What is TB?
Tuberculosis (TB) is a contagious disease that kills approximately 2 million people each year. One-third of the world's population is currently infected with TB and someone is newly infected every second.
What is the relationship between TB and HIV?
TB is the leading cause of death among HIV infected people; it has been estimated that the disease accounts for 13% of AIDS deaths worldwide. When someone is infected with TB, the likelihood of them becoming sick with the disease is increased many times if they are also HIV-positive.
What causes TB?
TB is caused by the bacteria Mycobacterium tuberculosis. The bacteria can attack any part of the body, but it normally attacks the lungs. TB is highly prevalent in many resource-poor countries and in poor urban 'pockets' of industrialised countries.
The spread of TB
A TB patient covers her mouth in an attempt to stop the spread of disease
A person can have active or inactive TB. The TB bacteria can be spread through the air by people with active TB. People with active TB can pass the bacteria on to whoever they come into close contact with. Active TB or TB disease means that the bacteria is active in the body and the immune system is unable to stop the bacteria from growing. When a person with active TB coughs, sneezes or spits, people nearby may breathe in the TB bacteria and become infected. Left untreated, each person with active TB will infect on average between 10 and 15 people every year.
People can also be infected with TB which is non-active in the body. Inactive TB infection is also called latent TB. If a person has inactive TB, it means that the body is able to fight off the bacteria and is also stopping the bacteria from growing. People who have inactive TB do not feel sick, do not have symptoms and cannot spread TB. In some people TB bacteria remain inactive for a lifetime without becoming active. But in some other people the inactive TB may become active TB if their immune system becomes weakened for example by HIV. People with inactive TB are also called TB carriers.
TB and HIV-positive people
Because TB can spread through the air, the increase in active TB among people infected with both TB and HIV results in:
- more transmission of the TB bacteria
- more people with latent TB
- more TB disease in the whole population
People with latent TB are increasingly becoming infected with HIV, many more are developing active TB because HIV is weakening their immune system. People who are co-infected with both HIV and latent TB have an up to 800 times greater risk of developing active TB disease and becoming infectious compared to people not infected with HIV.1
People with advanced HIV infection are vulnerable to infections or malignancies that are called 'opportunistic infections' because they take advantage of the opportunity offered by a weakened immune system. TB is an HIV related opportunistic infection. A person that has both HIV and active TB has an AIDS-defining illness.
Avert.org has pages about HIV related opportunistic infections in resource poor settings and in well-resourced settings.
As a consequence, the HIV/AIDS epidemic is reviving an old problem in well resourced countries and exacerbating an existing one in resource poor countries.
Also
- TB is harder to diagnose in HIV-positive people
- TB progresses faster in HIV-infected people
- TB in HIV-positive people is more likely to be fatal if undiagnosed or left untreated
- TB occurs earlier in the course of HIV infection than other opportunistic infections
- TB is the only major AIDS-related opportunistic infection that poses a risk to HIV-negative people
What are symptoms of TB?
Nurse checks the progress of TB patient, who has lost much of his body weight
Symptoms of TB depend on where in the body the TB bacteria are growing. TB bacteria usually grow in the lungs. TB in the lungs may cause bad cough that last longer than 2 weeks, pain in the chest, coughing up of blood or sputum. Other symptoms of TB disease are: weakness or fatigue, weight loss, no appetite, chills, fever and sweating at night.
Inactive TB has no symptoms.
How is TB diagnosed?
TB can be diagnosed by injecting a protein found in TB bacteria into the skin of an arm. If the skin reacts with swelling, you are probably infected with TB. Sometimes x-ray is used to diagnose TB. If these facilities are not available then the TB diagnosis is often based on symptoms.
How is TB treated?
As part of the DOTS strategy, TB patient takes daily doses of pills during supervised treatment
TB disease can almost always be cured. TB is usually treated with a combination of antibiotics. The variety of treatments and drug options depend on the country you are in. A proper combination of anti-TB drugs provides both prevention and cure. Effective treatment quickly makes the person with TB non-contagious and therefore prevents further spread of TB. Achieving a cure takes about six months of daily treatment with a combination of antibiotics.
To treat active TB disease, several drugs are needed because there are many bacteria to be killed. Taking several drugs will do a better job of killing all of the bacteria and prevent them from becoming resistant to the drugs To ensure thorough treatment, it is important the person takes his or her pills in the presence of someone who can supervise the therapy. This approach is called DOTS (directly observed treatment, short course). DOTS cures the treatment in 95% of cases. A six-month supply of DOTS costs as little as US$ 10-20 per person in some parts of the world. Also, a drug called isoniazid (INH) can be used as a preventative therapy for those who are at risk of getting infected with TB or with those who have inactive TB. People who have inactive TB but are not yet sick can take the INH drug, so that they will never develop active TB.
TB treatment and HIV
It is important for people with HIV to have treatment when they have active TB. They can be cured of their active TB as well as avoiding transmission to others. Treating TB can improve the quality of life of HIV-positive people and it may prolong their life. Even in settings where antiretroviral drugs are unavailable or inaccessible, it is vital that the health system is able to offer HIV-infected individuals the simple antibiotics needed for DOTS.
For some people it can be difficult to take drugs for both TB and HIV at the same time. Some anti-HIV drugs can also interact with some TB drugs making the treatment more difficult. It is also important that the TB treatment is taken regularly and exactly as the health care provider has advised. If the drugs are not taken regularly, the bacteria can become resistant to the drugs and this can be dangerous.
As one of the first opportunistic infections to appear in HIV-infected people, TB may be one of the earlier signs of HIV infection. Addressing TB offers the opportunity for early HIV intervention.
Although, treatment of TB can improve the quality of life of HIV-positive people and prolong their life, it cannot stop people from dying of AIDS.
What is multi-drug resistant TB (MDR-TB)?
Multi drug resistant TB is a type of TB that is resistant to some antibiotics. When the TB bacteria becomes resistant to more than one drug it is called multi-drug resistant TB or MDR-TB. When TB-patients do not take their medicine as prescribed, the TB can become resistant to certain antibiotic drugs and the drugs then no longer kill the bacteria. MDR-TB is a serious problem and very difficult to treat. The treatment of MDR-TB is also much more expensive that DOTS and takes much longer. Being HIV-positive does not itself increase the change of drug resistance.
TB around the world
The importance of TB to the global HIV epidemic is enormous. TB is also a serious health problem in its own right but TB is also the most likely cause of death for HIV-positive people. Like HIV, TB has had an uneven impact around the world. In some parts of the world, TB is increasing after almost 40 years of decline. Escalating TB rates over the past decade in many countries in sub-Saharan Africa and in parts of south East Asia are mainly attributable to the HIV epidemic.
The largest number of cases occurs in the South-East Asia Region, which in 2002 accounted for nearly 3 million cases per year (a third of the global total). However, the estimated incidence per capita in sub-Saharan Africa is nearly twice that of the South-East Asia, at 350 cases per 100,000 population. Also, the countries of Eastern Europe are facing a growing epidemic; there were 144,000 cases in Russia alone in 2002.
TB is not only a problem in resource poor countries. For example, there were 15,055 cases reported in the U.S. in 2002. TB in the UK is a disease that has never gone away, with 6,889 new cases reported in 2002. Although the UK's national rate is very low in comparison with most of the world, London has become one of the world's TB hotspots. In parts of London, TB rates are ten times the national rate - higher than in some countries of the former Soviet Union. About 10 per cent of London’s TB cases are likely to be co-infected with HIV.2
Worldwide TB control
The discovery of antibiotic drugs, which kill bacteria, was a turning point in TB control. In well resourced countries, TB was previously 'treated with a special diet and bed rest' usually in sanatorium. In the late 1950s, it was found that this was unnecessary and TB could be cured with well-supervised antibiotic treatment at home.
Since DOTS was introduced on a global scale in 1991, more than 13 million people have received DOTS treatment. By the end of 2002, all 22 of the countries with the highest number of TB cases, which together have 80% of the world's estimated incident cases, had adopted the DOTS strategy. In total, 180 countries were implementing the DOTS strategy, and 69% of the global population was living in parts of countries where the DOTS strategy was in place. In India alone, 740 million people (almost 70% of the total population) were living in parts of the country where the strategy had been implemented by August 2003.
The emergence of multi-drug resistant TB threatens TB control efforts across the world, including in well resourced countries. In recent years, drug-resistant TB, including multidrug-resistant TB, was found in all regions of the world. The prevalence of MDR-TB was exceptionally high in almost all former Soviet Union countries surveyed, with drug resistance in new patients as high as 14%. High prevalences of MDR-TB were also found among new cases in China, Ecuador and Israel. Central Europe and Africa, in contrast, reported the lowest median levels of drug resistance.
WHO's leading infectious disease experts estimate there are 300,000 new cases per year of MDR-TB worldwide. There is also new evidence proving drug resistant strains are becoming more resistant, and unresponsive to current treatments. 79% of MDR-TB cases are now "super strains", resistant to at least three of the four main drugs used to cure TB.
Estimated incidence of TB: high burden countries, 2002
| Country | Population | All cases |
| India | 1,049,549,000 | 1,761,000 |
| China | 1,294,867,000 | 1,459,000 |
| Indonesia | 217,131,000 | 557,000 |
| Nigeria | 120,911,000 | 368,000 |
| Bangladesh | 143,809,000 | 318,000 |
| Pakistan | 149,911,000 | 272,000 |
| Ethiopia | 68,961,000 | 255,000 |
| Philippines | 78,580,000 | 251,000 |
| South Africa | 44,759,000 | 250,000 |
| DR Congo | 51,201,000 | 196,000 |
| Russian Federation | 144,082,000 | 182,000 |
| Kenya | 31,540,000 | 170,000 |
| Viet Nam | 80,278,000 | 155,000 |
| UR Tanzania | 36,276,000 | 132,000 |
| Brazil | 176,257,000 | 110,000 |
| Uganda | 25,004,000 | 94,000 |
| Zimbabwe | 12,835,000 | 88,000 |
| Mozambique | 18,537,000 | 81,000 |
| Thailand | 62,193,000 | 80,000 |
| Afghanistan | 22,930,000 | 76,000 |
| Cambodia | 13,810,000 | 76,000 |
| Myanmar | 48,852,000 | 75,000 |
| Global total | 6,219,011,000 | 8,797,000 |
Page amended by Rob Noble, September 2004.
References
- 1 TB and HIV Coinfection, CDC NCHSTP Division of Tuberculosis Elimination.
- 2 Health Protection Agency - Annual Report and Accounts 2004.
Sources
- World Health Organization. Global Tuberculosis Control: Surveillance, Planning, Financing, WHO Report 2004. Geneva, Switzerland.
- Fact Sheet No 104, World Health Organization, March 2004; accessed 24th September 2004.
- Anti-Tuberculosis Drug Resistance In The World Third Global Report, The WHO/IUATLD Global Project on Anti-Tuberculosis Drug Resistance Surveillance 1999-2002.
Last updated December 2, 2004
