Tuberculosis, or TB, is an infectious bacterial disease caused by Mycobacterium tuberculosis, which most commonly affects the lungs. It is transmitted from person to person via droplets from the throat and lungs of people with the active respiratory disease.
In healthy people, infection with Mycobacterium tuberculosis often causes no symptoms, since the person's immune system acts to “wall off” the bacteria. The symptoms of active TB of the lung are coughing, sometimes with sputum or blood, chest pains, weakness, weight loss, fever and night sweats. Tuberculosis is treatable with a six-month course of antibiotics.
Infection and transmission
Tuberculosis (TB) is a contagious disease. Like the common cold, it spreads through the air. Only people who are sick with TB in their lungs are infectious. When infectious people cough, sneeze, talk or spit, they propel TB germs, known as bacilli, into the air. A person needs only to inhale a small number of these to be infected.
Left untreated, each person with active TB disease will infect on average between 10 and 15 people every year. But people infected with TB bacilli will not necessarily become sick with the disease. The immune system "walls off" the TB bacilli which, protected by a thick waxy coat, can lie dormant for years. When someone's immune system is weakened, the chances of becoming sick are greater.
· Overall, one-third of the world's population is currently infected with the TB bacillus.
· 5-10% of people who are infected with TB bacilli (but who are not infected with HIV) become sick or infectious at some time during their life. People with HIV and TB infection are much more likely to develop TB.
Global and regional incidence
WHO estimates that the largest number of new TB cases in 2008 occurred in the South-East Asia Region, which accounted for 35% of incident cases globally. However, the estimated incidence rate in sub-Saharan Africa is nearly twice that of the South-East Asia Region with over 350 cases per 100 000 population.
An estimated 1.7 million people died from TB in 2009. The highest number of deaths was in the Africa Region.
In 2008, the estimated per capita TB incidence was stable or falling in all six WHO regions. However, the slow decline in incidence rates per capita is offset by population growth. Consequently, the number of new cases arising each year is still increasing globally in the WHO regions of Africa, the Eastern Mediterranean and South-East Asia.
Estimated TB incidence, prevalence and mortality, 2009
Uncertainty bounds for the table below are available in the Global tuberculosis control 2010 (Table 1, page 5).
Incidence1 | Prevalence 2 | Mortality (excl. HIV) | |||||
WHO region | No. in thousands | % of global total | Rate per 100 000 pop3 | No. in thousands | Rate per 100 000 pop3 | No. in thousands | Rate per 100 000 pop3 |
Africa | 2 800 | 30% | 340 | 3 900 | 450 | 430 | 50 |
The Americas | 270 | 2.9% | 29 | 350 | 37 | 20 | 2.1 |
Eastern Mediterranean | 660 | 7.1% | 110 | 1 000 | 180 | 99 | 18 |
Europe | 420 | 4.5% | 47 | 560 | 63 | 62 | 7 |
South-East Asia | 3 300 | 35% | 180 | 4 900 | 280 | 480 | 27 |
Western Pacific | 1 900 | 21% | 110 | 2 900 | 160 | 240 | 13 |
Global total | 9 400 | 100% | 140 | 14 000 | 164 | 1 300 | 19 |
1 Incidence is the number of new cases arising during a defined period. 2 Prevalence is the number of cases (new and previously occurring) that exists at a given point in time. 3 Pop indicates population. | |||||||
HIV and TB
HIV and TB form a lethal combination, each speeding the other's progress. HIV weakens the immune system. Someone who is HIV-positive and infected with TB bacilli is many times more likely to become sick with TB than someone infected with TB bacilli who is HIV-negative. TB is a leading cause of death among people who are HIV-positive. In Africa, HIV is the single most important factor contributing to the increase in the incidence of TB since 1990.
WHO and its international partners have formed the TB/HIV Working Group, which develops global policy on the control of HIV-related TB and advises on how those fighting against TB and HIV can work together to tackle this lethal combination. The interim policy on collaborative TB/HIV activities describes steps to create mechanisms of collaboration between TB and HIV/AIDS programmes, to reduce the burden of TB among people and reducing the burden of HIV among TB patients.
Drug-resistant TB
Until 50 years ago, there were no medicines to cure TB. Now, strains that are resistant to a single drug have been documented in every country surveyed; what is more, strains of TB resistant to all major anti-TB drugs have emerged. Drug-resistant TB is caused by inconsistent or partial treatment, when patients do not take all their medicines regularly for the required period because they start to feel better, because doctors and health workers prescribe the wrong treatment regimens, or because the drug supply is unreliable. A particularly dangerous form of drug-resistant TB is multidrug-resistant TB (MDR-TB), which is defined as the disease caused by TB bacilli resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. Rates of MDR-TB are high in some countries, especially in the former Soviet Union, and threaten TB control efforts.
While drug-resistant TB is generally treatable, it requires extensive chemotherapy (up to two years of treatment) with second-line anti-TB drugs which are more costly than first-line drugs, and which produce adverse drug reactions that are more severe, though manageable. Quality assured second-line anti-TB drugs are available at reduced prices for projects approved by the Green Light Committee.
The emergence of extensively drug-resistant (XDR) TB, particularly in settings where many TB patients are also infected with HIV, poses a serious threat to TB control, and confirms the urgent need to strengthen basic TB control and to apply the new WHO guidelines for the programmatic management of drug-resistant TB.
The Stop TB Strategy, the Global Plan to Stop TB, 2006–2015 and targets for TB control
In 2006, WHO launched the new Stop TB Strategy. The core of this strategy is DOTS, the TB control approach launched by WHO in 1995. Since its launch, 41 million patients have been treated under DOTS-based services. The new six-point strategy builds on this success, while recognizing the key challenges of TB/HIV and MDR-TB. It also responds to access, equity and quality constraints, and adopts evidence-based innovations in engaging with private health-care providers, empowering affected people and communities, to help strengthen health systems and promote research.
The six components of the Stop TB Strategy are:
1. Pursue high-quality DOTS expansion and enhancement. Making high-quality services widely available and accessible to all those who need them, including the poorest and most vulnerable, requires DOTS expansion to even the remotest areas.
2. Addressing TB/HIV, MDR-TB and the needs of poor and vulnerable populations. Addressing TB/HIV, MDR-TB and the needs of poor and vulnerable populations requires much greater action and input than DOTS implementation and is essential to achieving the targets set for 2015, including the United Nations Millennium Development Goal relating to TB (Goal 6; Target 8).
3. Contribute to health system strengthening based on primary health care. National TB control programmes must contribute to overall strategies to advance financing, planning, management, information and supply systems and innovative service delivery scale-up.
4. Engage all care providers. TB patients seek care from a wide array of public, private, corporate and voluntary health-care providers. To be able to reach all patients and ensure that they receive high-quality care, all types of health-care providers need to be engaged.
5. Empower people with TB, and communities through partnership.Community TB care projects have shown how people and communities can undertake some essential TB control tasks. These networks can mobilize civil societies and also ensure political support and long-term sustainability for TB control programmes.
6. Enable and promote research. While current tools can control TB, improved practices and elimination will depend on new diagnostics, drugs and vaccines.
The strategy is being implemented as described in The Global Plan to Stop TB, 2010-2015. The Global Plan is a comprehensive assessment of the action and resources needed to implement the Stop TB Strategy and to achieve the following targets:
· Millennium Development Goal (MDG) 6, Target 8: Halt and begin to reverse the incidence of TB by 2015;
· Targets linked to the MDGs and endorsed by the Stop TB Partnership:
o by 2015: reduce TB prevalence and death rates by 50% relative to 1990;
o by 2050: eliminate TB as a public health problem (1 case per million population).
Progress towards targets
The treatment success in the 2008 DOTS campaign was 86% overall, surpassing the 85% target for the first time. The treatment success target was met by 13 of the 22 high-burden countries. However, the regional average cure rates in the African, American and European regions were below 85%.
It is estimated that the global TB incidence rate peaked in 2004. Therefore, the world as a whole is on track to achieve the MDG target of reversing the incidence of TB. Incidence rates are falling in five of WHO’s six regions (the exception is the South-East Asia Region, where the incidence rate is stable). All WHO regions are on track to achieve the 50% mortality and prevalence reduction target, except for the Africa region (although rates of mortality are falling).
