Tuberculosis

Article

July 6, 2022

Tuberculosis is an infectious disease usually caused by the bacterium Mycobacterium tuberculosis (MTB). Tuberculosis usually affects the lungs, although it can affect other parts of the body as well. Most infections do not show symptoms, in which cases are called latent tuberculosis. About 10% of latent infections progress to active tuberculosis. If untreated, active tuberculosis kills half of infected people. The classic symptoms of active tuberculosis are chronic coughing with blood, sputum, fever, night sweats and weight loss. Infection of other organs can cause a number of other symptoms. Tuberculosis is spread through the air when people with active tuberculosis in the lungs cough, spit, talk, or sneeze. People with latent tuberculosis do not transmit the disease. Active infection is more common among smokers and people with HIV/AIDS. The diagnosis of active tuberculosis is supported by chest x-rays, microscopic examinations, and cultures of body fluids. The diagnosis of latent tuberculosis is based on a tuberculin test or blood tests. Prevention measures include screening for risk groups, early detection and treatment of cases and vaccination with the bacillus Calmette-Guérin (BCG vaccine). Risk groups include people who share a home or workplace with people with active tuberculosis. Treatment consists of administering several antibiotics over a long period of time. Antibiotic resistance is a growing problem, and the number of cases of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) is increasing. It is estimated that about one third of the world's population is infected with latent tuberculosis. . Every year new cases of infection occur in about 1% of the population. In 2016, there were more than 10 million cases of active tuberculosis worldwide, causing about 1.3 million deaths. This makes tuberculosis the leading cause of death from infectious diseases. More than 95% of these deaths occurred in developing countries, mainly in India, China, Indonesia, Pakistan and the Philippines. Since the year 2000, the number of new cases each year has been decreasing. In many African and Asian countries about 80% of the population has a positive tuberculin test, while in the United States this figure is only 5–10% of the population. The disease has been present in humans since ancient times.

Signs and symptoms

Among its symptoms, we can mention cough with secretion, fever (most commonly at dusk), night sweats, lack of appetite, weight loss, easy tiredness and muscle pain. Difficulty in breathing, elimination of blood (hemoptysis) and accumulation of secretion in the pulmonary pleura are characteristic in more severe cases.

Transmission

Tuberculosis is transmitted by the bacilli expelled by an infected individual when coughing, talking, sneezing or spitting. Tuberculosis is spread through airborne aerosols that are expelled when people with infectious tuberculosis cough or sneeze. Close contacts (people who have frequent contact) are at high risk of becoming infected. Transmission occurs only from people with active infectious tuberculosis (not from those who have the latent disease). The probability of transmission depends on the degree of infection of the person with tuberculosis and the amount expelled, the form and duration of exposure to the bacillus, and the virulence. The chain of transmission can be interrupted by isolating patients with active disease and initiating effective antituberculosis therapy. Resistant tuberculosis is transmitted in the same way as drug-sensitive forms. Primary resistance develops in people initially infected with resistant microorganisms. The secondary resistance