Worldwide more people die from TB than from any other infectious disease. TB is an abbreviation of the word Tuberculosis and is how people often refer to the disease. TB is caused by bacteria called Mycobacterium tuberculosis (M.tuberculosis).
Bovine TB is a disease caused by similar bacteria called Mycobacterium bovis (M. bovis). Bovine TB mainly affects cattle but can also affect humans. Most of the information on this website refers to the disease in humans.
How do you get TB?
TB is spread from one person to another through the air. You get TB by breathing in TB bacteria that are in the air. Bacteria get released into the air by someone who already has the bacteria in their body.
The bacteria that usually cause the disease in humans, usually affect the lungs, but can affect other parts of the body. If you are infected with the bacteria you won’t necessarily become sick, because you can have either latent TB or TB disease.1“Basic TB Facts”, CDC www.cdc.gov/TB/topic/basics/default.htm People with latent TB do not feel sick and do not have any symptoms.
Undernutrition increases the likelihood of latent TB infection progressing to active TB disease.2JP Cegielski, “The relationship between malnutrition and tuberculosis: evidence from studies in humans and experimental animals”, Int. J. Tuberc. Lung Dis. 2004;8:286-98 TB disease also increases under nutrition. Many people also have concerns about the food that they can eat when they have TB. There is more about food & TB and about TB and nutrition.
TB disease is what happens when a person has latent TB and then becomes sick. Sometimes this is known as having active TB. Overall about 5 to 10% of people with latent TB, who do not receive treatment for it, will become sick at some time in their lives.3“Basic TB Facts”, CDC www.cdc.gov/TB/topic/basics/risk.htm
Some people become sick soon after they have become infected, before their immune system (the part of the body that fights diseases) can fight the bacteria. Other people don’t get sick at first but they get sick years later when their immune system becomes weak for another reason. This can be because they have an infection, such as HIV, or some other health problem.
Some people are known to have a higher risk of becoming ill.4“Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings 2005”, CDC, 5 www.cdc.gov/tb/publications/guidelines/infectioncontrol.htm
- Infants and children aged less than 4 years
- People infected within the previous two years
- People infected with HIV
- People who have certain illnesses or conditions which affect their immune system, such as people with diabetes, and people with chronic renal failure.
What are the symptoms of TB?
The symptoms depend on which area of the body has been infected. If someone has pulmonary disease, which is TB in the lungs, then they may have a bad cough that lasts longer than two weeks. They may also have pain in their chest and they may cough up blood or phlegm from deep inside their lungs. Other symptoms of TB include weakness or fatigue, weight loss, lack of appetite, chills, fever and night sweats.5“Get the Facts About TB Disease”, CDC www.cdc.gov/tb/publications/pamphlets/default.htm
It is very difficult to diagnose TB by a person’s symptoms on their own. This is because some other diseases have the same symptoms.
A diagnosis is usually only certain when there is definite evidence of TB bacteria. Some of the TB tests used for diagnosis look directly for the bacteria. Others such as the chest X-ray look for the effect of the bacteria on the person suspected of having TB. Tests for diagnosis include the TB skin test, sputum microscopy, the culture test as well as the new Genexpert test.
Major problems with the older tests are the lack of accuracy as well as the time they take. With newer tests a major issue is the cost.
TB can usually be cured and more than twenty drugs have been developed for treating TB. But most of the drugs were developed many years ago. The treatment usually consists of a combination of TB drugs that must be taken for at least six months. But the treatment will only be successful if the drugs are taken exactly as required for the entire length of time.
The drugs are used in different combinations in different circumstances. For example, the five “first line” drugs are given to people who have never had treatment before.
Some of the drugs have very severe side effects and are very difficult to take for such a long period of time. This is why there is an urgent need for new TB drugs to be developed. In addition many people are now resistant to one or more of the drugs.
There is also a two way link between TB & nutrition. TB makes under nutrition worse, and under nutrition makes TB worse.
Drug resistant TB
If someone has drug resistant TB it means that the bacteria in their body won’t be affected by certain drugs that they are resistant to. The drugs just won’t work. There are two main reasons why people develop it. It can be because the person doesn’t take their drugs properly. It can also be that the bacteria that they are infected with, have come from someone who has already got drug resistant TB. Being drug sensitive is the opposite of being drug resistant.
If someone has drug resistant TB then they must change drugs. But usually they mustn’t have just one new drug. They need to have several new drugs and for it to be believed that they will all be effective. Drug susceptibility testing which is available in many countries, and is very important, provides information about which drugs a person is resistant to.
A major part of the prevention of TB is to stop the spread of bacteria from one adult to another. This is done by firstly finding the adults who have TB. Then providing them with effective treatment which means that they are no longer infectious, and they will also usually then recover from being sick. There is a vaccine, the BCG vaccine, but it is used for children as it doesn’t seem to prevent the disease in adults.
TB infection control is also important to prevent people from getting infected in health care facilities.
Sometimes it is believed that education only needs to involve people who already have the disease. But there is also a need to educate the general public. This is firstly to ensure that people know how the disease is spread, but also to reduce the stigma surrounding the disease. It can also help to ensure that people with TB come forward for testing and treatment as soon as possible.
The statistics for TB show how there are very different levels of TB in different parts of the world. Not only national governments, but organisations such as the World Health Organisation (WHO) are making significant efforts to End TB.
The countries known as the high burden countries are those with the highest level of disease. They include India, Indonesia, China and Nigeria. Many countries are now making greater efforts to combat TB. In India the government recently announced that its aim is to eradicate the disease by 2025. It has also announced a new strategic plan, the National Strategic Plan 2017 - 2025 setting out how it plans to achieve this. South Africa is another country greatly affected, and this is mainly because of the very high levels of HIV.