Tuberculosis (TB) is transmitted between humans through tiny droplets in the air. When an individual with TB of the lungs or throat coughs, sneezes, or even speaks or sings, TB bacteria become airborne. People infected with these bacteria do not always become sick, and thus some individuals have a latent TB infection. However, people become sick in cases where their immune system is weakened due to some other causes.
Causes of Infection
Mycobacterium tuberculosis bacterium
＜Microscopic view of mycobacterium tuberculosis＞ CDC
TB is transmitted via tiny droplets that travel through the air. People breathe in the TB bacteria contained in these droplets and become infected, usually when a person with TB of the lungs or throat coughs, sneezes, speaks, or even sings. Not all people infected with TB bacteria become sick.
There are two main TB-related conditions and these are referred to as TB disease and latent TB infection (LTBI). In most cases, people are asymptomatic, meaning they have latent TB infection. TB disease develops when the immunity system of a person becomes weak.The risk of contracting TB disease becomes extremely high when an individual is concomitantly infected with HIV/AIDS.
The symptoms of TB disease tend to manifest depending on where the TB bacteria attack the body of the patient.TB bacteria usually attack the lungs but can also attack any other part of the body, including the kidneys, spine, or brain.
TB disease in the lungs has symptoms that may include a bad cough that lasts three weeks or more, chest pain, and coughing up blood or sputum (phlegm from deep inside the lungs). Other symptoms observed can include weakness or fatigue, weight loss, loss of appetite, chills, fever, and night sweats.
Diagnosis and Treatment
Two types of tests are used to diagnose TB bacteria infections: tuberculin skin tests and TB blood antibody tests. A positive TB skin or blood test indicates only that someone has been infected with the TB bacteria. Other testing, including chest X-rays and sputum examination, is required to see if someone definitely has TB disease.
TB disease can be treated by taking several drugs at the same time, usually for six to nine months. It is critical to finish the entire course of drugs exactly as prescribed. If someone stops taking the drugs too soon, they may relapse. Moreover, when the drugs are not taken correctly by the patient, the TB bacteria may become drug resistant.
Of all approved drugs, the first-line anti-TB agents that are at the core of treatment regimens currently include isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA). Modifications should be made under certain special circumstances for people with HIV/AIDS infection, drug resistance, and/or pregnancy, or for the treatment of children.
Many countries also use a vaccine called BCG, although it does not completely prevent TB. BCG may also cause tuberculin skin tests to show a false positive result, meaning extra care is required with diagnosis.
Regions at High Risk of Infection
Over 95% of cases of TB disease and deaths from TB occur in developing countries. The largest number of new TB cases occurred in the Asia, accounting for 61% of new cases globally, followed by Africa with 26% of new cases in 2015. Overall, however, the number of cases of TB disease has been gradually falling.
Estimated Number of Infected People
It is estimated that 10.4 million people contracted TB in 2015. Also in 2015, about 1.2 million people infected with HIV/AIDS became newly infected with TB, with an estimated 71% of that number being patient cases in Africa.
Estimated Number of Deaths
About 1.8 million people died from TB in 2015. Of those 1.8 million, about 170,000 were children under 14-years-old. On the other hand, it is estimated that 49 million lives were saved through diagnosis and treatment for TB during 2000 to 2015.
Initiatives by Pharmaceutical Companies and NGOs
The World Health Organization (WHO) End TB Strategy, adopted by the World Health Assembly in May 2014, outlines global impact targets to reduce TB deaths by 90% and to cut new cases by 80% between 2015 and 2030.