Tuberculosis (TB)

Active TB is a serious condition that usually affects the lungs. Anyone can develop active TB, but you are more susceptible to the condition if you are in poor health or have a weak immune system. With treatment, most cases are cured. Without treatment, TB can be fatal. Treatment needs to be taken for at least six months.

What is tuberculosis?

Tuberculosis (TB) is an infection caused by a germ called mycobacterium tuberculosis. TB usually affects the lungs but any other part of the body may also be affected.

What is atypical tuberculosis?

Another bacterium called mycobacterium bovis, rarely also causes TB. It is passed on from contaminated unpasteurised milk, or from infected cattle.

There are various other bacteria in the mycobacterium family which are called atypical mycobacterium. Most of these do not cause infection.

How does TB occur?

In most cases the lungs are affected first. TB bacteria is coughed or sneezed into the air by people with active TB. If you inhale TB bacteria, it may then multiply in your lungs. There are three ways the infection may progress:

1. Minor, short-lived infection with no symptoms

Most people in good health who inhale TB bacteria do not develop active TB. The bacteria that you inhale are attacked and made inactive by your immune system. There may be some mild symptoms for a short period, or no symptoms at all, and the infection is halted. This is the end of the matter for most infected people.

2.  Infection progressing into active TB

Active TB with symptoms occurs in about one out of 20 people who inhale some TB bacteria. In these people the immune system does not stop the invading bacteria. Symptoms of active TB then develop in different parts of the body, about four to eight weeks after first inhaling the bacteria. This course of events is more likely if you are in poor health, for example, it is common in malnourished children.

3.  Re-activated (secondary) 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. Some bacteria may however become embedded in the scar tissue of the initial minor infection. They do no harm but can remain inactive for many years. These TB bacteria may eventually start to multiply and cause active TB if the body's immune system begins to fail later in life. A failing immune system and re-activated TB is more likely to occur if you are:

• elderly or frail;
• malnourished;
• HIV positive;
• diabetic;
• taking steroids or immunosuppressant medication;
• suffering from kidney failure; or
• alcohol dependent (alcoholic).

Symptoms of active TB

Coughing is usually the first and most distinct symptom. The cough often starts as a dry irritating cough. It tends to continue for months and worsens over time. The cough usually becomes phlegm-producing, which may be bloodstained.

Other symptoms include:

• fever;
• sweats;
• feeling unwell;
• weight loss;
• chest pains; and
• loss of appetite.

If left untreated, complications often develop such as fluid collecting between the lung and the chest wall, which can cause breathlessness. The infection may spread in the bloodstream and lymphatic system causing swollen lymph glands, and infection in other parts of the body. Various other symptoms may then occur.

How infectious is TB?

If you have been infected with TB but have none of the symptoms mentioned above, you cannot pass on the infection. If you have active TB of the lungs you will cough TB bacteria into the air which may infect others.

How common is tuberculosis?

TB is very common in South Africa and causes many deaths. Poor nutrition, sanitation and living conditions, general health and the AIDS epidemic are some of the main reasons why TB is widespread in South Africa.

Diagnosis of TB

Typical symptoms and changes on the chest X-rays suggest active TB. These changes are not always present and further tests are usually done to prove the diagnosis.

Tuberculin skin testing (mantoux, heaf or tine test)

This is a useful test which shows if you have been in contact with TB bacteria at some point in your life. However, it cannot prove you have a current active infection. Tuberculin is a part of the TB bacterium. It is injected into the skin; and the area is examined a few days later.

A negative skin reaction tends to rule out TB. A negative test means you have never been infected with TB and have not had a BCG immunisation (preventative vaccine). On rare occasions, a negative result occurs if you have severe active TB.

A positive reaction is a red inflamed area of the skin. This means that you either have a current infection, or have had a previous infection, or you have had a BCG immunisation in the past.

Proving a current active infection

A sample of one's phlegm (sputum) is usually taken, in an attempt to grow TB bacteria to prove that you currently have active TB. However, it often takes six to eight weeks to get a result from this test as the TB bacteria grows and multiplies very slowly before they can be detected in the laboratory. Newer tests are being developed which may speed up the process of diagnosis of TB.

It may take several weeks for the results to 'prove' that the infection is present, therefore many people with suspected active TB (with typical symptoms and x-ray changes) are started on treatment before the sputum results are ready. This is to prevent the condition from worsening, and to prevent it from spreading to other people.

Treatment of TB

A combination of special antibiotics is prescribed over a period of six months. Standard treatment in South Africa is usually a combination of three or four antibiotics that is taken over a period of two months. Variations on this treatment plan may be advised depending on individual circumstances.

The most common reason for treatment failure is due to patients not taking their medication correctly and regularly. It is vital that you follow the instructions as directed by your doctor. Even if you feel much better in a few weeks (as many people do) you must finish the full course of treatment.

The medication used to treat TB has a good safety record. Side-effects have been known to occur in some patients. If you experience any side-effects, see a doctor rather than just stopping treatment. An alternative antibiotic may be an option in such a case.

Testing of family, friends and close contacts

Household members and close regular contacts of the patient with active TB may be advised to have tests done to ensure safety. This may include a tuberculin skin test and a chest x-ray.

Outlook for patients with active TB

With treatment, most people make a full recovery. If left untreated, about half of people with active TB eventually die. Drug resistant TB may develop if medication is not taken as prescribed by your doctor.

Prevention of TB

TB is both preventable and treatable. It is a tragedy that the epidemic remains one of the biggest killers in South Africa. The most important ways of preventing TB include:

• regular medication for sufferers;
• relieving poverty;
• improved nutrition, general health and living conditions; and
• the BCG vaccine. 

Immunisation against TB

The BCG vaccine is offered to:

• babies at birth;
• people at risk due to their job, for example, health workers, prison staff, etc.;
• close contacts of patients with active TB; and
• people who intend to stay for one month or more in countries with a high TB rate.

The BCG vaccine is thought to give more than 70% protection against TB. So, although it is a good vaccine, it does not guarantee complete protection against TB. Some people still develop TB even though they have had the BCG vaccine.

References

UK Patient information at UK Patient and South African TB Guideline 2000