Tuberculosis or TB is an infection caused by a bacterium called Mycobacterium tuberculosis. It is spread through the air and usually infects the lungs, although other organs are sometimes involved. Most people infected with this bacterium never develop active TB, but people with weakened immune systems may be prone to be being actively infected. It has become more common recently due to a number of factors, mainly;
• The spread of HIV and AIDS
• Crowded housing conditions with poor sanitation
• Increasing poverty and homelessness
• Intravenous drug abuse
• A poor compliance with the treatment of TB, especially among disadvantaged groups.
What Causes Tuberculosis?
Mycobacterium tuberculosis is an airborne bacterium, the transmission of which usually only occurs after prolonged exposure to someone with active TB. It has been estimated that people have a 50 per cent chance of becoming actively infected if they spend eight hours a day for 6 months or 24 hours a day for two months in contact with someone with active TB. People are most likely to be infectious when their spit contains bacilli - active bacteria - or if they cough a great deal and when the extent of their lung disease is great.
In general, TB of the lung is not infectious two weeks after an infected person has started treatment. Any other types of TB apart from lung TB are not infectious and only people with active lung disease are contagious.
What Are The Signs And Symptoms Of Tuberculosis?
Symptoms of TB are extremely varied, and usually depend upon which part of the body is infected.
Lung TB Can Cause;
• Cough with phlegm, sometimes bloody
• Shortness of breath
• Loss of appetite
• Weight loss
Fever and weight loss are symptoms general to TB, but lymph gland TB will cause an increase in the size of the body's glands. Other areas affected - such as the kidneys, bones, and joints - have symptoms dependant on the extent and severity of the infection but these are relatively rare in the UK compared to lung TB.
The incubation period of active TB is usually 4 to 12 weeks.
Will I Have Any Tests Or Investigations?
The tuberculin skin test (also known as the Mantoux test) can identify most people infected with tubercle bacilli six to eight weeks after initial exposure. A purified protein derivative (PPD) is superficially injected under the skin of the forearm, and examined 48 to 72 hours later. If there is a reddening reaction around this site, there may have been exposure to the TB organism but it does not mean active infection is present. Most people with previous exposure to TB will test positive on this test, as will some people exposed to related mycobacteria.
This test then leads on to further tests such as a chest X-ray and sputum sample collection for analysis - this can take up to 4 weeks to confirm because the bacterium grows very slowly. The chest X-ray will usually show cavities or lesions in the lungs, but the final diagnosis remains a combination of these X-rays, clinical findings and a previous history of exposure to TB.
What Treatment Will I Need?
Most people are readily cured by a course of antibiotics, but usually three or four antibiotics are required to be taken together for a course of at least 6 months. Treatment usually comprises the drugs isoniazid and rifampicin, and pyrazinamide, which is given in the early stages of treatment. Occasionally a drug called ethambutol is added if your doctor suspects that drug resistance may be a problem. It is vital that anyone on such treatment finishes their course of treatment to both achieve a cure and reduce the rise of multi-drug-resistant TB - this often now needs a second line of TB drugs, often for up to 2 years of treatment.
What Course Will The Illness Follow?
Over 90 per cent of people with active TB, and in the absence of HIV or AIDS, achieve a permanent cure after correct treatment. If TB is left untreated however, it remains a serious cause of mortality with a death rate of between 40 and 60 per cent. It is much more common in other parts of the world such as Africa and the Indian subcontinent than in the UK. People with lung TB can return to work once they have taken two weeks of treatment - people with other types of TB can return once they feel well enough.
People who have been in close contact with a person diagnosed as having TB will be contacted by a TB health visitor, tested, and may require antibiotic treatment.
Can I Do Anything To Help Myself?
TB is, by and large, a preventable disease. Prevention tends to focus on those people who run the highest risk of developing active disease, but once diagnosed the main factor in becoming cured is the correct use and duration of any treatment that is prescribed.
Tell Your Doctor
1. Are you aware of having any recent contact with someone who has TB?
2. Are you coughing up spit or blood?
3. Are you at any risk from HIV?
4. Are you short of breath easily?
5. Do you have a fever?
Ask Your Doctor
1. What is the vaccination programme against TB in the UK?
2. Can my young children be treated if I have TB?
3. How long will I need follow up treatment or checks for?
4. Am I routinely tested for HIV if I have TB?
5. Will I have to attend a TB clinic?
British Lung Foundation
Address: 78 Hatton Garden, London, EC1N 8LD
Telephone: 0207 831 5831
Fax: 0207 831 5832
Website URL: www.blf.org.uk
Address: PO Box 935, Harrow, Middlesex, HA1 3YJ
Telephone: 0208 423 8999
Helpline: 0845 608 4455
Website URL: www.patients-association.com
British Thoracic Society
Address: The British Thoracic Society, 17 Doughty Street, London WC1N 2PL
Telephone: 0207 831 8778
Fax: 0207 831 8766
Website URL: www.brit-thoracic.org.uk
Website URL: www.aidsmap.com
By Dr Roger Henderson, MB BS Lond., LMSSA Lond.