Tuberculosis (TB) remains a significant global health challenge, affecting millions worldwide each year. This serious bacterial infection continues to pose a threat, particularly in developing countries. Understanding its nature, how it manifests, and effective control strategies is important for global health efforts.
Understanding Tuberculosis
Tuberculosis (TB) is a disease caused by the bacterium Mycobacterium tuberculosis. These bacteria primarily target the lungs, where they multiply and cause damage. While the lungs are the most common site, Mycobacterium tuberculosis can also spread through the bloodstream to other parts of the body, such as the spine, brain, or kidneys, leading to extrapulmonary TB.
TB bacteria spread through the air. When a person with active TB in their lungs or throat coughs, sneezes, speaks, or sings, they release tiny airborne droplets containing the bacteria. Individuals can become infected by inhaling these droplets, especially in enclosed spaces with poor ventilation. Only people with active TB in their lungs or throat are contagious.
Not everyone exposed to the bacteria develops active disease; many develop latent TB infection (LTBI). In latent TB, the bacteria are present but controlled by the immune system, causing no symptoms and preventing transmission. The infection remains dormant and can become active if the immune system weakens. Active TB disease occurs when bacteria multiply, causing illness and potential spread.
Recognizing the Signs
Recognizing the signs of active tuberculosis, especially pulmonary TB, aids early diagnosis. A persistent cough lasting over two or three weeks is common, sometimes producing blood or mucus. Individuals might also experience chest pain, particularly when breathing or coughing.
Other general symptoms of active TB include fever, night sweats, and unexplained weight loss. Fatigue, weakness, and loss of appetite are frequently reported. These symptoms usually develop gradually and can worsen over several weeks.
While pulmonary TB is the most common form and primary source of transmission, symptoms differ if the infection spreads beyond the lungs. Extrapulmonary TB might cause pain near the infection site, swollen lymph nodes, abdominal pain, or neurological symptoms like confusion or seizures if the brain is affected. The focus remains on pulmonary symptoms due to their direct link to airborne spread.
Detecting and Confirming Tuberculosis
Detecting and confirming tuberculosis involves a series of tests, beginning with initial screening. The tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) are common methods to check for TB infection. A positive result indicates the presence of TB bacteria, but does not differentiate between latent and active disease.
If screening tests are positive, further investigations determine if active TB disease is present. A chest X-ray is often performed to look for characteristic changes or abnormalities in the lungs that suggest active infection. However, a chest X-ray alone is not sufficient for a definitive diagnosis.
To confirm active pulmonary TB, laboratory tests identify Mycobacterium tuberculosis bacteria. Sputum smear microscopy examines mucus coughed up from the lungs under a microscope for bacteria. A sputum culture, growing bacteria from the sample in a lab, is the gold standard for confirmation, though results can take several weeks. For suspected extrapulmonary TB, samples from the affected body part might be collected for similar examination and culture.
Treating Tuberculosis
Treating tuberculosis requires a long course of multiple antibiotic medications to eliminate the bacteria. For drug-susceptible active TB, a typical regimen involves a combination of antibiotics, such as isoniazid, rifampin, pyrazinamide, and ethambutol, taken for six to twelve months. Completing the entire prescribed course is important, even if symptoms improve, to prevent resistance and ensure a complete cure. Stopping treatment prematurely can lead to recurrence and the emergence of drug-resistant strains.
Drug-resistant TB, such as multi-drug resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB), presents a challenge. These forms occur when bacteria become resistant to standard first-line antibiotics, often due to inconsistent or incomplete treatment. Treating drug-resistant TB requires more complex, longer regimens involving different, often more expensive and toxic, medications, extending treatment duration to 18-24 months or longer.
To ensure patients adhere to their medication schedule and complete the full course, Directly Observed Therapy (DOT) is frequently employed. Under DOT, a healthcare worker or trained individual observes the patient taking medication, verifying each dose is consumed. This approach improves treatment success rates and reduces drug resistance.
Preventing Tuberculosis
Preventing tuberculosis involves vaccination and public health measures. The Bacillus Calmette-Guérin (BCG) vaccine is widely used, particularly in countries with a high TB burden. While its effectiveness against adult pulmonary TB can vary, the BCG vaccine protects young children from severe forms of the disease, such as TB meningitis and disseminated TB.
Public health initiatives are important in controlling TB spread. Early diagnosis and prompt treatment of individuals with active TB are fundamental, as this rapidly reduces their infectiousness. Contact tracing, identifying and testing close contacts of someone with active TB, helps find new cases and prevent further transmission. Preventive therapy is also available for individuals with latent TB infection at higher risk of progressing to active disease, averting future illness.
Individuals can also take personal precautions to reduce their risk. Maintaining good personal hygiene, such as covering coughs and sneezes, limits the spread of respiratory droplets. Avoiding prolonged close contact with individuals known to have active TB, especially in poorly ventilated indoor spaces, is advisable. These combined efforts contribute to reducing the overall incidence of TB.