TB: Common yet fatally infectious

By

Dr Hjh Salizawati bt Mohd Zainal,

Senior Medical Officer,

National Tuberculosis Coordinating Centre, Kiarong

A boy pouring water as villagers collect their own from a lake in the village of Thamada, Myanmar. In 2006, there were 9.2 million new cases of symptomatic tuberculosis and three million deaths from the disease. AFP

Introduction
Tuberculosis or TB (short for tubercle bacillus) is a common yet dangerous infectious disease caused by airborne mycobacterium tuberculosis.

The disease has been a serious public health problem and in the early 19th century, the disease caused more than 30 per cent of all deaths in Europe.

With the advent of anti-tuberculosis drugs in the late 1940s, the battle against tuberculosis seemed to be won.

Unfortunately, in the 1990s, the world faced another threat against tuberculosis with the emergence of drug resistance tuberculosis, the escalation of HIV/AIDs rates, extreme poverty in many parts of the world and hence tuberculosis continues to be a deadly disease worldwide.

In 2006, there were 9.2 million new cases of symptomatic tuberculosis and three million deaths from the disease. And of the 9.2 million new cases, about three million occurred in Africa, three million in Southeast Asia, and about two million in Western Pacific region.
India and China reported the largest total number of new cases, but South Africa had the highest rate of new cases in the world, with 940 new cases per 100,000 people.

In Brunei Darussalam, it was reported in 2008 that there were 223 cases of TB where majority are pulmonary TB.

How Infection Develops
People can be infected with tuberculosis only from a person who has active disease.
The bacteria are spread almost exclusively through the air.

People with active tuberculosis in their lungs often contaminate the air with bacteria when they cough, sneeze, or even speak.

These bacteria can stay in the air for several hours. If another person breathes them in, that person may become infected. Thus, people who have contact with a person who has active tuberculosis (such as family members or health care practitioners who treat such a person) are at increased risk of getting the infection.

In most cases, tuberculosis bacteria that enter the lungs are immediately killed by the body's defences.

Those that survive are engulfed by white blood cells. The engulfed bacteria can remain alive inside these cells in a dormant state for many years (this stage is called latent infection).

In 90-95 per cent of cases, the bacteria never cause any further problems, but in about five-10 per cent of infected people, they eventually start to multiply and cause active disease especially in a person with impaired immune system - for example elderly, person with HIV/AIDs, the use of corticisteroids, person with chronic disease such as diabetes.
Tuberculosis primarily affects the lungs (80 per cent) but can also affect other parts of the body like the bones, skin, lymph nodes, gastrointestinal system and other organs.

Symptoms & Complications

Prolonged cough more than two-three weeks, is the most common symptoms of tuberculosis especially pulmonary tuberculosis.

The cough may produce a small amount of green or yellow sputum in the morning.
Eventually, the sputum may be streaked with blood.

Rapidly developing shortness of breath plus chest pain may also be symptoms of pulmonary tuberculosis.

People may awaken in the night and be drenched with a cold sweat, with or without fever.
People also feel generally unwell, with decrease energy and appetite. Weight loss often occurs.

Diagnosis
When people have symptoms that suggest tuberculosis, the following may be done: Chest x-ray; tuberculin skin test; blood tests; and microscopic examination and culture of sputum sample and other suspected specimens.

The sputum and other suspected specimens are examined under the microscope to look for tuberculosis bacteria and are used to grow bacteria in a culture.

Microscopic examination provides results much faster than a culture but is less accurate. It detects only half the cases of tuberculosis identified by culture.

However, traditional cultures do not provide results for many weeks because tuberculosis bacteria grow slowly. For this reason, treatment of people who may have tuberculosis is often begun while doctors wait for results of culture.

Treatment

People who are diagnosed with active tuberculosis are required to take medications to kill the bacteria.

The most commonly used anti-TB treatment are isoniazid, rifampicin, pyrazinamide and ethambutol which are taken orally.

Streptomycin is sometimes added to the regimen.

All of these drugs have side effects, but 95 per cent of people with tuberculosis are cured and do not experience any serious side effects. Because tuberculosis bacteria are very slow-growing, anti-tuberculosis treatment must be taken for a long time - usually six months (the first two months, four different types of anti-TB treatment are taken daily followed by continuation phase, two different types of anti-TB treatment are taken thrice weekly).

To avoid poor compliance, the World Health Organisation (WHO) has recommended implementation of DOTS.

What is DOTS?
DOTS or Directly Observed Treatment Short-Course has been the internationally recommended strategy to control TB since the early 1990s.

DOTS aims to decrease TB-related morbidity, prevent TB deaths, decrease TB transmission and avoid the development of drug-resistant TB.

Patients undergoing DOTS therapy will be observed by a medical professional or a trained supervisor while they take medication.

This ensures that the correct dosage of the drug is taken at the right time and also to be certain that patients do not vanish partway through treatment.

There are five elements of DOTS:
- Political commitment with increased and sustained financing;
- Case detection through quality-assured bacteriology;
- Standardised treatment with supervision and patient support;
- An effective drug supply and management system, and;
- A monitoring and evaluation system, impact measurement span.

Since 2000, Brunei Darussalam has implemented DOTS and the DOTS coverage has been 100 per cent in all the four districts. Each health centre has a trained DOTS medical personnel to supervise patients with tuberculosis while taking their anti-TB treatment.

Prevention
There are two aspects of prevention of TB: stopping the spread of infection; and treating early infection before it becomes active disease.

Stopping the spread of infection

Allowing good ventilation with fresh air will lower the concentration of bacteria and limits their spread. Also, allowing sunlight to enter houses can kill airborne tuberculosis bacteria.

Visitors visiting TB patients in the ward should wear masks to prevent them from getting infected by the bacteria.

Healthcare workers who handle samples of infected tissue or interact with people who may be infected with TB should also wear masks to help protect them.

People with active tuberculosis especially those with pulmonary TB need to be isolated such as in isolated ward, to reduce the spread of the airborne tuberculosis bacteria and they are also required to wear masks during isolation.

Treating early infection
People who have close contact with TB patients (especially pulmonary TB) will need to go for tuberculin skin test to find out whether they are infected with tuberculosis bacteria. And if they have positive tuberculin test (that is, latent TB infection), they should be treated with drugs that will prevent them from developing into active TB disease.

Isoniazid is very effective at stopping the infection before it becomes active disease. It is given daily for six to nine months.

Administration of BCG (Bacille Calmette-Guerin) vaccine at birth has been practiced in some countries especially in countries where the likelihood of contracting tuberculosis is high.

It is given to prevent development of serious complications among children, such as meningitis.

Conclusion
Tuberculosis is one of the oldest diseases known. In most countries, tuberculosis is stigmatised, and many people are reluctant to believe that they even have latent infection.
Individuals who have symptoms of TB are advised to seek for further examination at the nearest health centres.

Tuberculosis is curable but it can be fatal if left untreated.

Ministry of Health Public Awareness Programme

Source: Weekend, 9 May 2009