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Sunday December 22, 2013 MYT 12:00:00 AM
Sunday December 22, 2013 MYT 8:24:38 AM
by dr milton lum
Chest X-rays are a common imaging technique used to identify tuberculosis infection. – Photo AFP
Tuberculosis remains one of the top infectious disease killers in the world.
TUBERCULOSIS (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis, which can only survive in humans, as it is not found in other animals, soil or other non-living things.
TB typically affects the lungs as M. tuberculosis needs oxygen to survive. That is why the M. tuberculosis complexes are always found in the air sacs of the upper lung.
However, TB can affect any part of the body, like the lymph nodes, bones, kidney, brain, spine, reproductive organs, and even the skin.
TB is the second biggest infectious disease killer globally.
Its incidence in Malaysia rose from 64.7 per 100,000 population in 2000 to 71.35 per 100,000 population in 2011. The number of reported TB cases increased from 15,875 in 2005 to 20,666 in 2011.
An estimated one-third of the world’s population are infected with TB bacteria.
About one in 10 of these develop active disease, i.e. they have symptoms, get sick and spread TB to others.
However, the vast majority have latent TB, i.e. they test positive for the disease and their chest X-rays may show evidence of TB, but they have no symptoms, do not get sick or spread TB to others.
The active disease
Active TB develops when two events occur.
Firstly, the bacteria enters the body through the breathing of contaminated air containing microscopic droplets from a TB sufferer when he or she coughs, sneezes, speaks, sings or laughs.
Only people with active TB can spread the disease to others.
Secondly, the body’s immune system cannot control the growth and spread of the disease after the initial infection.
Active TB is more likely to occur in people with poor immunity, e.g. drug users, children below the age of five years, senior citizens, diabetics, the malnourished, HIV/AIDS sufferers and chemotherapy recipients.
More than 20% of TB cases worldwide are attributable to smoking. Overcrowding and social deprivation are also risk factors.
The risk is also increased in people who have not had adequate treatment for TB in the past.
M. tuberculosis grows in the lungs and can spread to other parts of the body within days, weeks, months or years after the initial infection, depending on the level of immunity.
TB affects all age groups, with more young adults being affected.
People who have HIV are 21 to 34 times more likely to become sick with TB.
The spread of TB requires close contact with someone who has the active disease.
The World Health Organisation estimates that people with active TB can infect up to 10-15 other people through close contact over the course of a year.
The symptoms of active TB include fever, night sweats, unexplained weight loss, tiredness and poor appetite.
The symptoms of TB of the lungs include chronic cough (more than three weeks), chest pain and bloody sputum. As some symptoms are vague, they can go unnoticed.
The symptoms of TB affecting other organs varies, depending upon the organ affected. For example, bone pain, if the bones are affected, or subfertility, if the fallopian tubes are infected.
Certain signs in a person’s medical history and physical examination will raise the doctor’s suspicions of TB.
The doctor may then order a Mantoux test.
This involves injecting tuberculin under the skin of the forearm.
A red swelling forming around the injection site within 72 hours is positive, i.e. it means the person has been exposed to M. tuberculosis or bacteria related to M. tuberculosis, or has been vaccinated with the TB vaccine. It does not mean that there is active disease.
Imaging techniques, e.g. X-rays, may show evidence of TB infection.
Sputum and other samples are taken to test for M. tuberculosis by trying to grow the bacteria from those samples in the laboratory.
However, as M. tuberculosis grows slowly, it can take about four weeks to confirm the diagnosis, and an additional two to three weeks to determine which antibiotics to use in treatment.
Other tests may be necessary, especially for TB in organs other than the lungs.
TB is curable in most sufferers with the appropriate antibiotics.
Successful treatment requires close cooperation between patients, doctors and nurses.
The treatment usually involves taking several antibiotics for at least six months, and sometimes, longer.
Drug resistance is on the rise and requires the use of special antibiotics – all of which have potentially serious side effects.
Strict compliance to the treatment regime as instructed by the doctor, will go a long way in controlling this threat.
As TB is an airborne infection, its spread can be prevented with adequate ventilation and limited contact with those having the active disease.
Effective preventive measures include early diagnosis and treatment, maintaining a healthy immune system, and addressing the health needs of those at increased risk.
This could involve preventive antibiotics.
The Bacille Calmette-Guerin (BCG) vaccine is fairly effective in protecting children against the severe complications of TB.
Dr Milton Lum is a member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organization the writer is associated with. For more information, e-mail email@example.com. The information provided is for educational purposes only and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
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Health, Health, Tuberculosis, TB, infectious diseases
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