7.6.3: Drug-resistant Tuberculosis
Another very concerning example is that of drug-resistant tuberculosis (TB). The bacterium Mycobacterium tuberculosis causes disease most commonly in the lungs, although it can affect other organ systems. TB is spread through respiratory droplets, and develops slowly - only about 5-10% of those infected will actually develop the disease and become contagious - often due to a depressed immune system (often caused by HIV infection). Yet, the global disease burden is still high. It is estimated that 10 million cases of the disease happen every year worldwide, causing 1.5 million deaths (World Health Organization: WHO, 2019).
When the TB bacteria cause active disease, this can happen within 2 years or even decades after infection. Often other factors that depress the immune system are involved, such as co-infections (e.g. HIV), malnutrition, crowded housing, and lack of access to medical care. Mycobacterium tuberculosis has a thick, fatty surface that is difficult for the human immune system to break down, so white blood cells will typically envelope the bacteria instead - creating calcified “tubercles”. If the bacteria escapes these tubercles, then the bacteria can proliferate, causing active disease - mostly in the lungs but also in several other organ systems such as the central nervous system (CrashCourse, 2024).
Thanks to the development of antibiotics in the 1950s and 60s, we do have treatments and can cure this disease. Although TB has been eliminated from several countries and has the potential to be eradicated around the world, drug-resistant strains make this goal much more challenging. Certain factors increase the risk of drug-resistant TB, including:
- A full course of TB drug treatment is not completed, doses are missed or delayed
- High-quality drugs are not available
- The wrong drugs are prescribed (CDCTB, 2022)
In developing countries, other social determinants of health (SDOH) also influence these risk factors. For example, pharmaceutical companies are driven by profit incentives to develop and produce drugs, and since TB has been eliminated in many wealthy countries, there is less production of these drugs. Modern TB tests and drugs are (unnecessarily) expensive, and in order to ensure “compliance”, patients are often required to visit a clinic daily, or live in an inpatient facility for months. For someone already living in poverty, and with a severe illness, transportation and physical disability can be large barriers in getting treatment. Combine this with other SDOH such as access to nutrition, drinking water, and quality housing, and treating TB - especially drug-resistant TB - becomes much more challenging. Increases in the accessibility of testing, treatment, healthcare staff, and addressing barriers to treatment are all necessary if we want to eliminate TB (CrashCourse, 2024).