- Tuberculosis (TB) is a top infectious disease killer worldwide.
- In 2014, 9.6 million people fell ill with TB and 1.5 million died from the disease.
- Over 95% of TB deaths occur in low- and middle-income countries, and it is among the top 5 causes of death for women aged 15 to 44.
- In 2014, an estimated 1 million children became ill with TB and 140 000 children died of TB.
- TB is a leading killer of HIV-positive people: in 2015, 1 in 3HIV deaths was due to TB.
- Globally in 2014, an estimated 480 000 people developed multidrug-resistant TB (MDR-TB).
- The Millennium Development Goal target of halting and reversing the TB epidemic by 2015 has been met globally. TB incidence has fallen by an average of 1.5% per year since 2000 and is now 18% lower than the level of 2000.
- The TB death rate dropped 47% between 1990 and 2015.
- An estimated 43 million lives were saved through TB diagnosis and treatment between 2000 and 2014.
- Ending the TB epidemic by 2030 is among the health targets of the newly adopted Sustainable Development Goals.
Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs. Tuberculosis is curable and preventable.
TB 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.
About one-third of the world's population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with the disease and cannot transmit the disease.
People infected with TB bacteria have a 10% lifetime risk of falling ill with TB. However, persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.
When a person develops active TB disease, the symptoms (cough, fever, night sweats, weight loss etc.) may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others. People with active TB can infect 10-15 other people through close contact over the course of a year. Without proper treatment, 45% of HIV-negative people with TB on average and nearly all HIV-positive people with TB will die.
Who is most at risk?
Tuberculosis mostly affects adults in their most productive years. However, all age groups are at risk. Over 95% of cases and deaths are in developing countries.
People who are infected with HIV are 20 to 30 times more likely to develop active TB (see TB and HIV section). The risk of active TB is also greater in persons suffering from other conditions that impair the immune system.
One million children (0-14 years) fell ill with TB, and 140 000 children died from the disease in 2014.
Tobacco use greatly increases the risk of TB disease and death. More than 20% of TB cases worldwide are attributable to smoking.
Global impact of TB
TB occurs in every part of the world. In 2014, the largest number of new TB cases occurred in the South-East Asia and Western Pacific Regions, accounting for 58% of new cases globally. However, Africa carried the most severe burden, with 281 cases per 100 000 population in 2014 (compared with a global average of 133).
In 2014, about 80% of reported TB cases occurred in 22 countries. The 6 countries that stand out as having the largest number of incident cases in 2014 were India, Indo¬nesia, Nigeria, Pakistan, People’s Republic of China and South Africa. Some countries are experiencing a major decline in cases, while in others the numbers are dropping very slowly. Brazil and China for example, are among the 22 countries with a sustained decline in TB cases over the past 20 years.
Symptoms and diagnosis
Common symptoms of active lung TB are cough with sputum and blood at times, chest pains, weakness, weight loss, fever and night sweats. Many countries still rely on a long-used method called sputum smear microscopy to diagnose TB. Trained laboratory technicians look at sputum samples under a microscope to see if TB bacteria are present. With 3 such tests, diagnosis can be made within a day, but this test does not detect numerous cases of less infectious forms of TB.
Diagnosing MDR-TB (see Multidrug-resistant TB section below) and HIV-associated TB can be more complex. A new 2 hour test that has proven highly effective in diagnosing TB and the presence of drug resistance is now being rolled-out in many countries.
Tuberculosis is particularly difficult to diagnose in children.
TB is a treatable and curable disease. Active, drug-susceptible TB disease is treated with a standard 6 month course of 4 antimicrobial drugs that are provided with information, supervision and support to the patient by a health worker or trained volunteer. Without such support, treatment adherence can be difficult and the disease can spread. The vast majority of TB cases can be cured when medicines are provided and taken properly.
Between 2000 and 2014, an estimated 43 million lives were saved through TB diagnosis and treatment.
TB and HIV
At least one-third of people living with HIV worldwide in 2014 were infected with TB bacteria. People living with HIV are 20 to 30 times more likely to develop active TB disease than people without HIV.
HIV and TB form a lethal combination, each speeding the other's progress. In 2014 about 0.4 million people died of HIV-associated TB. Approximately one third of deaths among HIV-positive people were due to TB in 2014. In 2014 there were an estimated 1.2 million new cases of TB amongst people who were HIV-positive, 74% of whom were living in Africa.
WHO recommends a 12-component approach of collaborative TB-HIV activities, including actions for prevention and treatment of infection and disease, to reduce deaths.
Standard anti-TB drugs have been used for decades, and resistance to the medicines is widespread. Disease strains that are resistant to a single anti-TB drug have been documented in every country surveyed.
Multidrug-resistant tuberculosis (MDR-TB) is a form of TB caused by bacteria that do not respond to, at least, isoniazid and rifampicin, the 2 most powerful, first-line (or standard) anti-TB drugs.
A primary cause of MDR-TB is inappropriate treatment. Inappropriate or incorrect use of anti-TB drugs, or use of poor quality medicines, can cause drug resistance.
Disease caused by resistant bacteria fails to respond to conventional, first-line treatment. MDR-TB is treatable and curable by using second-line drugs. However second-line treatment options are limited and recommended medicines may not be always available. The extensive chemotherapy required (up to 2 years of treatment) is more costly and can produce severe adverse drug reactions in patients.
In some cases, more severe drug resistance can develop. Extensively drug-resistant TB, XDR-TB, is a form of multi-drug resistant tuberculosis that responds to even fewer available medicines, including the most effective second-line anti-TB drugs.
About 480 000 people developed MDR-TB in the world in 2014. More than half of these cases were in India, the People’s Republic of China and the Russian Federation. It is estimated that about 9.7% of MDR-TB cases had XDR-TB.
WHO pursues 6 core functions in addressing TB.
- Provide global leadership on matters critical to TB.
- Develop evidence-based policies, strategies and standards for TB prevention, care and control, and monitor their implementation.
- Provide technical support to Member States, catalyze change, and build sustainable capacity.
- Monitor the global TB situation, and measure progress in TB care, control, and financing.
- Shape the TB research agenda and stimulate the production, translation and dissemination of valuable knowledge.
- Facilitate and engage in partnerships for TB action.
The WHO End TB Strategy, adopted by the World Health Assembly in May 2014, is a blueprint for countries to end the TB epidemic by driving down TB deaths, incidence and eliminating catastrophic costs. It outlines global impact targets to reduce TB deaths by 90% and to cut new cases by 80% between 2015 and 2030, and to ensure that no family is burdened with catastrophic costs due to TB.
Ending the TB epidemic by 2030 is among the health targets of the newly adopted Sustainable Development Goals. WHO has gone one step further and set a 2035 target of 95% reduction in deaths and a 90% decline in TB incidence - similar to current levels in low TB incidence countries today.
The Strategy outlines 3 strategic pillars that need to be put in place to effectively end the epidemic:
- Pillar 1: integrated patient-centred care and prevention
- Pillar 2: bold policies and supportive systems
- Pillar 3: intensified research and innovation.
The success of the Strategy will depend on countries respecting the following 4 key principles as they implement the interventions outlined in each pillar:
- government stewardship and accountability, with monitoring and evaluation
- strong coalition with civil society organizations and communities
- protection and promotion of human rights, ethics and equity
- adaptation of the strategy and targets at country level, with global collaboration