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03 December 2008

TB: Anyone can get it

Tuberculosis does not discriminate. Although the disease is linked to crowded living conditions and lower socio-economic status, any individual is potentially at risk.

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The tuberculosis epidemic is poorly controlled in South Africa, with local disease rates up to 60 times higher here than in the USA and Western Europe. Recently the World Health Organisation expressed concern about this high TB prevalence.

The disease kills approximately 1 000 South Africans every month and the vast majority of TB sufferers are in their most economically productive years, according to the Medical Research Council (MRC).

TB spreads to those in close contact with an infected person, in particular to members of the same household.

The disease is caused by the organism Mycobacterium tuberculosis, which is easily spread when people with active lung disease expel the small airborne TB particles from their lungs into the air through coughing. Other people then breathe in the infectious droplets into their lungs, where the bacteria begin to multiply.

Although it is relatively easy to catch the TB bacteria, in most people the lung infection is short-lived because the immune system is able to contain it. The bacteria can remain dormant for years; although the immune system has contained the infection, it has not eliminated it. In about 5-10 percent of cases the bacteria become active again, causing pneumonia and sometimes spreading elsewhere in the body to cause secondary TB.

TB on the increase
Globally, TB rates have escalated in recent years, especially in developing countries. There has also been an alarming increase in cases in developed countries as of the mid-80s.

This rapid increase is attributed to several factors, including the increasing number of HIV/Aids patients (TB is an opportunistic infection of Aids), the emergence of new drug-resistant TB strains (also in South Africa), and increasing poverty. The huge increase in global trade and air travel since 1960, make it easier for the TB organism to spread to all parts of the world.

Many misconceptions remain. The most important of these are that only HIV-infected individuals can get TB, and that it only affects the poor.

The five most important risk factors
The most important factors that determine the risk to develop TB, are 1) the degree of exposure to adults with active TB, 2) immune-compromising conditions like HIV/Aids, 3) malnutrition, including micro-nutrient deficiencies, 4) chronic lung damage as a result from smoking and 5) genetic susceptibility.

These five main factors can be applied to any individual irrespective of his/her socio-economic status, but it also illustrates why poor communities are particularly vulnerable, says Dr Ben Marais, paediatrician and TB expert at the University of Stellenbosch’s health sciences faculty.

1) The degree of exposure to adults with active TB
In SA we are all exposed to TB to a greater or lesser degree. Health workers and other people, who are frequently exposed to TB patients, should apply extra caution.

2) Immune-compromising conditions
A weakened immune system remains the most important factor in the development of TB after exposure to the organism. Conditions that weaken the immune system include diabetes, cancer, severe kidney disease and immuno-suppressive drugs, corticosteroid treatment or cancer chemotherapy. HIV/Aids is of particular importance because it affects so many people.

Stress may also be a contributing factor. Even though research hasn't directly linked TB to stress, it is clear that excessive stress weakens the immune system and generally increases one's risk of contracting disease, says Marais.

3) Malnutrition and micro-nutrient deficiency
Malnutrition impairs immune function at many different levels.

Not only too little food, but also too little of the right food (fresh fruit and vegetables), compromises the function of the immune system. Certain medical conditions (such as Crohn’s disease, ulcerative colitis, celiac disease or other conditions) may cause inadequate absorption or metabolism of nutrients with resultant malnutrition and vitamin or mineral deficiencies.

Excessive alcohol intake is a particular concern, because it is often associated with poor diet in addition to its independent effects. Impaired digestion and absorption due to liver or pancreatic damage, also play a role in heavy drinkers.

4) Smoking and chronic lung damage
There is a clear association between smoking and reduced local immunity within the lungs.

In smokers, the mucous membranes of the lungs are damaged and inflamed, and the hair cells paralysed. This effect of smoking leaves the lungs vulnerable to infection, including TB. In addition to the fact that the TB bacteria are not efficiently removed after inhalation, chronic lung damage impairs the lung immunity and may increase susceptibility to TB. This is clearly illustrated by the association between silicosis and TB in mine workers, says Marais.

But smoking has an extra sting in its tail. “Several studies have confirmed that smokers have a worse prognosis if they do get TB,” he says.

5) Genetic susceptibility
University of Stellenbosch researchers have recently linked a gene that influences interferon-gamma function to the vulnerability to develop TB. This study was published in The Lancet in 2003.

Although none of us can change the genes that we were born with, it illustrates that all of us should do our utmost to influence the things that are within our reach, e.g. to adopt a healthy diet and lifestyle.

How to reduce your chances of getting TB
You can take definite steps to reduce your risk to develop tuberculosis, says Marais.

Take note of the following:
- Immunisation remains the mainstay of prevention. All babies and children should receive the full course of immunisation.

- Try to limit contact with individuals who have active disease and who are not on treatment. People with disease must comply with their treatment, because within one week of appropriate treatment that individual does not pose a threat to anyone anymore. Don’t be afraid of people with TB, but encourage them to take all their medicine.

- If you or members of your household come into contact with someone who has TB, do not panic. If a domestic worker has TB, ensure that she/he is treated properly, that children younger than five years who have been in contact with the diseased individual receives a skin test to detect possible infection, and that all other contacts are monitored for suggestive symptoms.

- TB is curable, but you can reduce your changes of ever developing TB dramatically by adopting a healthy lifestyle. Stop smoking, cut excessive alcohol intake, manage your stress, exercise daily and follow a well-balanced diet to keep your immune system in optimal shape. This will reduce the threat of the TB bacterium considerably and improve your general health and well-being.

How infectious is someone with TB?
- If you contract TB, it is important that you should be diagnosed and treated as soon as possible. Within one week of starting treatment, you will no longer be contagious. The routine TB treatment available in South Africa is of high quality and effective in the vast majority of cases. All TB patients must complete the full six-month treatment period to prevent disease relapse.

- Infected children do not pose a risk to anyone. The way in which the disease manifests in children differs from adults, making them far less contagious. Although diseased children do not pose a risk, they are at high risk to contract the disease from infectious adult cases.

- (Carine van Rooyen, Health24)

Read more:
Fats could help body fight TB
'Super' TB provides clue to disease

Visit the SA Thoracic Society for more information.

 

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