Tuberculosis (TB)

Tuberculosis is a bacterial infectious disease that predominantly affects the lungs. It is still one of the most common infections worldwide, with around 10 million cases each year. Treatment of TB is protracted, largely because tuberculosis bacteria have become resistant, i.e., insensitive, to many drugs.

At a glance

  • Tuberculosis is an infectious disease caused by bacteria.
  • It is transmitted from person to person through the air.
  • Tuberculosis develops in only 5 to 10% of those infected.
  • Young children and people with an immunodeficiency are most at risk.
  • Treatment lasts 6 months and is usually successful.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Tuberkulose: Eine Röntgenaufnahme des Brustkorbs. Eine rot-schwarze Verfärbung im linken Lungenflügel weist auf eine Tuberkuloseinfektion hin.

What is tuberculosis?

Tuberculosis is an infectious disease that typically affects the lungs in particular. However, other organs can also be affected. It is caused by tuberculosis bacteria that are transmitted from person to person in tiny droplets through the air when they speak, sneeze, cough or sing.

It is estimated that around one quarter of the world’s population is infected with the tuberculosis pathogen. However, most of them barely even notice because the body manages to fight the bacteria successfully or encapsulate them, thereby restricting them permanently. This is known as a latent tuberculosis infection. The bacteria can survive in the body for years. The disease develops in only 5 to 10% of those infected.

Tuberculosis can start with non-specific symptoms such as loss of weight, slightly raised body temperature, night sweats and coughing. The disease was formerly known as consumption due to the weight loss it causes.

The treatment of tuberculosis is a lengthy process. This is because tuberculosis bacteria are very resistant and they exist in various stages of growth, which means that doctors have to use a range of different drugs.

Information about tuberculosis that laypeople can understand is also provided by the German Agency for Quality in Medicine (Ärztliches Zentrum für Qualität in der Medizin) and the German Central Committee against Tuberculosis (Deutsches Zentralkomitee zur Bekämpfung der Tuberkulose).

What are infectious diseases?

The video below looks at when doctors talk about an infectious disease, which pathogens trigger infectious diseases, and how they are transmitted.

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What are the symptoms of tuberculosis?

The lungs are most commonly affected, but sometimes other organs are impacted too. The first time someone is infected, they may have no symptoms.

Infection without symptoms

In around 90% of those infected, the immune system is able to fight and encapsulate the tuberculosis bacteria. The encapsulated structures are called tuberculoma. The bacteria can survive in these tuberculomas for years. This is known as latent tuberculosis.

Infection with symptoms

When the disease develops, it usually does so within the first one to two years. However, it is also possible for this to occur only decades after the infection. The lungs are affected in over 70% of those with the infection who show symptoms. In addition, there are also foci of disease (i.e., infection sites) in the lymph nodes, pleura, kidneys and the lower urinary tract and, in rare cases, in bones, meninges and other organs.

The disease usually starts with a mild fever, weakness, unexplained weight loss and night sweats. The typical symptom of tuberculosis of the lung is coughing with or without sputum (thick mucus/phlegm), which lasts for a long time and, in rare cases, may be bloody. Chest pain and difficulty breathing also occur occasionally.

Other possible general symptoms are:

  • Poor general health
  • Loss of appetite
  • Fatigue

An initial infection with symptoms (primary tuberculosis) mainly occurs when the immune system is already weakened by other factors. Young children and people with HIV are most often affected. Even if the initial infection has been well encapsulated by the body, an immune deficiency can re-activate “dormant” bacteria in the tuberculomas and lead to illness (postprimary tuberculosis).

In rare cases, e.g. in a person with a weakened immune system, small foci (sites) of infection can be spread throughout the body. In addition, (sepsis) may occur, where the bloodstream becomes flooded with pathogens.

Important: Any cough lasting more than three weeks should always be investigated by a doctor. If a person coughs up blood, they need to be seen by a doctor without delay.

What causes tuberculosis?

The cause of TB is an infection with bacteria that is transmitted from one person to another.

Tuberculosis bacteria

TB is triggered by rod-shaped bacteria from the Mycobacteria family. The most common pathogen to trigger the infection is Mycobacterium tuberculosis, which was discovered by Robert Koch. There are also other Mycobacteria that can cause TB, including Mycobacterium bovi (which causes bovine TB) and Mycobacterium africanum.

Person-to-person infection

TB infections are normally spread by people who have what is known as “open” tuberculosis. “Open” in this sense means that the pathogens have spread to their airways and are released in the tiny droplets (aerosols) contained in the air that they breathe out, in particular when coughing and sneezing. In this way, they can infect other people through the air.

If a person is infected with TB in organs other than the lungs, the risk of infecting other people through social contact is extremely low.

Infection from unpasteurized milk

TB can, in principle, be transmitted via unpasteurized milk. However, most cattle in this part of Europe are free of TB and so this risk is insignificant in Germany.

How contagious are people infected with TB?

People with open tuberculosis are most infectious if bacteria are visible when their phlegm is examined under a microscope. The disease is less contagious if the bacteria can only be detected after they are grown in a suitable culture or by means of molecular biology tests. In children under 10 years of age, it is often impossible to detect the bacteria under a microscope. In addition, children are less contagious than adults because their cough strength is weaker.

Who is particularly susceptible to tuberculosis?

There are certain groups of people and patients who are particularly at risk of developing tuberculosis.

These include:

  • Close contacts of people with open tuberculosis
  • People with poorly treated tuberculosis
  • Small children
  • People with immune deficiency, such as those with an HIV infection
  • Patients who are receiving immunosuppressant treatment, for example, organ recipients or people with rheumatic disorders
  • People with an alcohol or drug dependency
  • Homeless people
  • People with chronic conditions, such as diabetes mellitus
  • People with silicosis, a lung condition caused by dust-containing silica and often occurring in those working in the construction and ceramics industries

How common is tuberculosis?

Tuberculosis is very common all over the world. It can spread easily, especially in areas where large numbers of people are infected with HIV. Their immune deficiency puts them at an increased risk of contracting the disease. In addition, treatment in these areas is often inadequate and the tuberculosis bacteria are increasingly resistant to the drugs (antibiotics) used.

Prevalence worldwide

Around 10 million people contract tuberculosis worldwide every year, and around 1.5 million die as a result. This means that tuberculosis is the world’s most common deadly bacterial infectious disease in adolescents and adults. It is one of the most common causes of death in people with HIV.

The situation is particularly problematic in sub-Saharan Africa. Around 86% of all people with a new TB infection live in Africa, Southeast Asia and the Western Pacific Region.

Prevalence in Europe

Europe accounts for around 3% of all new cases of tuberculosis worldwide, with significant regional differences. In Western European countries, fewer than 15 people per 100,000 inhabitants a year develop TB, while this figure is around 20 in the Balkan states and over 100 in Eastern Europe.

In most Western European countries, the numbers have been falling continuously for many years. In Eastern Europe, the situation is made more difficult by increasing regional drug resistance, i.e., insensitivity of the tuberculosis bacteria to antibiotics.

Prevalence in Germany

For 2019, 4,791 cases of tuberculosis were reported to the Robert Koch Institute in Germany – that corresponds to almost 6 cases per 100,000 inhabitants.

There were 4,791 cases of tuberculosis in Germany in 2019.

People who are born in countries where tuberculosis is still very common are most affected. As about 60% of tuberculosis cases are cases of open (and contagious) pulmonary tuberculosis, the occurrence of TB infections is monitored by the local health authorities.

What is the outlook for a tuberculosis infection?

People with healthy immune systems

Only some of those infected actually develop tuberculosis that needs treatment. The figure is around 5 to 10% for adults and adolescents with a normal immune system.

The risk of disease is at its highest in the first two years after infection.

Only 5 to 10% of those infected with tuberculosis actually go on to develop the disease.

People with impaired immune systems

Active tuberculosis can soon develop after the infection, especially in people with an immune deficiency. In these people, the bacteria can spread more easily to other organs via the lymphatic pathways and/or the bloodstream. In addition, if their immune system is weakened – for example due to taking certain drugs – people can still develop tuberculosis decades after the initial infection (this is known as reactivation).

Infants and young children

Infants and young children are particularly at risk of infection and of becoming ill because their immune systems are not yet fully developed.

How can tuberculosis be prevented?

In Germany, people were previously vaccinated against tuberculosis. However, as of 1998, this has not been recommended by the Standing Committee on Vaccination (STIKO) at the Robert Koch Institute in Germany. There are several reasons for this:

  • The vaccination is only useful for infants in regions with a high infection risk.
  • In Germany, the risk of infection is low.
  • As it is a life-long vaccine, there is an increased risk of side effects.

In some countries, vaccination is required if the person wants to stay there for an extended period. This should be discussed with a family doctor.

How do vaccinations work?

The video below explains how a vaccination works.

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How is tuberculosis diagnosed?

Diagnostic tests are carried out at the beginning of treatment and during treatment to monitor its success. Typically, sputum from the lungs or lung secretion is examined. Depending on which organs are affected, the pathogens can also be detected in gastric juice, urine, cerebrospinal fluid or other fluid and tissue samples.

The tuberculosis bacteria can be directly detected under the microscope or be replicated and analyzed in a bacterial culture. If the bacteria can be seen under a microscope, this means that the patient is particularly contagious. It is also possible to detect bacterial genetic material. It is important to determine the sensitivity or resistance of bacteria to antibiotics so that doctors can choose effective medication.

In addition to detecting the pathogen, diagnosing tuberculosis always involves taking an X-ray of the lungs. This is so that doctors can determine whether the patient has infectious pulmonary tuberculosis and whether the treatment is successful. A CT scan, i.e., a layered X-ray, can be performed to assess changes in the lungs more accurately.

To detect a latent tuberculosis infection, small amounts of bacterial components are injected into the skin and the skin’s reaction is assessed. This tuberculin test can detect an infection with bacteria from around 6 to 8 weeks after contact. A test known as the interferon gamma test serves the same purpose, but is carried out on a blood sample and is less sensitive to interference than the skin test.

How can tuberculosis be treated?

The treatment of tuberculosis is a lengthy process. A major problem is presented by the fact that tuberculosis bacteria have become resistant to many antibiotics. As a result, these drugs are no longer effective.


A tuberculosis infection is always treated with several drugs at the same time. Tuberculosis bacteria are very resistant and are found in the body in different forms. Depending on their environment, they replicate quickly or slowly or enter a dormant state. Various drugs have different mechanisms of action, and together they fight all stages of the bacteria at the same time. There are always a few pathogens that are naturally resistant to individual drugs.

Four standard drugs with the following active ingredients are available to treat tuberculosis and these are administered at the same time:

  • Isoniazide
  • Rifampicin
  • Ethambutol
  • Pyrazinamide

There are also drugs known as secondary or reserve drugs that are used in the event of resistance or intolerances.

Standard treatment

Children and adults usually first receive a combination of four over at least 6 months, followed by a combination of two of the above antibiotics. The treatment can lead to various manageable side effects, including skin rashes, vision problems and impaired liver function. Patients who respond to treatment are usually no longer contagious within 2 to 3 weeks.

Important: Even if patients no longer have any symptoms after a few weeks, treatment should always be continued for at least 6 months. Otherwise, the infection can flare up again and be more difficult to treat because the drugs may no longer work.

Problem – resistance to drugs

It is very important to monitor treatment continuously so that it is immediately apparent if the patient cannot tolerate the drug or it is not working (resistance). The treatment may then have to be changed and possibly extended. If there is adverse resistance, treatment may take up to 20 months with more medication.

Multiresistant tuberculosis, where there is simultaneous resistance to the two main drugs isoniazide and rifampicin, is particularly significant. By now, some tuberculosis bacteria have also developed resistance to some reserve drugs.

The resistance rates in Germany have remained stable at a low level in recent years. However, they may be higher for people born outside of Germany. The highest proportion of multiresistant tuberculosis is found in people with the disease from countries of the former Soviet Union.

Supporting treatment

Stopping treatment prematurely can lead to a relapse or to other tuberculosis bacteria becoming resistant to drugs. This is why it is important to support those affected and not marginalize them. Family and friends play an important role in this. Contact is usually possible and desirable provided that a suitable full face mask is worn.

Digital applications such as apps or websites can also be used to support treatment. Some can also help patients take the medication they need on a daily basis.

An app providing information in over 40 languages is available on the Explain TB website.

Practical tips for patients undergoing treatment for TB is provided by the German Agency for Quality in Medicine (Ärztliches Zentrum für Qualität in der Medizin) and the German Central Committee against Tuberculosis (Deutsches Zentralkomitee zur Bekämpfung der Tuberkulose).

What is everyday life like with tuberculosis?

Tuberculosis requiring treatment must be reported to the local health authority. Those with open tuberculosis are initially isolated in a hospital for as long as they are contagious. Once they are no longer excreting any tuberculosis bacteria in their phlegm, they can usually continue their treatment at home. People in contact with those with the disease are also examined and may receive preventive treatment.

People who have or are suspected of having a contagious TB infection are not permitted to work in community facilities such as kindergartens, schools or hospitals. Their treating physician, together with the public health authority, will determine when they will be permitted to do so. Before this can happen, the disease must no longer be contagious and the treatment must be well tolerated.

Where can I find information about tuberculosis?

You can find useful information about tuberculosis in the information leaflet for patients and their relatives available from the German Central Committee against Tuberculosis (Deutsches Zentralkomitee zur Bekämpfung der Tuberkulose).

Reviewed by the German Respiratory Society (Deutsche Gesellschaft für Pneumologie und Beatmungsmedizin e.V.)

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