Tuberculosis

In this lesson, we'll be looking deeper into tuberculosis (TB). We'll examine what the disease is, the two TB-related conditions, who is most at risk, the incidence rate in the U.S., how it's transmitted, and the treatment options and preventative measures people most at risk can take.

TB is caused by a bacterium appropriately called mycobacterium tuberculosis. The bacteria usually attack the lungs, but it can also attack any part of the body including the kidneys, brain, and spine.

TB is one of the world's deadliest diseases (though not in the U.S.), and while very contagious, it's also curable and preventable.

TB-Related Conditions

There are two TB-related conditions:

1. Latent TB Infection (LTBI)

LTBI is present when an infected person has the TB germs in the body but isn't sick due to the germs not being active. There are usually no symptoms of TB disease and that person cannot spread the disease to others.

However, that same person could still develop TB disease in the future. Often, treatment is given to prevent the person from developing TB disease.

2. TB Disease

TB disease is present when the TB germs are active. In these situations, the germs multiply and destroy tissue in the body. Symptoms are usually present.

People with TB disease in the lungs and throat can spread the TB germs to others and are also prescribed treatment, usually drugs.

Who is Most at Risk?

There are two groups of people most at risk of getting TB.

1. People recently infected with TB bacteria

People who have come in close contact with a person infected with the TB bacteria, people who have immigrated from high-rate areas around the world, and children under the age of five who have tested positive for the TB bacteria are most at risk.

People with high rates of TB transmission include:

• Homeless people
• Injection drug users
• People who have HIV
• People working in or living in places where there are high-risk individuals:
  • Hospitals
  • Homeless shelters
  • Correctional facilities
  • Nursing homes
  • Residential homes for people with HIV

2. People with medical conditions that weaken the immune system

Those with weakened immune systems are particularly vulnerable, and this includes babies and younger children. Others who typically have weakened immune systems include:

• People who have HIV
• Substance abusers
• People with silicosis
• People with severe kidney disease
• People with low bodyweight
• People with diabetes mellitus
• Organ transplant recipients
• People with head or neck cancer
• People on corticosteroids
• People receiving specialized treatments for rheumatoid arthritis and Crohn's disease

Incidence Rates in the U.S.

Incidence rates of TB in the U.S. are low. In 2016, there were only a total of 9272 TB cases reported, which represents a decrease of 2.9 percent from 2015. The national incidence rate is 2.9 cases per 100,000 people, which also represents a decrease from 2015 of 3.6 percent.

How is TB Transmitted?

The TB bacteria is spread by airborne transmission, meaning through the air from one person to another. The bacteria are put into the air when a person with TB in the lungs and throat cough, speak, or sing.

People in the vicinity then breathe in that bacteria and become infected. The bacteria settle in the lungs and begin to grow. They can then move through the blood to other parts of the body, namely the kidneys, brain, and spine.

Signs and Symptoms of TB

TB symptoms depend on where in the body the TB bacteria are growing. Usually, TB grows in the lungs (pulmonary TB) and this can cause:

• Bad cough lasting three or more weeks
• Pain in the chest
• Coughing up blood or phlegm

Other more general symptoms can also include:

• Weakness or fatigue
• Weight loss
• Loss of appetite
• Chills
• Fever
• Night sweats

TB Testing and Diagnosis

There are two kinds of tests to detect the TB bacteria in the body.

1. TB Skin Test

The Mantoux tuberculin skin test (TST) is performed by injecting a small amount of fluid called tuberculin into the skin on a person's arm. That person then must return 48 to 72 hours later to have a healthcare provider check for their reaction.

The diagnosis depends on the size of the raised, hard area or swelling on the arm that results from the injection. It should be noted that this is the preferred TB test for children under five years of age.

2. TB Blood Test

The TB blood test, also called Interferon-gamma release assay or IGRA, is done when a healthcare provider draws blood from a person suspected of having TB and sends it to the lab for analysis and results.

Regardless of which test is done, a positive test is a sign that the person tested is infected with the TB bacteria and additional tests must be done to see if it's a latent TB infection or TB disease

A negative test is a sign that the person's body did not react to the testing and neither latent TB infection nor TB disease are likely.

TB Treatment Options

There are 10 drugs currently approved by the FDA for treating TB. In addition, the CDC offers a guide for a basic treatment schedule.

TB Prevention Techniques

There is a TB vaccine known as the Bacille Calmette-Guerin vaccine. It's used in many countries that have high rates of infection to prevent childhood TB and also meningitis, miliary disease, and it's especially recommended for both children and healthcare workers.

Preventative measures also include education, training, and counseling about TB infection and who is most at risk. Testing and evaluating those most at risk is also vital, as is:

• Coordinating efforts between local and state health departments and high-risk healthcare and congregate settings
• Ensuring the proper cleaning, sterilization, and disinfection of equipment that may be contaminated
• Adequate local or general ventilation of working areas
• Cleaning the air using high-efficiency particulate air (HEPA) filtration or ultraviolet germicidal irradiation
• Using posters and signs to remind people to use proper cough etiquette, like covering the mouth, and respiratory hygiene