Tuberculosis, also known as TB, is a contagious bacterial infection that can be found nearly anywhere in the body, but is found most commonly in the lungs. This because the bacteria that is responsible for TB, Mycobacterium Tuberculosis, is transmitted through the air as it does not thrive on surfaces . Although TB has been discovered over 100 years ago, it is still one of diseases that cause the most deaths annually . To get more insight why TB still exists at large scale to this, we must look at how TB works, where it is active and how it can be treated at the moment.
Material and Methods
The initial studies selected for this review were identified with extensive manual data search. For each literature stated multiple studies with roughly the same results have been found. General information regarding TB has been acquired with basic data search on various search engines and biotechnology libraries such as NCBI. The answer of why TB is still one of the leading causes of deaths by diseases worldwide can be found in different aspects of the disease. At first, we will be focusing on general information of Tuberculosis, the bacteria Mycobacterium Tuberculosis and its functions. Later we will also look at the areas where TB is most active, treatment, diagnosis, symptoms and similar topics.
Tuberculosis spreads via the air, which means that the lungs are usually the first places to be infected with the bacteria. The Mycobacterium Tuberculosis is absorbed by white blood cells, but will not be broken down by them. The bacteria will stay dormant in this stage (Pulmonary TB), occasionally for a long time . Eventually, the bacteria will invade a white blood cell and multiply until the white blood cell dies and breaks open. More TB bacteria will spread from there and invest other cells, forming a granuloma . By doing so they often travel to other body-parts . This technique of sitting inside the white blood cells makes it harder to get them contacted with treatment. Moreover, since Mycobacterium Tuberculosis is known for growing slowly  it may often be unnoticed before it goes on to the next stage, Secondary TB (active TB).
This happens when the TB bacteria break out of the white blood cells granuloma . Reasons for this happening can vary. Factors like stress, growing older, having diabetes, HIV or a weakened immune system. If this stage is not treated quickly enough there is a risk of TB bacteria spreading to other body parts, making it increasingly difficult to treat it well . It also increases the chance of developing Multi Drug Resistant TB(MDR-TB) . This variant of TB has shown to be resistant to the currently used treatment methods. People infected with MDR-TB have fewer options for treatment, being forced to expensive treatment methods which can take over 2 years compared to 6 to 12 months for dormant or active Tuberculosis . If TB is not treated in time, possible effects may include organ failure, paralysis and eventually death.
Mycobacterium Tuberculosis is a bacterium that does not thrive well on surfaces, which is why it transmits through the air instead. Infected people‘s coughs, sneezes, talking, singing or anything similar will emit droplets of moisture which can contain the bacteria. When other people breathe in this moisture they have a chance of getting infected as well . Not all stages of TB can be transmitted though. Dormant TB, where the bacteria is still inside the white blood cells has no way of being transmitted to other people . All stages afterwards are contagious and infected people are often isolated to stop the spreading of TB. Despite this, Mycobacterium Tuberculosis is a slow growing bacterium, and does not transfer easily from one person to another. In fact, people that stay close to an infected person for 6 months have a roughly 50% chance of acquiring the disease as well . The reason why people are still being isolated is because it is hard to track who is infected and who is not, due to early dormant stages of TB. Additional reasons include it being a lethal disease and there is no quick way to treat TB to this date. Most people that are being isolated are either infected with MDR-TB, or are risk factors. Risk factors are people more susceptible for TB and include children, HIV-positive people, diabetes patients, smokers or other conditions which reduce the working of the immune system (most notably in the lungs .
Dormant Tuberculosis has no symptoms, and goes often unnoticed until it passes on to the next stage, where it becomes active. Active Tuberculosis however, is where granuloma start to break . Symptoms of this may include continuous coughs, Hemoptysis, consistent (low grade) fevers, night sweats, chests pains, loss of appetite and unexplained weight loss . Most of these symptoms are due to damage of the lungs and the spreading of TB to other body parts may have additional symptoms as well, including feeling tired all the time, a stiff feeling in joints most of the time and eventual function loss of infected body parts . If TB is not cured, then the eventual result will be death.
The amount of newly infected people and number of casualties annually has slowly decreased over the past decade; however, TB still remains at large. Researches show over 80% of the casualties of TB are found in lower- to middle-income countries, whereas the mortality rates in high-income countries are always under 1 per 100000 capita. Most notably is the difference in middle-income countries, ranging from low incidents rate such as 2.0 per 100000 capita up to 40.0 per 100000 capita. Specific countries where TB has a high incidents rate are Nigeria (99 per 100000 capita), Korea (61 per 100000 capita), Indonesia (40 per 100000 capita), Afghanistan (37 per 100000 capita) and India (36 per 100000 capita). Multiple countries around southern Africa got similar rates as well . In the past few years there has been a small increase in TB incidents in western countries, most notable in Europe. Over 70% of these incidents include immigrants .
Not all Diagnose methods for TB can be used at all stages. The following methods are used to diagnose TB.
A blood sample tested on TB bacteria to see how the immune system reacts.
Dormant TB, Active TB, MDR-TB
A TB protein will be injected into the skin. After 3 days result show a red spot (TB negative) or a swollen spot (May be TB)
Dormant TB, Active TB, MDR-TB
A CT scan to check for the lungs for signs of infections.
Active TB, MDR-TB
A scope is inserted inside the nostrils or mouth to see inside the lungs and airways.
Active TB, MDR-TB
A lab examing a sample of the mucus.
Active TB, MDR-TB
A small sample of lung tissue is taken to analyze.
Active TB, MDR-TB
Table 1: Diagnose methods to determine if a person has Tuberculosis or not, focusing on their lungs .
Imaging tests and bronchoscopy cannot diagnose dormant TB. This is due to the fact that dormant TB is not showing any symptoms visible by the eye . White blood cells will be infected, but not directly observable. Blood tests, skin tests and imaging tests are used most commonly, yet CT scans of a TB infected person look very alike to some other diseases as well, often being misdiagnosed as lung cancer or pneumonia. Indicators on a CT scan for these diseases and TB are nodules (cell clusters) within the lungs. The symptoms for these diseases are similar as well: fever, continuous coughs, hemoptysis, weight loss, loss of appetite and expectoration. There are differences between these diseases in the way they work such as average age of infected people for both diseases, bacterial infection for tuberculosis and pneumonia against mutations for lung cancer, and similar. Yet these differences are not easy to observe on a single person, while a prediction can be made on the conditions of the person it has shown that this is not a reliable method of indicating the correct disease  .
Due to tuberculosis often being diagnosed as another disease has slowed down treatment on multiple incidents. Another cause of this is the fact that treatment for tuberculosis, pneumonia and lung cancer are very different and do not work on each other  . Treatment medicine for TB include
- ethambutol, or Myambutol, discontinued
- rifampin, or Rifadin and Rimactane, some brands discontinued
At least two of these medicines will be used simultaneously at once to make sure that TB will not get resistant to the medicine too quickly . TB will eventually get resistant to this medicine, which usually happens in a few weeks. In that case the treatment will switch to two other medicines . An example of treatment would be short-course chemotherapy, which is the use of isoniazid (INH), rifampin, and pyrazinamide in combination for at least six months . Medicine needs to be used for six to twelve months continuously. Failure in doing so may result in recurring TB or MDR-TB, which is much harder to cure. A doctor might recommend DOT (directly observed therapy), where a health-care professional will meet an infected person to make sure that the prescribed medicine is used correctly . If the medicine is not used frequently enough or not in the correct way, Dormant TB or active TB can change into MDR-TB . People who are not on DOT or isolation can use their medicine at home, and do not have to go a hospital every time nor having to stay there.
Another option to treat TB is thoracentesis, a procedure that removes fluid from the scape between the outside of the lungs and the wall of the chest . This surgery will not treat TB completely, but will decrease the effects of Tb by considerable amounts. This method will not decrease the time needed for treatment by medicine used in combination with thoracentesis, but rather focuses on reducing the making it more bearable for the infected person and is used most often for people who have been isolated to stop spreading of TB. Other common objectives for people isolated by pneumonia or TB include :
- To decrease discomfort
- To facilitate the exchange of oxygen and carbon dioxide in the lungs
- To prevent atrophy from the increased bed rest
- To prevent social withdrawal
Tuberculosis proves to be a disease that is quite hard to get, yet hard to cure as well. The bacterium does not thrive on surfaces and respectively medicine does not work very well on it. Studies show that being close to someone with active TB over a period of six months gives a chance of roughly 50% of getting infected with dormant TB . Yet the time needed to get cured of TB is about six to twelve months respectively. Additional proof on this fact are the demographics. Nearly all outbursts of TB over the past fifteen years have all been in low- to middle-income countries which shows that factors impact TB negatively there compared to middle- to high-income countries .
In most middle- to high-income countries where the average person can afford the medicine they will be aware of being infected with a contagious disease thus reducing the chances of spreading TB. Additionally, medicine will be harder to acquire in most low- to middle-income countries, and lower quality of health-care, diagnosis and regulation will make spreading of TB more likely. Diagnosis in these countries may be less accurate and often misdiagnose TB as lung cancer or pneumonia thus incorrect treatment will be used. Meanwhile someone could be infecting others with TB without knowing it. Another possibly contributing factor may be the amount or risk factor per capita in the countries where TB is active. Most notable are the people with HIV, smokers, drug users and other diseases affecting the immune system. Additional influencing factors might be regulation of people where more people near each other can increase the risk of spreading TB.
Future research needs to be executed to conclude if this is correlation, causation or coincidence. A lot of research is focusing on TB presently trying to cure the world of this disease. Progress at the moment is progressing slow but steady and if the steady pace is maintained then Tuberculosis might have disappeared from the list of leading diseases of most deaths annually within a few decades.