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TB Basics

Tuberculosis (also known as "TB") is a disease caused by a type of bacteria called Mycobacterium tuberculosis. TB mainly infects the lungs, although it can also affect other organs.

When someone with untreated TB coughs or sneezes, the air is filled with droplets containing the bacteria. Inhaling these infected droplets is the usual way a person gets TB.

One of the worst diseases of the 19th century, TB was the eighth leading cause of death in children 1 to 4 years of age in the 1920s. As the general standard of living and medical care got better in the United States, the incidence of TB decreased. By the 1960s, it wasn't even in the top 10 causes of death among kids of any age group.

But TB is making a comeback in the United States today — particularly among the homeless, those in prison, and people whose immune systems have been weakened because of HIV infection.

Signs and Symptoms

In older infants and children, the first infection with the tuberculosis bacteria latent tuberculosis infection (LTBI) usually produces no signs or symptoms, and a chest X-ray shows no signs of infection. A person with a positive tuberculin test (PPD), even if they show no disease, will usually need to receive medication.

A primary infection usually resolves on its own when a child develops immunity over a 6- to 10-week period. But in some cases, TB can progress and spread all over the lungs (called progressive tuberculosis) or to other organs. This causes signs and symptoms like fever, weight loss, fatigue, loss of appetite, and cough.

Another type of infection is called reactivation tuberculosis. Here, the primary infection has resolved, but the bacteria are dormant, or hibernating. When conditions become favorable (for instance, a lowered immunity), the bacteria become active. Tuberculosis in older children and adults may be of this type.

The most prominent symptom is a persistent fever, with sweating during the night. Fatigue and weight loss may follow. If the disease progresses and cavities form in the lungs, the person may experience coughing and the production of saliva, mucus, or phlegm that may contain blood.


Tuberculosis is contagious when it's airborne and can be inhaled by others. The incubation period (the time it takes for a person to become infected after being exposed) varies from weeks to years, depending on the individual and whether the infection is primary, progressive, or reactivation TB.


Preventing TB depends on:

New cases and potentially contagious patients are identified through proper use and interpretation of the tuberculin skin test.

A vaccine called BCG (Bacille Calmette-Guérin) is considered controversial because it isn't very effective in countries with a low incidence of TB, such as the United States. However, it may be considered for people moving to countries where TB is common.


A doctor may recommend hospitalization for the initial evaluation and treatment of TB, especially if:

However, most people with tuberculosis can be treated as outpatients and cared for at home. The treatment is usually in the form of oral medications. In some cases, three or four drugs may be prescribed.

Even though treatment may require months to complete, it's very important that the full course of medicine be taken in order for tuberculosis to be cured.


Tuberculosis is a chronic disease that can persist for years if it isn't treated.

When to Call the Doctor

Call the doctor if you:

Reviewed by: Nicole A. Green, MD
Date reviewed: January 2014

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
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