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Tuberculosis (TB) is a chronic infectious disease caused by the bacterium Mycobacterium tuberculosis. It has been a major public health concern for centuries and continues to affect millions of people worldwide. TB primarily targets the lungs, which is referred to as pulmonary tuberculosis, but it can also spread to other parts of the body, including the kidneys, spine, brain, and lymph nodes, in what is known as extrapulmonary tuberculosis.

The disease spreads from person to person through airborne droplets when an infected individual coughs, sneezes, speaks, or even breathes. Despite being highly contagious, not everyone who inhales the bacteria develops active TB. In many cases, the bacteria remain dormant in the body, resulting in a latent TB infection that may become active later if the immune system weakens.

TB is often referred to as a “silent killer” because it can progress slowly, sometimes over months or years, before noticeable symptoms appear. Common early signs may include persistent cough, fatigue, low-grade fever, night sweats, and unintended weight loss. If left untreated, TB can lead to severe health complications, permanent organ damage, and even death.

Globally, tuberculosis remains one of the top infectious disease killers, especially in developing countries where overcrowding, poor nutrition, and limited access to healthcare facilitate its spread. Advances in medical research, antibiotics, and vaccination programs like the Bacillus Calmette-Guérin (BCG) vaccine have helped control TB, but drug-resistant strains and latent infections continue to pose significant challenges.

Causes of Tuberculosis

Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis. This bacterium is slow-growing and has a unique protective cell wall that allows it to survive in the body for long periods, often without causing immediate symptoms. TB primarily affects the lungs, but it can also infect other organs and tissues, leading to extrapulmonary tuberculosis.

The primary cause of TB is the transmission of Mycobacterium tuberculosis from an infected person to a healthy individual. This occurs through airborne droplets expelled when a person with active pulmonary TB coughs, sneezes, speaks, or even breathes. Inhaling even a small number of these bacteria can potentially lead to infection. However, not everyone exposed to the bacteria will develop active TB. The development of the disease depends on the strength of the immune system and other risk factors.

Several factors increase the likelihood of TB infection and progression from latent to active disease. A weakened immune system, caused by conditions such as HIV/AIDS, malnutrition, diabetes, or prolonged use of immunosuppressive medications, makes the body less able to contain the bacteria. Poor living conditions, such as overcrowded homes, inadequate ventilation, and close contact with TB patients, also contribute significantly to the spread of the disease. Lifestyle factors like smoking, excessive alcohol consumption, and substance abuse can further impair immunity, making individuals more susceptible.

Additionally, certain populations, such as children, the elderly, and healthcare workers, are at higher risk due to their vulnerability or frequent exposure to TB bacteria.

Symptoms of Tuberculosis

The symptoms of tuberculosis (TB) can vary depending on whether the infection is latent or active, as well as the part of the body affected. TB most commonly affects the lungs, known as pulmonary tuberculosis, but it can also affect other organs like the kidneys, spine, and brain, which is called extrapulmonary tuberculosis.

In pulmonary TB, the most common form, symptoms develop gradually and may include a persistent cough lasting more than two weeks. This cough can sometimes produce sputum containing blood. Chest pain or discomfort may occur, particularly during breathing or coughing. Patients often experience fatigue, weakness, and a general feeling of illness. Other systemic symptoms include low-grade fever, night sweats, loss of appetite, and unintended weight loss. These symptoms are often subtle at first, which can delay diagnosis.

In extrapulmonary TB, symptoms depend on the organ affected. TB of the kidneys may cause blood in urine and frequent urination. TB of the spine, also known as Pott’s disease, can lead to back pain and spinal deformities. When TB affects the brain or meninges, it may result in headaches, confusion, seizures, or neurological deficits. Lymph node involvement can lead to swollen, painless lymph nodes, often in the neck.

It is important to note that individuals with latent TB infection do not show any symptoms. The bacteria remain dormant in the body, and the person is not contagious. However, latent TB can become active later, especially if the immune system is weakened.

Other general symptoms that can accompany both pulmonary and extrapulmonary TB include night sweats, fever spikes, and a prolonged feeling of malaise. These systemic signs reflect the body’s immune response to the infection.

Types of Tuberculosis

Tuberculosis (TB) can be classified based on the site of infection and the stage of the disease.

1. Pulmonary Tuberculosis:
This is the most common form of TB, affecting the lungs. Pulmonary TB is highly contagious because the bacteria can be expelled into the air through coughing, sneezing, or talking. Symptoms include persistent cough, chest pain, coughing up blood, fatigue, fever, night sweats, and weight loss.

2. Extrapulmonary Tuberculosis:
Extrapulmonary TB occurs when the infection spreads beyond the lungs to other organs or tissues. Common sites include the lymph nodes, kidneys, bones and joints, brain, and meninges. Symptoms depend on the organ affected. For example, TB of the spine (Pott’s disease) causes back pain, while TB of the brain can cause headaches, confusion, or neurological deficits. Extrapulmonary TB is generally less contagious than pulmonary TB.

3. Latent Tuberculosis Infection (LTBI):
In latent TB, the bacteria remain in the body in an inactive state without causing symptoms. People with latent TB are not contagious, but the infection can become active if the immune system weakens.

4. Drug-Resistant Tuberculosis:
This type occurs when the TB bacteria develop resistance to standard anti-TB medications. Multi-drug-resistant TB (MDR-TB) resists at least isoniazid and rifampicin, the two most powerful TB drugs. Extensively drug-resistant TB (XDR-TB) is resistant to multiple first- and second-line drugs, making treatment more difficult and prolonged. Drug-resistant TB usually develops due to incomplete or improper treatment.

Diagnosis of Tuberculosis

The diagnosis of tuberculosis (TB) involves a combination of medical history evaluation, physical examination, laboratory tests, and imaging studies. Accurate and timely diagnosis is essential to confirm infection, determine the type of TB, and begin appropriate treatment.

1. Medical History and Physical Examination:
The first step in diagnosing TB is a thorough assessment of the patient’s symptoms, medical history, and risk factors. Doctors ask about persistent cough, fever, night sweats, weight loss, and exposure to TB-infected individuals. Physical examination may reveal signs such as enlarged lymph nodes, abnormal lung sounds, or other organ-specific indications if TB is extrapulmonary.

2. Tuberculin Skin Test (TST):
Also known as the Mantoux test, this test detects latent TB infection. A small amount of purified protein derivative (PPD) is injected under the skin, and the area is examined 48–72 hours later for swelling or induration. A positive result indicates TB exposure but cannot distinguish between latent and active TB.

3. Interferon-Gamma Release Assays (IGRAs):
These are blood tests used to detect TB infection by measuring the immune system’s response to TB antigens. IGRAs are especially useful in individuals who have received the BCG vaccine, as they are not affected by prior vaccination. Like the skin test, IGRAs cannot differentiate between latent and active TB.

4. Sputum Tests and Culture:
For pulmonary TB, examining sputum is a key diagnostic tool. A sample of mucus from the lungs is tested under a microscope to detect TB bacteria. Sputum culture involves growing the bacteria in a laboratory, which can take several weeks but confirms the diagnosis and allows drug sensitivity testing. Rapid molecular tests like GeneXpert can detect TB bacteria and resistance to rifampicin within hours.

5. Chest X-ray:
Chest radiography helps identify abnormalities in the lungs caused by TB, such as infiltrates, cavities, or nodules. While a chest X-ray can suggest TB, it cannot confirm the diagnosis alone. It is often used in combination with sputum tests and clinical evaluation.

6. Imaging for Extrapulmonary TB:
When TB affects organs other than the lungs, additional imaging techniques such as CT scans, MRI, or ultrasound may be required to detect affected areas and assess the extent of the disease.

7. Biopsy and Histopathology:
In certain cases, particularly extrapulmonary TB, a tissue biopsy may be necessary. The sample is examined under a microscope to detect TB bacteria or characteristic granulomas, which are clusters of immune cells formed in response to infection.

8. Molecular and Drug Sensitivity Tests:
Advanced molecular tests detect the presence of TB bacteria and identify drug-resistant strains. These tests are crucial in cases where first-line treatments fail or in areas with high rates of multidrug-resistant TB (MDR-TB).

Accurate diagnosis of tuberculosis requires a combination of these methods to confirm infection, determine whether it is active or latent, identify drug resistance, and assess the extent of the disease. .

Treatment of Tuberculosis

The treatment of tuberculosis (TB) involves the use of specific antibiotics over an extended period to eliminate the Mycobacterium tuberculosis bacteria from the body. Effective treatment depends on the type of TB, whether it is drug-sensitive or drug-resistant, and the patient’s overall health. Adherence to the full course of medication is essential to ensure complete recovery and prevent the development of drug resistance.

1. Treatment of Latent TB:
Latent tuberculosis infection (LTBI) occurs when TB bacteria are present in the body but remain inactive and asymptomatic. Although individuals with latent TB are not contagious, treatment is important to prevent the infection from becoming active. Common regimens include isoniazid daily for six to nine months or rifampicin for four months. In some cases, a combination of isoniazid and rifapentine is given weekly for three months. Treatment is usually well-tolerated and monitored by healthcare providers to ensure compliance.

2. Treatment of Active Pulmonary TB:
Active TB, particularly pulmonary TB, requires a combination of multiple antibiotics, known as first-line anti-TB drugs. The standard treatment typically lasts six months and is divided into two phases:

Intensive Phase (first 2 months): This phase usually involves four drugs—isoniazid, rifampicin, pyrazinamide, and ethambutol. The purpose of this phase is to rapidly reduce the bacterial load and prevent the development of drug resistance.

Continuation Phase (next 4 months): This phase typically uses isoniazid and rifampicin to eliminate any remaining bacteria and prevent relapse.

Patients must take the medications exactly as prescribed. Missing doses or stopping treatment early can lead to drug resistance, treatment failure, and continued transmission of TB.

3. Treatment of Extrapulmonary TB:
When TB affects organs other than the lungs, such as the kidneys, bones, or brain, treatment may be similar to pulmonary TB but sometimes extended beyond six months depending on the site and severity. For example, TB meningitis or spinal TB may require treatment for 9–12 months. In some cases, surgical intervention may be necessary to remove infected tissue or relieve complications.

4. Drug-Resistant TB Treatment:
Drug-resistant TB, including multi-drug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB), requires specialized treatment regimens. MDR-TB resists at least isoniazid and rifampicin, while XDR-TB resists multiple first- and second-line drugs. Treatment involves second-line drugs, which are often less effective, more toxic, and require a longer duration of therapy, sometimes up to 18–24 months. Patients are closely monitored for side effects and treatment response.

5. Supportive Care During Treatment:
In addition to antibiotics, supportive care is important for TB patients. Adequate nutrition, rest, and management of coexisting conditions like diabetes or HIV improve treatment outcomes. Regular follow-up visits are necessary to monitor response to treatment and detect any side effects early.

6. Directly Observed Therapy (DOT):
To ensure adherence, many healthcare programs use directly observed therapy, where a trained healthcare worker supervises the patient taking each dose of medication. DOT helps prevent treatment interruption, reduces drug resistance, and improves recovery rates.

Successful treatment of tuberculosis not only cures the individual but also reduces transmission in the community.