Published On:Monday, March 15, 2010

PART ONE

(EDITOR'S NOTES: The Bahamas will join the rest of the world in the observance of World Tuberculosis day on March 24, 2010. More than a decade after it was identified as a global health emergency, tuberculosis remains one of the world's leading infectious causes of death among adults. About one-third of the world's population carry the TB bacteria, although most never develop active TB disease. TB disease has been on the rise since the 1980s.)

What is tuberculosis (TB)?

Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of the body, but they usually attack the lungs.

How is TB spread?

TB is spread through the air from one person to another. When an infectious person coughs, sneezes, talks, or spits, they can release TB germs, into the air. People nearby might breathe in these bacteria and become infected.

When a person breathes in TB bacteria, the bacteria can settle in the lungs and begin to multiply. From there, they can move through the blood to other parts of the body, like the kidney, spine, and brain.

TB in the lungs (referred to as pulmonary TB) and/or the throat can be infectious. This means that the bacteria can be spread to other people. TB in other parts of the body (referred to as extra pulmonary TB) usually is not infectious.

According to the World Health Organization (WHO), if left untreated, a person who has pulmonary TB and has symptoms of the disease will infect, on average, between 10 to 15 people every year.

How does TB disease develop?

There are two possible ways a person can develop TB disease. The first applies to a person with latent TB infection or exposure, a condition which occurs when a person might have been infected with TB for some time but has otherwise been healthy, without symptoms, and is not infectious. However, it is possible for latent TB infection or exposure to become active at any time, particularly if a person's immune system is weakened. In this way, a person might become sick with TB disease months or even years after they first breathed the TB bacteria.

The other way TB disease develops happens much more quickly. Sometimes when a person first breathes in the TB bacteria, the body is unable to protect itself against the disease. The bacteria then develop into active TB disease within weeks.

What is latent TB infection or Exposure?

Most people who become infected with TB are able to fight the bacteria and stop them from multiplying. In many of these people, the bacteria become dormant. This is called latent TB infection. A person with latent TB infection or exposure usually has a positive skin test reaction, but has no symptoms and cannot spread TB to others.

TB bacteria remain alive in the body of those who have latent TB and can become active at a later point in time. The World Health Organization (WHO) estimates that approximately 5 per cent to 10 per cent of individuals infected with the TB bacteria actually become sick with the disease during their lifetime. For persons whose immune systems are weak, particularly those with HIV, the risk of developing active TB disease is considerably higher than for persons with normal immune systems. This is because in people who have weakened immune systems, the dormant TB bacteria can reactivate, thereby changing the person's status from latent infection or exposure to active disease.

What is active TB disease?

TB bacteria become active if the immune system cannot stop them from multiplying and the bacteria can cause active TB disease. People with active TB disease can spread the disease to others. Those with active TB will often exhibit symptoms such as heavy coughing, fatigue, chills, and fever. Some people develop TB disease soon after becoming infected with the TB bacteria, before their immune system can fight and kill it. Other people might get sick later, when their immune systems become weak for some reason. Most people infected with TB do not develop active TB disease and instead have what is called latent TB.

Is isolation required for persons with TB?

Isolation is the separation and confinement of infected individuals, in hospital where the individual receives intensive therapy for fourteen days. In most hospitals, it is common practice for patients who have active TB and are infectious to be isolated. This is done to prevent the spread of the disease. On the other hand, patients who have latent TB infection do not require isolation. When the person is discharged from hospital, he or she is not considered infectious and therefore, can no longer expose other people to TB.

* For more information of TB screening, prevention and control, see parts two and three of this series. You may also contact the TB Surveillance Unit of the Department of Public Health at telephone numbers 502-4708 or 502-4803. Tune in to Joining Hands for Health Radio Programme each Wednesday evening at 7.30pm, on Radio Bahamas ZNS 1540 AM where topics relevant to maintaining good health are discussed.