Tuberculosis (Human and Animal)
Primary reference(s)
WHO, 2020. Tuberculosis. World Health Organization (WHO). Accessed 3 November 2020.
Additional scientific description
Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs. Tuberculosis is curable and preventable. It is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected (WHO, 2020).
About one-quarter of the world’s population has latent tuberculosis infection (LTBI), which means people have been infected by TB bacteria but are not (yet) ill with the disease and cannot transmit the disease. However, they have a 5–15% lifetime risk of falling ill. Persons with compromised immune systems, such as people living with human immunodeficiency virus (HIV), malnutrition or diabetes, are at higher risk. People living with HIV are 19 times more likely to develop active TB than people without HIV. HIV and TB form a lethal combination, each speeding the other’s progress (WHO, 2020).
The symptoms of active TB are coughing (sometimes with sputum or blood), chest pains, weakness, weight loss, fever, and night sweats. When a person develops active TB, the symptoms may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others (WHO, 2020).
Diagnostic tests for tuberculosis disease include sputum smear microscopy (a long-used method that allows visualisation of the bacteria, many countries rely on it), rapid molecular tests (endorsed by the World Health Organization [WHO]) and culture-based methods; the latter take up to 12 weeks to provide results but remain the reference standard. TB that is resistant to first-line and second-line anti-TB drugs can be detected using rapid tests, culture methods and sequencing technologies. However, TB is particularly difficult to diagnose in children (WHO, 2020).
Multidrug-resistant tuberculosis (MDR-TB) is a form of drug-resistant TB caused by bacteria that do not respond to the two most powerful first-line anti-TB drugs – rifampicin and isoniazid. MDR-TB is treatable and curable by using second-line treatment options, which are limited and require extensive chemotherapy with medicines that are expensive and toxic. Extensively drug-resistant TB (XDR-TB) is a more serious form of MDR-TB caused by bacteria that do not respond to the most effective second-line anti-TB drugs, often leaving patients without any further treatment options (WHO, 2020).
In 2019, MDR-TB remains a public health crisis and a health security threat. A global total of 206,030 people with multidrug- or rifampicin-resistant TB (MDR/RR-TB) were detected and notified in 2019, a 10% increase from 186,883 in 2018. About half of the global burden of MDR-TB is in three countries – India, China and the Russian Federation (WHO, 2020).
The WHO has published information about case-definitions and classification (WHO, 2014) as well as guidelines for surveillance of drug resistance in tuberculosis (WHO, 2015).
Metrics and numeric limits
According to the WHO (2020):
- TB occurs in every part of the world and is one of the top ten causes of death and the leading cause from a single infectious agent (above HIV/AIDS) worldwide.
- A total of 1.4 million people died from TB in 2019 (including 208,000 people with HIV).
- In 2019, an estimated 10 million people fell ill with TB worldwide: 5.6 million men, 3.2 million women and 1.2 million children. TB is present in all countries and age groups. But TB is curable and preventable.
- Child and adolescent TB is often overlooked by health providers and can be difficult to diagnose and treat.
- In 2019, the 30 high TB burden countries accounted for 87% of new TB cases. Eight countries account for two-thirds of the total, with India leading the count, followed by Indonesia, China, the Philippines, Pakistan, Nigeria, Bangladesh and South Africa.
- Globally, TB incidence is falling at about 2% per year and between 2015 and 2019 the cumulative reduction was 9%. This was less than half way to the End TB Strategy milestone of 20% reduction between 2015 and 2020.
- An estimated 60 million lives were saved through TB diagnosis and treatment between 2000 and 2019.
Key relevant UN convention / multilateral treaty
International Health Regulations (2005), 3rd ed. (WHO, 2016).
Examples of drivers, outcomes and risk management
WHO recommended strategies for TB prevention include: systematic screening and preventative treatment programmes for LTBI for high-risk population groups in order to reduce the risk of progression from LTBI to active TB; vaccination of children with the bacille Calmette-Guérin (BCG) vaccine (WHO, 2019); infection control measures in health facilities; and social protection, poverty alleviation and action on other determinants of TB.
The BCG vaccine is the only licensed vaccine for TB but is only effective in children. There is currently no vaccine that is effective in preventing TB in adults (WHO, 2019).
The main challenges in treatment of TB disease are the duration and complexity of drug regimens, both of which affect adherence; adverse drug reactions, especially for the drugs used to treat drug-resistant TB; and the absence or limited availability of paediatric drug formulations for second-line treatment (WHO, 2020).
Risk factors for MDR-TB and XDR-TB include: low adherence of patients to treatment, due to length and toxicity of regimen; poor quality or unavailable anti-TB drugs; and incorrect prescription of anti-TB medicines by health care providers (WHO, 2019).
TB treatment for people co-infected with HIV is further complicated by drug–drug interactions between anti-TB drugs and antiretroviral therapies, and by cumulative drug toxicities (WHO, 2019).
There is a pressing need for anti-TB regimens that are more effective, more affordable and nontoxic, and that shorten the duration of treatment (WHO, 2020).
Ending the tuberculosis epidemic by 2030 is among the health targets of the Sustainable Development Goals of UN Agenda 2030 (WHO, 2020).
References
WHO, 2014. Definitions and reporting framework for tuberculosis – 2013 revision. World Health Organization (WHO). Accessed 16 December 2019.
WHO, 2015. Guidelines for surveillance of drug resistance in tuberculosis, 5th edition. World Health Organization (WHO). Accessed 16 December 2019.
WHO, 2016. International Health Regulations (2005), 3rd ed. World Health Organization (WHO). Accessed 3 October 2020.
WHO, 2019. Global Tuberculosis report 2019. World Health Organization (WHO). Accessed 16 December 2019.
WHO, 2020. Tuberculosis. World Health Organization (WHO). Accessed 3 November 2020.