Overview

Tuberculosis is a contagious bacterial infection primarily affecting the lungs. Caused by the bacterium Mycobacterium tuberculosis, TB spreads through the air when an infected person coughs, sneezes, or speaks.

Types of Tuberculosis

TB can be classified based on its location in the body and its stage of development:

• Pulmonary tuberculosis: This is the most common form, affecting the lungs. Symptoms include persistent cough, chest pain, weight loss, fatigue, and sometimes coughing up blood.
  • Primary tuberculosis: The initial infection.
  • Post-primary or reactivation tuberculosis: A recurrence of a previously inactive infection.
• Extrapulmonary tuberculosis: This form affects organs outside the lungs, such as lymph nodes, bones, joints, the brain, and kidneys. Symptoms vary depending on the affected area.

Latent vs. Active Tuberculosis

• Latent tuberculosis infection (LTBI): The bacteria are present in the body but inactive. People with LTBI do not feel sick and cannot spread the disease. However, the infection can become active.
• Active tuberculosis disease: The bacteria are active and multiplying, causing symptoms. People with active TB can spread the disease to others.

Early diagnosis and treatment are crucial for preventing the spread of TB and improving patient outcomes.

Prevalence

Tuberculosis (TB) prevalence varies significantly worldwide. While the United States has made substantial progress in controlling the disease, it remains a public health concern in certain populations.

Compared to many other countries, the TB incidence in the U.S. has been steadily declining for decades. According to the Centers for Disease Control and Prevention (CDC), the TB rate in 2020 was 2.5 cases per 100,000 people, marking a continued decrease from previous years.

However, it's essential to recognize that TB is not eradicated in the U.S. Specific populations, including people experiencing homelessness and those with compromised immune systems, remain at increased risk. Ongoing surveillance, prevention, and treatment efforts are crucial to maintaining low TB rates and addressing disparities in affected communities.

Symptoms

Tuberculosis (TB) symptoms can vary widely depending on whether the infection is active or latent, and whether it affects the lungs (pulmonary TB) or other parts of the body (extrapulmonary TB).

Latent TB typically causes no symptoms. The individual is infected but does not feel sick and cannot spread the disease.

Active TB symptoms can be more noticeable.

• Persistent cough lasting 3 weeks or longer
• Coughing up blood or mucus
• Chest pain or discomfort
• Fatigue and weakness
• Unintentional weight loss
• Loss of appetite
• Fever, often worse in the evening
• Night sweats

Extrapulmonary TB: Symptoms vary based on the affected organ. Common areas include:

• Lymph nodes: Swelling or lumps
• Bones and joints: Pain, swelling
• Brain (meningitis): Headache, stiff neck, neurological symptoms
• Kidneys: Blood in urine, painful urination

Not everyone infected with TB will develop active disease. Some individuals with latent TB may never progress to active TB.

Transmission

Tuberculosis (TB) is primarily spread through the air when a person with active TB disease coughs, sneezes, or speaks. Tiny droplets containing TB bacteria are released into the air and inhaled by others nearby. Close and prolonged contact with an infected individual increases the risk of transmission.

It's important to note that people with latent TB infection cannot spread the disease as they do not have active TB bacteria in their lungs.

Causes

Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. The infection is primarily spread through the air when someone with active pulmonary tuberculosis coughs, sneezes, or speaks, releasing respiratory droplets containing the bacteria.

However, not everyone exposed to the bacteria develops active tuberculosis; the immune system can often control the infection, leading to latent tuberculosis, where the bacteria remain inactive in the body without causing symptoms.

Risk Factors

Several factors can increase your risk of contracting or developing active tuberculosis (TB):

• Close contact with an infected individual: Spending significant time with someone who has active TB can increase your exposure to the bacteria.
• Weakened immune system: Conditions that compromise the immune system make you more susceptible to TB infection and disease progression. These include:
  • HIV/AIDS
  • Malnutrition
  • Immunodeficiency disorders
  • Diabetes
  • Chronic kidney disease
  • Certain types of cancer and their treatments
• Age: Infants and older adults are at higher risk due to less developed or weakened immune systems.
• Living in or traveling to areas with high TB prevalence: Certain regions have higher rates of TB, increasing your exposure risk.
• Occupational exposure: Healthcare workers, prison staff, and those working in homeless shelters are at increased risk due to potential exposure to the bacteria.
• Substance abuse: Alcohol and drug use can weaken the immune system and increase TB risk.
• Homelessness: Lack of adequate housing and access to healthcare can contribute to TB vulnerability.

It's important to note that having one or more of these risk factors does not guarantee that you will develop TB. However, being aware of them can help you take steps to protect yourself.

Diagnosis

Diagnosing tuberculosis (TB) involves a combination of medical history, physical examination, and laboratory tests.

• Medical history and physical examination: A healthcare provider will inquire about symptoms, travel history, and potential exposure to TB. A physical exam may reveal signs of TB, such as fever, weight loss, or abnormal lung sounds.
• Tuberculin skin test (TST) or interferon-gamma release assay (IGRA): These tests help determine if you have been infected with TB bacteria.
  • TST: A small amount of tuberculin is injected under the skin, and the area is checked for a raised, hard bump 48-72 hours later.
  • IGRA: A blood test that detects immune system responses to TB bacteria.
• Chest X-ray or CT scan: These imaging studies can help identify abnormalities in the lungs associated with TB.
• Sputum culture: A sample of mucus coughed up from the lungs is examined for the presence of TB bacteria.
• Other tests: Depending on the suspected location of TB, additional tests may be performed, such as urine tests, blood cultures, or cerebrospinal fluid analysis.

Early and accurate diagnosis is crucial for effective treatment and preventing the spread of TB. If you suspect you may have TB, it's essential to seek medical attention promptly.

Treatment

The primary treatment for tuberculosis (TB) involves a combination of antibiotics taken over an extended period. The standard regimen typically includes:

• Isoniazid (INH)
• Rifampin
• Pyrazinamide
• Ethambutol

Treatment Duration and Regimen

The typical course of treatment lasts between 6 to 9 months, depending on factors such as the type of TB (e.g., pulmonary or extrapulmonary), drug susceptibility, and the patient's overall health.

Isoniazid (INH) is usually taken daily for the entire duration, often alongside other drugs, particularly in the initial phase of treatment.

Importance of Completing the Full Course

Completing the full course of treatment is crucial for curing the infection and preventing the development of drug-resistant TB strains. Missing doses or stopping treatment early can lead to treatment failure and the emergence of drug resistance, making the disease much harder to treat.

Directly Observed Therapy (DOT)

To ensure adherence and maximize the effectiveness of treatment, TB therapy is often administered under medical supervision through a method known as Directly Observed Therapy (DOT).

In DOT, a healthcare provider or trained individual directly observes the patient taking their medication. This approach is particularly important in managing TB to prevent the development of drug-resistant strains and to ensure successful treatment outcomes.

Drug-Resistant Tuberculosis

For cases involving drug-resistant TB, treatment may require the use of second-line drugs, which are often more toxic and need to be taken for longer periods, sometimes up to 18-24 months.

Drug-resistant TB requires specialized care and may involve a combination of additional drugs, including newer agents like bedaquiline and delamanid.

Monitoring and Follow-Up

Regular follow-up and monitoring are essential during TB treatment to assess the patient's response to therapy, manage any side effects, and ensure the bacteria are fully eradicated. Patients are often required to undergo periodic sputum tests, chest X-rays, and other evaluations to confirm that the infection is resolving.

Prevention

Preventing tuberculosis (TB) involves a combination of strategies aimed at reducing transmission and protecting vulnerable populations.

• Vaccination: The Bacillus Calmette-Guérin (BCG) vaccine is used in many countries to protect infants and young children from severe forms of TB, such as meningitis. While its effectiveness in preventing adult pulmonary TB is debated, it remains a valuable tool in TB control programs in high-burden countries.
• Screening and treatment of latent TB infection: Identifying individuals with latent TB infection and providing preventive treatment can help prevent the progression to active disease.
• Infection control: Implementing strict infection control measures in healthcare settings and other high-risk environments is crucial to preventing the spread of TB. This includes isolating patients with active TB, using respiratory protection, and ensuring proper ventilation.
• Early diagnosis and treatment: Promptly diagnosing and treating active TB cases is essential to prevent further transmission.