Tuberculosis (TB) kills approximately 2 million people each year. The global epidemic is growing and becoming more dangerous. The breakdown in health services, the spread of HIV/AIDS and the emergence of multidrug-resistant TB are contributing to the worsening impact of this disease.
In 1993, the World Health Organization (WHO) took an unprecedented step and declared tuberculosis a global emergency, so great was the concern about the modern TB epidemic.
It is estimated that between 2002 and 2020, approximately 1000 million people will be newly infected, over 150 million people will get sick, and 36 million will die of TB - if control is not further strengthened.Infection and Transmission
TB is a contagious disease. Like the common cold, it spreads through the air. Only people who are sick with pulmonary TB are infectious. When infectious people cough, sneeze, talk or spit, they propel TB germs, known as bacilli, into the air. A person needs only to inhale a small number of these to be infected.
Left untreated, each person with active TB will infect on average between 10 and 15 people every year. But people infected with TB will not necessarily get sick with the disease. The immune system ''walls off'' the TB bacilli which, protected by a thick waxy coat, can lie dormant for years. When someone''s immune system is weakened, the chances of getting sick are greater.
- Someone in the world is newly infected with TB every second.
- Nearly 1% of the world''s population is newly infected with TB each year.
- Overall, one third of the world''s population is currently infected with the TB bacillus.
- 5-10% of people who are infected with TB (but who are not infected with HIV) become sick or infectious at some time during their life.
Global and Regional Incidence
Each year, more people are dying of TB. In Eastern Europe and Africa, TB deaths are increasing after almost 40 years of decline. In terms of numbers of cases, the biggest burden of TB is in south-east Asia.
Factors Contributing to the Rise in TB
- TB kills about 2 million people each year (including persons infected with HIV).
- More than 8 million people become sick with TB each year.
- About 2 million TB cases per year occur in sub-Saharan Africa. This number is rising rapidly as a result of the HIV/AIDS epidemic.
- Around 3 million TB cases per year occur in south-east Asia.
- Over a quarter of a million TB cases per year occur in Eastern Europe.
HIV is accelerating the spread of TB
HIV and TB form a lethal combination, each speeding the other''s progress. HIV weakens the immune system. Someone who is HIV-positive and infected with TB is many times more likely to become sick with TB than someone infected with TB who is HIV-negative. TB is a leading cause of death among people who are HIV-positive. It accounts for about 11% of AIDS deaths worldwide. In Africa, HIV is the single most important factor determining the increased incidence of TB in the past 10 years.
Poorly managed TB programmes
Until 50 years ago, there were no drugs to cure TB. Now, strains that are resistant to a single drug have been documented in every country surveyed and, what is more, strains of TB resistant to all major anti-TB drugs have emerged. Drug-resistant TB is caused by inconsistent or partial treatment, when patients do not take all their drugs regularly for the required period because they start to feel better, doctors and health workers prescribe the wrong treatment regimens or the drug supply is unreliable.
A particularly dangerous form of drug-resistant TB is multidrug-resistant TB (MDR-TB), which is defined as the disease due to TB the two most powerful bacilli resistant to at least isoniazid and rifampicin anti-TB drugs. Rates of MDR-TB are high in some countries, especially in the former Soviet Union, and threaten TB control efforts.
From a public health perspective, poorly supervised or incomplete treatment of TB is worse than no treatment at all.
Effective TB Control
The WHO-recommended treatment strategy for detection and cure of TB is DOTS. DOTS combines five elements: political commitment, microscopy services, drug supplies, surveillance and monitoring systems and use of highly efficacious regimes with direct observation of treatment.
Once patients with infectious TB (bacilli visible in a sputum smear) have been identified using microscopy services, health and community workers and trained volunteers observe patients swallowing the full course of the correct dosage of anti-TB medicines (treatment lasts six to eight months).