When referring to tuberculosis, a distinction must first be made between a latent tuberculosis infection (LTBI) and active tuberculosis. People with LTBI do not have symptoms and are not contagious but may develop active tuberculosis under certain conditions. In around 80 % of cases, active tuberculosis affects the lungs, but it can also attack other organs such as liver, spleen or kidneys.
Only people with active pulmonary tuberculosis can infect other people. The term "open tuberculosis" is used if the site of infection is associated with the airways.
The World Health Organization (WHO) estimates that approximately 10 million people contract tuberculosis every year, and around 1.5 million people die every year as a result. In 2019, the most infections worldwide were recorded in Southeast Asia (44 %), Africa (25 %), the Western Pacific region (18 %) and the Eastern Mediterranean (8.2 %). The figures in America (2.9 %) and Europe (2.5 %) were significantly lower. At country level, India was the worst affected country in 2019 with 26 % of all tuberculosis cases.
Although it has been possible to reduce the number of deaths from tuberculosis by as much as 14 % from 2015 to 2019, antibiotic-resistant pathogens are still a major cause for concern.
The most common cause of tuberculosis infection in humans is mycobacteria of the species Mycobacterium tuberculosis. The M. tuberculosis complex also includes other species of mycobacteria, although they only play a minor role in the incidence of the disease in humans. Moreover, people are the only reservoir for M. tuberculosis. The disease can only be transmitted by those infected with open pulmonary tuberculosis. Infection occurs primarily via droplets and aerosols, which are inhaled.
Following contact with the pathogen, most of those infected (85-95 %) only experience an asymptomatic primary infection and do not fall ill with tuberculosis requiring treatment throughout their life. In otherwise healthy people, the immune system can usually combat the bacteria or encapsulate infected areas. These people have LTBI, which can, however, develop into active tuberculosis (reactivation). The risk of active tuberculosis (both primary and reactivated) is particularly high in immunocompromised people (particularly those with HIV) and people with risk factors such as smoking, diabetes, malnutrition, or high alcohol consumption. Even though most people develop active tuberculosis within the first two years after the initial infection, reactivation can still occur decades later.
The cardinal symptom of pulmonary tuberculosis is a cough with or without sputum, which can also be bloody, although this is less common than usually assumed. In addition, chest pain and respiratory distress may occur as well as various non-specific general symptoms. Pulmonary tuberculosis does not have a clear set of symptoms, which makes it significantly harder to diagnose.
The symptoms of tuberculosis in other organs differ according to the location. In rare cases – primarily in immunocompromised people and in infants and toddlers – the pathogens can even spread via the blood and attack other organs as well as the brain. In this case, usually severe disease symptoms occur (high fever, respiratory disorder, etc.).
Active tuberculosis is always treated with a combination of different antibiotics over several months. This approach is used to prevent selection of resistant bacteria and capture dormant pathogens. Antibiotic resistance is an obstacle to successful treatment. While the rate of resistance is low in people born in Germany, it occurs more frequently in people born in the Commonwealth of Independent States (CIS), for example.
People with LTBI can receive preventive treatment with antibiotics if the risk of active tuberculosis is high.
WHO takes three main approaches to preventing tuberculosis: preventing the development of active infections from LTBI, preventing transmission by means of infection control and performing vaccinations.
Preventive treatment plays a significant role, particularly in people with HIV, household contacts of those with active pulmonary tuberculosis and high-risk groups.
In addition to diagnosing and isolating those infected, cough etiquette, hand hygiene, respiratory protection and room ventilation are among the measures recommended to prevent transmission ofM. tuberculosis.
Tuberculosis vaccination is based on a live attenuated vaccine with Bacillus Calmette-Guérin, another pathogen of theM. tuberculosiscomplex. However, it has only limited efficacy und is not recommended in countries with decreasing incidence such as Germany.
Sources:
Federal Ministry of Health.Mycobacterium tuberculosis – Stellungnahmen des Arbeitskreises Blut des Bundesministeriums für Gesundheit [Mycobacterium tuberculosis – statements from the Blood Working Gorup of the Federal Ministry of Health]. Federal Health Gazette 2018; 61: 100–115. (last reviewed on 20 January 2021)
Robert Koch Institute.RKI-Ratgeber Tuberkulose [RKI (Robert Koch Institute) guide on tuberculosis]. As at: 21 February 2013.
World Health Organization.WHO guidelines on tuberculosis infection prevention and control: 2019 update. (last reviewed on 20 January 2021)
World Health Organization.Tuberculosis. (last reviewed on 20 January 2021)
World Health Organization.Global Tuberculosis Report 2020. (last reviewed on 20 January 2021)
