Overview: What is tuberculosis?
There are several names for this disease, but they are outdated: consumption, white plague, white death, the moths. Tuberculosis (or TB for short) is caused by bacteria (mycobacterium tuberculosis). Humans are the only reservoir for the disease. You are particularly at risk of infection if you are in a room where a person who is already ill is or has recently been. If the affected person has exhaled fine droplets while coughing or talking, there is a risk that you will inhale this infectious aerosol and become infected. Not every infection leads to illness: around 90 percent of all infected people are „latently“ infected, i.e. the person carries the bacterium but does not fall ill. 10% of infected people develop an active disease, mostly pulmonary tuberculosis . In principle, however, any organ can be affected by active tuberculosis. Most cases of active disease occur within the first two years after infection. The typical signs are Cough, sputum, fever, weight loss.
However, the transmission of tuberculosis by other means is much rarer than such a droplet infection. For example, the bacteria can be found in foods such as meat or milk. TB bacteria can also be transmitted via inadequately disinfected syringes, needles or other medical instruments.
If treatment is successful, tuberculosis is often cured without leaving any lasting consequences.
Tuberculosis – frequency and age
There are around ten million new cases of tuberculosis worldwide every year, and around 1.5 million people die from the disease. The countries most affected are in the southern half of Africa and in Asia.
In Switzerland, between 463 and 611 new cases have been reported each year since 2010 (Germany: 4317 to 5915; Austria: 582 to 688). The majority of patients are migrants, according to the Federal Office of Public Health (FOPH). The number of TB deaths in Switzerland is less than ten per year.
In Europe, adults are predominantly affected by tuberculosis, men more than women. In contrast, children often fall ill in countries with a high TB rate. There are many more infected people than sick people. In more than 90 percent of all people infected with TB bacteria, the body’s own immune system is able to keep the pathogens in check or fight them so successfully that no symptoms of the disease appear.
Tuberculosis: Causes and risk factors
By far the most common tuberculosis pathogens are rod-shaped bacteria, also known as tubercle bacilli. They come from the mycobacteria family and mostly belong to the species Mycobacterium tuberculosis.
If TB bacteria get into your body, your immune system tries to fight them with a two-pronged strategy. On the one hand, immune cells encircle the pathogens and form a capsule (a tuberculoma) with them. This is to protect the surrounding tissue. The second strategy: In the center of such a capsule-like cell formation( called agranuloma ), specialized scavenger cells(macrophages) take in bacteria in order to destroy them.
If the body’s own defenses succeed in encapsulating the pathogens and preventing them from breaking out, calcification and scarring of the tissue will eventually occur. It can often still be seen on x-rays years later. If the immune system does not succeed in this process and the patient coughs up heavily infected (infectious) mucus, this is open tuberculosis. It is contagious.
A weakened immune system in particular is often unable to defeat the bacteria. Another reason why the defense against TB bacteria is not always successful is that they are very robust and can survive passively in the macrophages for a long time. A (latent) tuberculosis that has been kept in check can still break out months or years later.
Pulmonary tuberculosis. Chest X-ray: interstitial infiltration in the left upper lung due to Mycobacterium tuberculosis infection
The higher the number of inhaled bacteria, the greater the risk of contracting tuberculosis. The more of these pathogens are present in a room and the longer you are exposed to them, the more likely you are to become infected. The situation is different if other organs are affected rather than the lungs, such as the kidneys, pleura, bones or joints. These forms of tuberculosis, which are rare anyway, are almost impossible to catch – unless you touch someone who has a wound or other open skin area containing TB bacteria.
If you have been in contact with someone who has been successfully treated for tuberculosis for three weeks or longer, it is very likely that this patient is no longer infectious.
Symptoms: Tuberculosis
The mycobacteria that cause TB can affect any organ, but in around 70 percent of all cases registered in Switzerland it is the lungs. All forms of tuberculosis usually progress slowly, and the possible symptoms are usually rather mild at the beginning. They include:
- Fever
- General malaise
- night sweats
- Lack of appetite
- Weight loss
In addition, pulmonary tuberculosis often occurs:
- Cough
- Sputum (mucus)
- Chest pain
Important note: If you have bloody sputum or a cough lasting longer than three weeks, you must visit us.
The possible symptoms of organ tuberculosis:
- Gastrointestinal complaints (with intestinal TB)
- Nodules, thickening and other skin changes (with skin and lymph node TB)
- Shortness of breath (with lymph node TB, the swelling of which constricts the bronchi)
- Nausea, vomiting, stiff neck (in the case of tuberculous meningitis)
How long it takes for the first signs of tuberculosis to appear after infection can vary greatly.
Older patients typically develop fewer symptoms, while children often suffer from prolonged fever or delayed development. There are no clear symptoms that speak exclusively for tuberculosis; the same symptoms could also be seen in neoplastic diseases or autoimmunological diseases, for example. It is therefore initially difficult to make a clear diagnosis of tuberculosis.
Tuberculosis: Diagnosis with us
As the symptoms of tuberculosis are often only mild at the beginning of the disease and do not differ from those of other diseases (such as influenza), the diagnosis of tuberculosis is difficult to make. First of all, we will ask you about your personal medical history (anamnesis): Since when have you had which symptoms? Is there or was there TB in your immediate vicinity? Any existing risk factors will also be discussed in this first meeting. These include: severe chronic illnesses, a possible HIV infection, the use of immunosuppressive drugs (they weaken the effect of the immune system).
In order to be able to make a reliable diagnosis, the TB pathogens must be detected with a laboratory test.
- A bacteriological analysis under the microscope (usually of coughed up secretions) should determine whether pathogens are present. If so, it is often possible to determine whether the bacteria are TB bacteria by DNA analysis.
- A sample of these pathogens is taken to a laboratory where a bacterial culture is created (the pathogens are cultivated and multiply). Once the desired quantity has been produced, it can be determined whether certain drugs are effective against these pathogens.
- In the tuberculin test, killed TB bacteria are injected under the skin. If a skin reaction (swelling, redness) appears after two to three days, the test is positive. However, it only indicates that the body has had contact with mycobacteria in the past and has now produced defense cells – the tuberculin test is not proof of a current tuberculosis infection.
- The test procedure for adult patients is often an interferongamma test (interferon gamma release assays, IGRA for short). In principle, it works like a tuberculin skin test, but has the advantage that reactions only occur with those mycobacteria that cause tuberculosis (name of the bacterial species: Mycobacterium tuberculosis). However, even this test cannot indicate whether active tuberculosis is present.
- An X-ray examination (often in conjunction with computer tomography, CT) can visualize tuberculosis foci in the lungs. X-rays also show the stage of the disease.
Tuberculosis: Prevention, early detection, prognosis
If you want to prevent contracting tuberculosis, there is only one theoretical way: avoid contact with people with active tuberculosis. Also, do not stay in a room where a person with open TB has recently been. Of course, this can rarely be checked in everyday life and is impractical.
There is also a vaccination against tuberculosis (called BCG vaccination). However, the Swiss Vaccination Plan 2020 published by the Federal Office of Public Health only recommends this vaccination for newborns and infants who are younger than 12 months and have an increased risk of infection. These are „infants whose parents come from a country with a high incidence of tuberculosis“ (incidence is the new occurrence of a disease). The BCG vaccination is not effective in adults.
Course and prognosis of tuberculosis
The incubation period after infection is months to years. Short incubation periods are typical in young children and in people with a weakened immune system. Adults usually experience the symptoms of tuberculosis within two years. In a small proportion of infected people, TB can break out much later. In extreme cases, even after more than a decade.
How the disease progresses depends above all on when it is diagnosed and how it is treated. If the following three conditions are met, there is a good chance that the tuberculosis will heal without leaving any permanent damage:
- The diagnosis is made early.
- The therapy starts early.
- The therapy lasts long enough.
If the immune system of a sick person is weakened (for example after an HIV infection) or if the tuberculosis remains undetected for too long, the course is usually less favorable. Lungs or other organs affected by TB bacteria can then be severely damaged.
Tuberculosis: effective treatment
If you have tuberculosis, you will be given four different drugs. All four are antibiotics (in this case also called antituberculotics). Depending on the active ingredient, the aim is to prevent the TB bacteria from multiplying and spreading or to kill the pathogens directly. Pulmonary tuberculosis (by far the most common form of TB) is usually treated initially with the following active substances:
- Isoniazid
- Rifampicin
- Ethambutol
- Pyrazinamide