Tuberculosis is a complex disease. On the one hand, it can affect different areas of the human body, such as the lungs, the lymph nodes, the skeletal system or the brain. On the other hand, different types of TB exist, which can either be completely curable, but in the case of drug-resistant forms could also mean certain death.
According to the WHO, 10% of latently infected people on average develop active TB, which means that the bacteria form isolated, nodular inflammation points, which the immune system can no longer control. As a weakened immune system is the prerequisite, an active infection often occurs in people, who suffer from serious, chronic illnesses such as HIV infection, drug addicts, or even in children.
In about 80% of patients the TB bacteria affect the lungs. For these patients, there are two types of tuberculosis: the “open” or pulmonary-positive and “closed” or pulmonary-negative tuberculosis. In the case of open tuberculosis an inflammation developed inside the lungs that the immune system is not able to isolate, i.e., bring under control. This enables TB bacteria to be released through the respiratory tract (e.g., through coughing) and means that this type of tuberculosis infection is contagious. In fact, only a few droplets are already enough to spread the infection – for example, by being in the immediate vicinity of an infected person who had just coughed, sneezed or spat (even if only while speaking). In the case of closed tuberculosis, the opposite is the case, and there is no risk of infection as the inflammation is on the lungs’ periphery and not inside.
For the remaining 20% of cases other organs are affected by the bacteria – most commonly the lymph nodes, but also the bones and joints, spine, intestines, kidneys or brain – in what is described as extra-pulmonary (“EP”) tuberculosis. As with the closed tuberculosis, EP tuberculosis is not contagious.
Recently, drug-resistant forms of TB have also evolved through misuse or inappropriate use as well as poor quality of antibiotics. These drug-resistant forms range from multi-drug resistant TB (MDR-TB), which can only be treated with expensive, newer antibiotics over a longer period, up to extensively drug-resistant TB (XDR-TB), which is resistant to almost all forms of medical treatment with little hope of survival for the victims.
It is important not to forget that drug resistance is also difficult and costly to diagnose due to the involving and/or expensive laboratory tests required, and that one can be infected directly with the most resistant form of TB, without having to “undergo” the treatable forms.
In the next section, you can read further about the symptoms of tuberculosis and methods by which tuberculosis is diagnosed.