Tuberculosis (TB)

Tuberculosis (TB) is an infection caused by a bacterium called Mycobacterium tuberculosis.  TB usually affects the lungs, but any part of the body can be affected.  Anyone can develop active TB, but one is more likely to develop if in poor health or has a poor immune system. With treatment, most cases are cured. Without treatment, TB may progress or be fatal. A long course of treatment (usually six months), is required and it is important to take the treatment properly in order to cure the TB.

Tuberculosis (TB) infection

Most cases affect the lungs at first. TB germs are coughed or sneezed into the air by people with active TB disease. The bacteria are carried in the air in tiny water droplets. If you breathe in some TB bacteria, they may multiply in your lung. There are then three ways the infection may progress.

  1. Minor infection with no symptoms – occurs in most cases

Most people in good health who breathe in TB bacteria do not develop active TB disease. The TB bacteria that are taken in begin to multiply in the lung. This stimulates the body defences (immune system) into action. The TB bacteria are killed or made inactive by the immune system. There may be some mild symptoms for a short time, or no symptoms, and the infection is halted.

Persons are not usually aware that they have had this mild infection. A small scar on the lung may be seen on a chest X-ray. This may be the only indication of a previous TB infection.

  1. Infection progressing into active TB disease – occurs in some cases

Active TB disease with symptoms occurs in some people who breathe in some TB bacteria. In these people the immune system does not win the battle to halt the invading bacteria. The TB bacteria multiply further and spread to other parts of the lung and body. Symptoms of active TB then develop about 6-8 weeks after first breathing in these bacteria.

TB infection which progresses to active disease can occur in anybody who is infected with TB bacteria. However, it is more likely if you are already in poor health. For example, it is common in malnourished individuals. Newborn babies are also more at risk of active TB.

  1. Secondary (reactivated) infection causing active disease

Some people develop active TB months or years after a minor TB infection had been halted. The body’s immune system at first stops the bacteria from multiplying (as above). However, not all the bacteria may be killed. Some bacteria may be ‘walled off’ in the scar tissue of the initial minor infection. They are stopped from multiplying by the immune system. They do no harm but can remain inactive for many years. The inactive TB bacteria may later start to multiply and cause active TB if the body’s immune system becomes weaker for some reason.

 

 

Symptoms of active tuberculosis (TB)

Cough lasting more than three weeks is often a first symptom. It can start as a dry irritating cough. It tends to continue for months and get worse. In time the cough produces a lot of phlegm (sputum), which may be bloodstained.

Other common symptoms are a high temperature (fever), sweats, feeling unwell, weight loss, pains in the chest, and poor appetite. Breathless may occur if the infection progresses and damages the lungs. If left untreated, complications often develop, such as fluid collecting between the lung and the chest wall (pleural effusion).  If the TB gets close to a blood vessel in the lung then blood may be coughed up.

TB infection sometimes spreads from the lungs to cause infection in other parts of the body. Depending on which part of the body is affected, various symptoms may then occur:

How infectious is tuberculosis (TB)?

A person with active TB disease in the lungs, will cough and sneeze TB germs (bacteria) into the air, which can infect others. To catch TB normally close and prolonged contact with a person who has active TB in the lungs is needed. So, the people most likely to be infected will be those in the same house or same family.

How common is tuberculosis (TB)?

TB is common in developing countries.  It causes more deaths worldwide than any other infectious disease (about three million per year).  Pakistan ranks 5th amongst the high burden countries in the world. The prevalence, incidence and mortality per 100,000 population per year from TB in Pakistan are 348, 276 and 34 respectively (from the national tb program web page).  The main factors contributing to TB in the developing world are:

  • Poor nutrition
  • Poor housing
  • Poor general health
  • Insufficient healthcare
  • AIDS (TB is common in people with AIDS)

Risk factors for tuberculosis (TB)

Anyone can get TB. The risk is increased where one or more of the following apply:

  • Close contacts of a person who has active TB in the lungs (living in the same household, or spending a lot of time with that person).
  • If one lives in a country where TB is common.
  • Environment and poverty: rates of TB are higher among homeless people, prisoners, in large cities and in more deprived areas.
  • A poor immune system: for example, due to HIV infection, immune-suppressing treatment, alcohol or drug addiction.
  • Malnutrition: poor nutrition and lack of vitamin D are linked to TB.
  • Age: babies, young children and the elderly are more susceptible to TB.

Diagnosis of tuberculosis (TB)

Diagnosing TB is sometimes straightforward, but the diagnosis may be more difficult for some people.  In general, the diagnosis is made by looking at the clinical picture (symptoms and a doctor’s examination), combined with the results of certain tests. To start with, a chest X-ray and/or a tuberculin skin test are done followed by phlegm (sputum) tests.

Chest X-ray

A chest X-ray usually shows any active lung TB. It may also show healed or inactive TB.

Tuberculin skin testing (Mantoux test)

This test shows whether a person has been in contact with TB germs (bacteria) at some point during life. The tuberculin is made from part of the TB bacterium. It is injected into the skin. The injection site is examined a few days later.  A positive reaction is a red inflamed area of the skin. This means that you have an active infection, or have had a previous infection, or you have been immunised in the past with BCG. (BCG is the vaccine used to prevent TB.) A negative skin reaction tends to rule out TB.

Sputum tests

If the chest X-ray or tuberculin test results suggest that TB is possible, the next test will be to look for TB bacteria from the lung. This is done by sending samples of sputum to the laboratory.

First, a smear of the sputum is examined in a laboratory, under a microscope using a special dye (stain) to show the TB bacteria. The results are obtained quite quickly, usually within a few days.

Another test for the sputum samples is a culture test. This involves growing (culturing) the TB bacteria in the laboratory. This can take several weeks because TB bacteria grow slowly. There are two important reasons for doing this test. Firstly, to detect TB bacteria that may not be found on the smear test. Secondly, the culture test can check whether the TB bacteria are resistant to any antibiotic medicines.

It can take several weeks for the sputum test results to ‘prove’ the infection. Therefore, many people with suspected active TB (with typical symptoms and X-ray changes) are started on treatment before the results are back. This is to prevent the disease from getting worse, and to prevent spread to other people.

Treatment for tuberculosis (TB)

‘Normal’ antibiotics do not kill TB germs (bacteria). A combination of special antibiotics is needed for several months. Standard treatment is usually for six months. First, it involves a combination of four antibiotics that taken for two months. These are isoniazid, rifampicin, pyrazinamide, and ethambutol. This is followed by continuing with rifampicin and isoniazid for a further four months. The treatment plan may be different, depending on the type of TB and which part of the body is affected.

If treatment fails, it is often due to not taking medication properly and regularly. It is vital that instructions are followed about medication. Even if the patient feels much better in a few weeks (as many people do), the full course of treatment must be completed.

Important of a full course of treatment

The TB bacteria in the body are more difficult to get rid of than ‘ordinary’ bacteria. Only a long course of treatment can fully clear TB bacteria from the body. If the full treatment is not followed then the following problems often occur:

  • The patient remains infectious to other people.
  • The patient may not be cured. Despite feeling better at first, some TB bacteria may stay in the body. These can reactivate at a later time and make the pateint very ill.
  • If the original infection is only partly treated, the bacteria can become resistant to antibiotics (explained below). The TB then becomes more difficult to treat.

Side-effects of tuberculosis (TB) treatment?

The medicines used to treat TB have a good safety record. Sometimes side-effects occur. If one does, see a doctor urgently, so that your treatment can be adjusted or changed to a different antibiotic.

  • Liver problems. blood tests to monitor liver function are required. It is common to get mildly abnormal liver tests when taking TB treatment. This doesn’t always mean that the treatment needs to be changed. Symptoms of liver problems are:
    • A yellow tinge to the skin and eyes (jaundice)
    • A high temperature (fever)
    • Feeling sick (nausea)
    • Itching
    • Feeling generally more unwell.

If any of these occur a doctor should be consulted urgently.

  • Vision changes (if taking ethambutol). Early symptoms are slight loss of vision or loss of colour vision. If any loss of vision occurs, a doctor should be seen urgently. Vision can recover fully if the ethambutol is stopped quickly. A sight test is required before taking ethambutol.
  • Nerve problems (neuropathy) if taking isoniazid. This can cause numbness and tingling in the arms and legs. It can be helped by taking an extra vitamin (pyridoxine) – which is sometimes prescribed together with the isoniazid.
  • Rifampicin makes your tears and urine orange-coloured. This is normal.

 

How do I get tests and treatment for tuberculosis (TB)?

Tests and treatment for TB are free to everyone in the UK – even if you are not a UK resident for everyone in Pakistan under the National TB Control Program.   It is integrated with Primary Health Care (PHC) system implemented by the district health authorities with the support of Provincial TB Control Programs (PTPs)..

Are precautions needed to stop others catching the infection?

A patient with active tuberculosis (TB) in the lung, can infect other people until treatment has been taken for two weeks. After that, normally the TB patient will not be infectious but has to continue with the treatment. During the first two weeks of treatment, it is recommended that the patient stay at home and avoid contact with anyone who has a poor body defences (immune system)

Do family, friends or colleagues need tests?

Household members and close regular contacts of a person with active tuberculosis (TB) may be advised to have tests. Close regular contacts may include colleagues, friends or classmates, depending on the situation and on how infectious the TB is. The usual tests for contacts are a chest X-ray and/or a tuberculin test (Mantoux test). If these show possible TB, then further tests can be done to look for active TB.

Special rules apply for babies and young children under two years who have been in contact with active TB. Diagnosing TB in young children is difficult. In the early stages, the infection may not show up on tests. But young children are vulnerable to TB (they can get a severe infection). Therefore, they may be started on some treatment (such as isoniazid) for several weeks. This helps to prevent a severe infection whilst having further tests to see if TB is present.

Special circumstances

Drug-resistant tuberculosis (TB)

Some people have TB germs (bacteria) which are ‘resistant’ to certain antibiotics – meaning that the bacteria are not killed by that antibiotic. This means that other antibiotics have to be used instead, to cure the TB. So antibiotic resistance can make the TB more difficult to treat, and more dangerous to others who are infected. Difficulty of treatment is increased if the bacteria are resistant to more than one antibiotic. This is called multidrug-resistant (MDR) TB. If the bacteria are resistant to more than three antibiotics, this is called extensively drug-resistant TB.

Drug-resistant TB can be due to not taking a full course of treatment, or to catching TB with bacteria that are already resistant.

Multi drug-resistant TB is extremely dangerous and extra precautions are needed to prevent the infection spreading to others.. Different antibiotics from the standard treatment above are prescribed, with advice from a specialist.

What is the outlook (prognosis) if you have active tuberculosis (TB)?

With treatment, most people make a full recovery. If left untreated, about half of people with active TB eventually die of the infection. TB germs (bacteria) multiply quite slowly compared to most other bacteria. Therefore, active TB tends to cause an illness that slowly gets worse.

How can tuberculosis (TB) be prevented?

TB is both preventable and treatable. It is a tragedy that it remains one of the biggest killers worldwide. Relieving poverty, better nutrition and prompt treatment of TB are the most important ways of reducing TB worldwide. Immunisation (the BCG vaccine) also helps.

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