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Besides HIV/AIDS and malaria, tuberculosis (TB) is one of the most common infectious diseases worldwide. Although the number of new TB infections throughout the world decreases by 2 per cent per year, in 2017 around 1.6 million people died from TB– often due to inadequate treatment. People infected with HIV are particularly vulnerable to TB. They have a 20-30 per cent higher risk of acquiring TB, the majority of these infections being fatal.
Transmission, symptoms, course of the disease
Causative agent of TB infections is Mycobacterium tuberculosis. The bacterium is almost exclusively transmitted through the air and only from human to human. Particularly when sneezing or coughing, infected people release smallest droplets (diameter < 5 µm) carrying the pathogen, which are then inhaled by other people. Normally, only patients with open (pulmonary-positive) tuberculosis pose a risk of infection: in this case the focus of the disease has access to the respiratory tract through which the pathogen can reach the environment3.
On average, the incubation period is six to eight weeks after infection. However, only between five and ten per cent of those infected develop a tuberculosis that needs to be treated. In the remaining cases, the body can combat the mycobacteria and contain the infection permanently (latent tuberculosis infection, LTBI). Whether TB is transmitted depends on the extent (closeness, frequency and length) of the contact to TB patients. Also, the amount and virulence (extent of the pathogenicity) of the pathogen as well as the immune response of the contact person plays a role.
In principle, TB can affect every organ. In 80 per cent of the cases, however, it affects the lung. If symptoms occur, they mostly include coughing with or without sputum. Only in individual cases, the sputum is bloody. Occasionally, infected people complain about chest pain and shortness of breath. Further tuberculosis symptoms include fatigue, weight loss, general weakness and are similar to those of an influenza infection3.
When treated appropriately, patients are no longer infectious two to three weeks after the onset of treatment. However, in case of a resistant TB or a high amount of the pathogen in the sputum, the infectious time might be increased.
Multidrug-resistant tuberculosis MDR-TB and XDR-TB
According to WHO estimates, a total of 558 000 people contracted rifampicin-resistant tuberculosis (RR-TB) in 2017 that cannot be treated with the most effective first-line tuberculostatic agent rifampicin. 457 560 (82 %) of these cases turned out to be multidrug-resistant TB (MDR-TB)1. The pathogens of an MDR-TB are resistant to two or more first-line tuberculostatic agents, such as isoniazid and rifampicin. If the TB pathogens are resistant to all first-line tuberculostatic agents and, additionally, to second-line tuberculostatic agents, one speaks of XDR-TB (extensively drug-resistant tuberculosis). According to WHO estimates, 8.5 per cent of the new MDR-TB cases in 2017 involved XDR-TB2.
Worldwide, only 55 per cent of patients suffering from MDR-TB and 34 per cent of patients suffering from XDR-TB are treated successfully. Therefore, the WHO engages in improved test methods and more effective treatments. Since 2016, they established a shortened treatment using bedaquiline or delamanid – currently 62 and 42 countries apply the new treatment.
Isolation measures and room ventilation
Rapid detection, quick isolation and treatment of patients is the onset to control TB3. Isolation rooms should have own bathrooms. Infected persons should have single rooms and be urged not to leave the room if possible, to prevent superinfections. Only in individual cases, a cohort isolation is worth considering – e.g. in case of a direct chain of infection (mother and child). In case the room needs to be left, a mouth-nose protector should be used.
To prevent the spread of TB pathogens to other hospital areas through the air, it is essential to ventilate the isolation room adequately. high-efficiency particulate air (HEPA) filters. For the latter, isolation rooms need to have a negative pressure, which is to be checked every day4. The air should be exchanged at least 12 times per hour.
PPE and face mask
When taking care of contagious TB patients, FFP2-masks should always be worn, since they protect the staff against inhaling the pathogenic aerosols. One needs to ensure that the mask fits accurately4. According to basic hygiene, protective coats and gloves should be worn, if contact with potentially infectious material is expected (especially when performing e.g. bronchoscopies, in- and extubations).
Hand and surface disinfection
Hand disinfection is to be carried out following the WHO’s 5 Moments. Moreover, the Deutsche Zentralkommittee zur Bekämpfung der Tuberkulose (DZK; German Central Committee for the Control of Tuberculosis) explicitly emphasizes that hand disinfection needs to be performed before putting on gloves.
As TB is transmitted through the air, surfaces are disinfected as usual. This includes routine-disinfection of surfaces in the immediate patient surroundings and targeted disinfection of visibly contaminated surfaces. Surface disinfectants with proven mycobacterial spectrum of activity are to be used.
