Tuberculosis disease

Tuberculosis (TB): A Complete Guide to Causes, Symptoms, Diagnosis, and Treatment

Introduction

Tuberculosis, often abbreviated as TB, is a chronic infectious disease caused by the bacterium Mycobacterium tuberculosis. It most commonly affects the lungs but can also involve other organs such as the brain, spine, kidneys, and lymph nodes. Despite being both preventable and curable, TB continues to be one of the top ten causes of death worldwide, particularly in developing countries. It spreads from person to person through the air when an infected individual coughs, sneezes, speaks, or spits. Although significant progress has been made in TB control through public health efforts and antibiotics, the disease remains a major global health concern due to the emergence of multidrug-resistant strains and its strong association with HIV/AIDS.

Understanding Tuberculosis

Tuberculosis can present in two main forms: latent TB infection and active TB disease. In latent TB, the bacteria remain in the body in an inactive state and cause no symptoms. Individuals with latent TB are not contagious but are at risk of developing active TB if their immune system becomes weakened. Active TB, on the other hand, occurs when the immune system fails to contain the bacteria, leading to illness that often requires immediate medical treatment. Most cases of active TB are pulmonary, meaning they involve the lungs, but extrapulmonary tuberculosis can affect other areas like the pleura, lymph nodes, bones, or the central nervous system.

Causes and Risk Factors

The causative agent of tuberculosis, Mycobacterium tuberculosis, is a slow-growing, rod-shaped bacterium with a waxy outer coating that makes it resistant to environmental changes and many antibiotics. The bacteria primarily spread through airborne particles released when someone with active TB coughs or sneezes. People nearby may inhale the bacteria into their lungs, where the infection can begin. Certain factors increase the risk of developing TB, including HIV infection, diabetes mellitus, malnutrition, chronic kidney disease, smoking, excessive alcohol use, and prolonged exposure to an infected person, particularly in crowded or poorly ventilated environments such as prisons or refugee camps. Health workers and individuals with compromised immune systems are also at increased risk.

Signs and Symptoms

The symptoms of tuberculosis can vary depending on whether the disease is active or latent, and which part of the body is affected. In pulmonary TB, the most common symptoms include a persistent cough lasting more than three weeks, chest pain, and coughing up blood or sputum. These respiratory symptoms are often accompanied by systemic signs such as fever, night sweats, fatigue, unexplained weight loss, and loss of appetite. Extrapulmonary TB may present with localized symptoms based on the organ involved. For instance, TB of the lymph nodes may cause painless swelling, spinal TB (Pott’s disease) can result in back pain and deformity, while TB meningitis may lead to headache, vomiting, and neurological symptoms. If left untreated, active TB can be fatal and may cause irreversible organ damage.

Diagnostic Approaches

Diagnosing tuberculosis accurately is essential for effective treatment and preventing transmission. The first step often involves a clinical evaluation and a detailed history of symptoms, travel, or exposure. Several diagnostic tools are used depending on the suspected type and location of TB. The tuberculin skin test (Mantoux test) is commonly used to detect latent TB, where a purified protein derivative (PPD) is injected under the skin, and the response is measured after 48 to 72 hours. A positive result suggests TB exposure but cannot differentiate between latent and active TB.

More advanced tests include Interferon-Gamma Release Assays (IGRAs), which are blood tests that measure immune response to TB antigens. These tests are more specific and are not affected by prior BCG vaccination. For pulmonary TB, sputum smear microscopy and culture tests remain the gold standard for detecting acid-fast bacilli. Additionally, molecular tests such as the GeneXpert MTB/RIF assay provide rapid detection of Mycobacterium tuberculosis and resistance to rifampicin, a key TB drug. Imaging techniques like chest X-rays or CT scans help identify lung lesions, cavities, or pleural effusions, while biopsies or fluid analysis may be necessary for diagnosing extrapulmonary forms of the disease.

Treatment and Management

Tuberculosis is curable with the correct use of antibiotics over a specified period. The World Health Organization (WHO) recommends a standard treatment regimen known as DOTS (Directly Observed Treatment, Short-Course) for drug-sensitive TB. This includes an intensive phase of four first-line antibiotics—isoniazid, rifampicin, pyrazinamide, and ethambutol—for the first two months, followed by a continuation phase of isoniazid and rifampicin for another four months, making a total of six months of therapy. Adherence to the full course of treatment is crucial, as incomplete treatment can lead to relapse and drug resistance.

For patients with multidrug-resistant TB (MDR-TB), which is resistant to at least isoniazid and rifampicin, second-line drugs like fluoroquinolones, linezolid, bedaquiline, and delamanid are used, often over 9 to 24 months. These treatments are more toxic, expensive, and less effective than standard therapy. Individuals co-infected with HIV require special consideration and may be treated simultaneously for both conditions, although careful monitoring for drug interactions and side effects is necessary. In all cases, regular follow-ups, liver function tests, and adherence support are essential for successful outcomes.

Complications of Untreated TB

Without treatment, TB can result in severe complications and even death. Chronic pulmonary TB can lead to lung destruction, bronchiectasis, and respiratory failure. Extrapulmonary TB may cause permanent damage to affected organs, such as spinal deformity in vertebral TB or neurological deficits in TB meningitis. Other complications include the formation of lung cavities, pleural thickening, and the spread of infection throughout the body in a condition called miliary TB, which is life-threatening. Additionally, patients undergoing long-term TB treatment may experience drug-related complications such as liver toxicity, peripheral neuropathy, and vision changes.

Prevention Strategies

Preventing TB involves a combination of public health measures, vaccination, early diagnosis, and treatment adherence. The BCG vaccine, derived from Mycobacterium bovis, is widely administered to newborns in countries with a high burden of TB. While it does not prevent infection, it offers protection against severe forms like TB meningitis in children. Preventing TB transmission also requires prompt identification and treatment of active TB cases. In healthcare and high-risk settings, respiratory precautions, including wearing N95 masks, ensuring adequate ventilation, and conducting contact tracing, are essential to limit spread. People with latent TB who are at high risk of progression to active disease may be given preventive therapy, such as isoniazid for 6 to 9 months.

Tuberculosis and HIV: A Dangerous Duo

TB and HIV form a deadly syndemic. HIV weakens the immune system, making it more likely for latent TB to become active. TB, in turn, accelerates the progression of HIV disease. Co-infected individuals are more difficult to diagnose and treat, and they are at higher risk for death. The World Health Organization recommends integrated care, where patients are screened for both diseases and treated with a coordinated approach. This includes antiretroviral therapy (ART) for HIV and TB treatment started promptly, often within two weeks of beginning ART to reduce mortality.

Global Burden and Public Health Impact

Tuberculosis continues to exert a heavy toll on global health. According to the WHO’s Global TB Report 2024, an estimated 10.6 million people fell ill with TB in 2023, and about 1.3 million deaths were recorded among HIV-negative individuals, with an additional 167,000 deaths among HIV-positive individuals. The burden is highest in South Asia, Sub-Saharan Africa, and parts of Eastern Europe. Poverty, limited healthcare access, undernutrition, and stigma contribute significantly to TB’s spread. Efforts such as the End TB Strategy aim to reduce TB deaths by 90% and cases by 80% by 2035, emphasizing universal health coverage, research, and better diagnostics and treatments.

Conclusion

Tuberculosis is more than just a lung infection—it is a complex, chronic, and often socially stigmatized disease that continues to challenge healthcare systems around the world. While modern medicine has made TB curable and preventable, millions still suffer from the disease due to poor access to care, late diagnosis, and the rise of drug-resistant strains. Effective control of TB requires a multi-pronged approach involving early detection, strict treatment adherence, vaccination, public education, and robust public health infrastructure. With coordinated global efforts, ending the TB epidemic is a reachable goal in the coming decades.

References

1. World Health Organization (WHO). Global Tuberculosis Report 2024.

2. Centers for Disease Control and Prevention (CDC). Tuberculosis (TB) Facts.

3. Kumar & Clark’s Clinical Medicine, 10th Edition.

4. Harrison’s Principles of Internal Medicine, 21st Edition.

5. National Tuberculosis Control Program (Pakistan) – www.ntp.gov.pk