spread from person to person through tiny droplets released into the air. Most people who become infected with the bacteria that cause tuberculosis don't develop symptoms of the disease.

Despite advances in treatment, TB remains a major cause of illness and death worldwide, especially in Africa and Asia. Every year tuberculosis kills almost 2 million people. Since the 1980s, rates of TB have increased, fueled by the HIV/AIDS epidemic and the emergence of drug-resistant strains of the TB bacteria.

Most cases of tuberculosis can be cured by taking a combination of medications for several months or longer. It's important to complete your whole course of therapy.

Symptoms

Although your body may harbor the bacteria that cause tuberculosis, your immune system often 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.

• Active TB. This condition makes you sick and can spread to others.

Signs and symptoms of active TB include:

• Unexplained weight loss

• Fatigue

• Fever

• Night sweats

• Chills

• Loss of appetite

Tuberculosis usually attacks your lungs. Signs and symptoms of TB of the lungs include:

• Coughing that lasts three or more weeks

• Coughing up blood

• Chest pain, or pain with breathing or coughing

Tuberculosis can also affect other parts of your body, including your kidneys, spine or brain. When TB occurs outside your lungs, symptoms vary according to the organs involved. For example, tuberculosis of the spine may give you back pain, and tuberculosis in your kidneys might cause blood in your urine.

TB infection vs. active TB

If you breathe TB bacteria into your lungs, one of four things might happen:

• You don't become infected with TB. Your immune system immediately destroys the germs and clears them from your body.

• You develop latent TB infection. The germs settle in your lungs and begin to multiply. Within several weeks, however, your immune system successfully "walls off" the bacteria in your lungs, much like a scab forming over a wound. The bacteria may remain within these walls for years — alive, but in a dormant state. In this case, you're considered to have TB infection and you'll test positive on a TB skin test. But you won't have symptoms and won't transmit the disease to others.

• You develop active TB. If your immune defenses fail, TB bacteria begin to exploit your immune system cells for their own survival. The bacteria move into the airways in your lungs, causing large air spaces (cavities) to form. Filled with oxygen — which the bacteria need to survive — the air spaces make an ideal breeding ground for the bacteria. The bacteria may then spread from the cavities to the rest of your lungs as well as to other parts of your body.

If you have active TB, you're likely to feel sick. Even if you don't feel sick, you can still infect others. Without treatment, many people with active TB die. Those who survive may develop long-term symptoms, such as chest pain and a cough with bloody sputum, or they may recover and go into remission.

• You develop active TB years after the initial infection. After you've had latent TB for years, the walled-off bacteria may suddenly begin multiplying again, causing active TB, also known as reactivation TB. It's not always clear what triggers this reactivation, but it most commonly happens after your immune system becomes weakened. Your resistance may be lower because of aging, drug or alcohol abuse, malnutrition, chemotherapy, prolonged use of prescription medications such as corticosteroids or TNF inhibitors, and diseases such as HIV/AIDS.

Only about one in 10 people who have TB infection goes on to develop active TB. The risk is greatest in the first two years after infection and is much higher if you have HIV infection.

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. Tuberculosis and HIV have a deadly relationship — each drives the progress of the other.

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.

TB is one of the leading causes of death among people with AIDS, especially outside the United States.  One of the first indications of HIV infection may be the sudden onset of TB, often in a site outside the lungs.

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