Lesson 2 of 1
In Progress


September 26, 2014

Watch this CDC TB Introduction below



By the end of this module, a nurse assistant will be able to:

1. Identify a basic definition of tuberculosis.

2. Identify the way tuberculosis is spread.

3. Identify the organ that is most commonly affected by tuberculosis.

4. Identify precautions that must be used when caring for a patient with tuberculosis.




Tuberculosis, commonly known as TB, is a serious airborne bacterial infection caused by the acid-fast bacillus (AFB) Mycobacterium and can spread through the lymph nodes and bloodstream to any organ in your body. TB is spread through the air from person to person through coughs or sneezes. It usually occurs in the lungs, but it can spread to other parts of the body. Most people who are exposed to TB never develop symptoms because the bacteria can live in an inactive form in the body. But if the immune system weakens, such as in people with HIV or elderly adults, TB bacteria can become active. In their active state, TB bacteria cause the death of tissue in the organs they infect. Active TB disease can be fatal if left untreated. But the good news is; Tuberculosis is curable and preventable. 


TB is a major cause of morbidity and mortality worldwide, with over 95% of cases and 99% of deaths occurring in resource-limited settings. The human immunodeficiency virus (HIV) pandemic led to a resurgence of TB and promoted explosive nosocomial outbreaks of multiple-drug-resistant TB. The result was increased attention to TB as a global public health emergency and increased funding for TB control and research. The problems posed for TB control are compounded by increasing drug-resistant disease that is expensive to treat and may be refractory to available drugs.

World Health Organization (WHO) Key facts
  • Tuberculosis (TB) is second only to HIV/AIDS as the greatest killer worldwide due to a single infectious agent.
  • In 2012, 8.6 million people fell ill with TB and 1.3 million died from TB.
  • Over 95% of TB deaths occur in low- and middle-income countries, and it is among the top three causes of death for women aged 15 to 44.
  • In 2012, an estimated 530 000 children became ill with TB and 74 000 HIV-negative children died of TB.
  • TB is a leading killer of people living with HIV causing one-fifth of all deaths.
  • Multi-drug resistant TB (MDR-TB) is present in virtually all countries surveyed.
  • The estimated number of people falling ill with tuberculosis each year is declining, although very slowly, which means that the world is on track to achieve the Millennium Development Goal to reverse the spread of TB by 2015.
  • The TB death rate dropped 45% between 1990 and 2012.
  • An estimated 22 million lives were saved through the use of DOTS and the Stop TB Strategy recommended by WHO



TbMycobacterium tuberculosis, which causes tuberculosis (TB) disease, is a non-motile obligate aerobic bacillus (rod) that forms chains which is neither a Gram-negative nor Gram-positive rod. As an extracellular agent, Mycobacterium tuberculosis needs oxygen to live and multiply, and that is why it is attracted to the upper respiratory tract. It is also a facultative intracellular invader, allowing it to evade the immune system.  Humans serve as the only reservoir for Mycobacterium tuberculosis. It is important to note that the biggest risk factor for developing a tuberculosis infection is a compromised immune system, and the biggest risk for having the infection progress to the disease is a concurrent infection with HIV. 

TB is an ancient disease that has plagued humans for thousands of years. Evidence of TB in humans dates back to over 4,000 years ago in ancient Egyptian mummies. Egyptian mummies from 2400 BC have been found to have evidence of tuberculosis infections. Historically, TB was considered by many people to be a death sentence before treatment was discovered and was known by a variety of names including:

  • Consumption
  • Wasting disease
  • White plague



TB is spread from person to person through the air. It is not spread by contact with dirty items, soiled tissues, or by touching a patient. The germ must be inhaled. When people with lung TB cough, sneeze, or spit, they propel the TB germs into the air.  When an infected person talks, coughs, or sneezes, small infected particles (1 to 5 micrometers per diameter) enter the air. Larger droplets fall, but the small particles remain suspended in the air and can be inhaled by anyone who comes in contact with them. A person needs to inhale only a few of these germs to become infected. About one-third of the world’s population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with the disease and cannot transmit the disease.

When transmission takes place and the bacterium is inhaled, the bacilli then travel through the airways to the lungs and the alveoli, where they begin to multiply. The bacilli invade the lymph symptom and can also travel to other parts of the body, including the upper lobes of the lungs. The host’s immune system attempts to control the spread of M. tuberculosis by an inflammatory reaction in which some bacilli are engulfed by phagocytes (neutrophils and macrophages) and TB-specific lymphocytes destroy the bacilli, along with normal tissue which causes scarring seen on Chest Xray of infected patients. As cells are destroyed, exudate begins to accumulate in the alveoli and causes bronchopneumonia, usually within 2 to 10 weeks after initial exposure.

Here is a disturbing story of how a Nurse Assistant unknowingly exposed many infants to Tuberculosis in a hospital Texas Nurse Assistant Exposes Hundreds of Infants to Tuberculosis in a Year with five babies turning up positive for TB exposure.


Latent TB Infection (LTBI) Versus Active TB Disease

LTBI refers to someone who has bacteria present in his or her body but is not ill with signs or symptoms of the disease. The only sign is a positive TB skin test or scar on the chest X-ray.  This occurs when the host’s immune system is adequate, and the macrophages wall off the mass of live and dead bacilli, forming a granuloma and therefore causing a positive skin reaction (cell-mediated immune response) but with no active infection. According to WHO, about one-third of the world’s population has latent TB. People with latent TB have no symptoms and cannot spread the disease to others while the disease remains dormant. Chest x-rays and sputum tests are generally negative, but these patients are at risk of active TB and need treatment to prevent TB disease. 

Active TB

If the immune system is overwhelmed because of a large number of bacilli or a weak immune system, then the bacilli begin to multiply and destroy tissue, resulting in active TB and sometimes causing a cavity to form in the lungs. Only about 10% of those with an initial infection develop active disease. Additionally, dormant bacilli may also become reactivated, sometimes years after the initial infection making these patients infectious with active TB disease. In other words, someone can get active TB when the bacteria that cause the disease overcomes the body’s immune system. This can happen right away after exposure but for others, this may develop later if the immune system gets weak. It is important to note that when someone has active TB, he is now contagious and can spread the disease to others.


Signs and symptoms of active TB disease include;

  • Fatigue and malaise
  • Fever or low-grade fever
  • Night sweats or chills
  • Unexplained weight loss
  • Loss of appetite
  • Pleuritic chest pains especially with cough
  • A persistent cough (pulmonary infection)
  • Blood-tinged sputum (pulmonary infection)
  • Hemoptysis



In the early 1990s, people caring for patients with tuberculosis began to notice that there was a growing percentage of cases that did not respond to traditional drug treatment therapy. They were facing a new problem, a drug-resistant strain of Tuberculosis. Drug-resistant tuberculosis has been a growing problem since that time. There are two types of drug-resistant tuberculosis; 

  • Multi-drug-resistant tuberculosis: The bacteria that cause this form of the disease cannot be killed by the two most powerful drugs available, isoniazid and rifampin. This type of tuberculosis can still be treated. However the treatment protocol is long (two years), the drugs that are effective are expensive, and they have serious, unpleasant side effects.
  • Extensive drug-resistant tuberculosis: Fortunately, this type of tuberculosis is uncommon and only 49 cases were been reported in the United States between 1993 and 2006 and most likely found in patients who are foreign-born or immuno-compromised (such as those with HIV/AIDS). This type of resistant TB is very difficult to treat. None of the standard medications work, and the second-line drugs that can help someone with multi-drug-resistant tuberculosis do not work, either. Like multi-drug-resistant tuberculosis, treating extensive drug-resistant tuberculosis is a lengthy process with serious, unpleasant side effects. Active TB requires treatment for extended periods of time, usually 18-24 months, with multiple drugs, and some people cannot or will not comply with this regimen. In rare cases, people with resistant TB strains have required forced hospitalization and isolation to protect the general public.

The primary causes for increased resistance include;

  1. Failure to complete a course of treatment
  2. Mismanaged treatment, including incorrect medication, dosage, or duration of therapy.



Disseminated tuberculosis (TB) is a contagious bacterial infection in which TB bacteria has spread from the lungs to other parts of the body through the blood or lymph system. It is also sometimes referred to as miliary TB. Disseminated TB develops in a small number of infected people whose immune systems do not successfully contain the primary infection. It can occur within weeks of the primary infection but sometimes, it does not occur until years after the primary infection.  Patients who have a weakened immune system due to diseases (such as AIDS) are the ones likely to get this disease. Infants and the elderly are also at increased risk because their immune systems are less effective. Symptoms of extrapulmonary (disseminated) TB involve multiple organs.


Bacille Calmette-Guérin (BCG) Vaccine

While a vaccine is available for TB, it is not routinely recommended for use in the United States. BCG (Bacille Calmette-Guérin) is a tuberculosis vaccine that is commonly administered to children in countries with high incidences of childhood tuberculous, meningitis, and disseminated TB. BCG has been used for about 80 years, but it has limitations. BCG has proven to be about 80% effective in preventing TB infection, but the results last only about 15 years, and effectiveness appears to vary according to the environment, so it is more effective in some parts of the world than in others. BCG does not prevent primary infection or reactivation of latent pulmonary infection.

BCG is not recommended in the United States because infection with Mycobacterium tuberculosis has a low incidence, BCG is not always effective to prevent adult pulmonary TB, and adult immunization is variable. Furthermore, BCG often results in false positives on skin testing, making a subsequent diagnosis of TB more difficult. Immigrants or visitors from other countries may have been vaccinated as infants or children, so those showing positive skin testing should be questioned carefully about previous vaccination before treatment is prescribed since skin testing is not reliable for this population. Blood tests are more accurate and are less likely to render a false positive