FIND Diagnostics - Tuberculosis: Background

Tuberculosis (TB) is an airborne disease caused by a pathogen belonging to the species Mycobacterium tuberculosis. Infection is spread through aerosols released in the air when a contagious person speaks, coughs, sneezes or even sings.

According to the WHO, approximately one-third of the world’s population is afflicted with the bacillus that causes TB but most of the infections do not lead to ill health or so-called “active” TB, i.e., when individuals develop clinical signs and symptoms, such as a persistent or bloody cough, weight loss, night sweats and loss of appetite, and become contagious to others.

Approximately 8.8 million new cases of TB occur each year worldwide. Sub-Saharan Africa and Southeast Asia bear the highest number of cases, accounting for one-third of the global incidence of tuberculosis.

Tuberculosis is the world’s second deadliest infectious disease — following HIV/AIDS — responsible for the deaths of nearly 1.6 million people each year. As the leading infectious killer of people living with HIV/AIDS, TB deaths have quadrupled over the past 15 years in African countries suffering the highest rates of TB/HIV co-infection.

Although men have higher rates of TB, some studies show that women of reproductive age who are infected are more susceptible to developing active TB than men in the same age group. According to the World Health Organization (WHO), tuberculosis is the leading cause of death worldwide among women in their reproductive years, causing more deaths than all other causes of maternal mortality combined. As HIV rates continue to grow, TB rates among women will continue to rise as well.

Tuberculosis also affects children. More than 250,000 children die of tuberculosis every year. Children are more likely than adults to develop “active TB” because their immune systems are not fully developed. They are also more likely than adults to develop extra-pulmonary (outside the lungs) tuberculosis, which is not only difficult to diagnose but can lead to disfigurement, paralysis and death. In addition, children who are infected with HIV are at a higher risk than HIV-infected adults of developing TB meningitis (inflammation of the lining around the brain and spinal cord due to TB bacteria), which often results in deafness, blindness, paralysis and mental retardation.

Many people affected by HIV in developing countries develop TB as the first manifestation of AIDS. The two diseases represent a deadly combination, as they are more destructive together than either disease may be alone.

Some key facts about tuberculosis

One-third of the 33 million people worldwide who are living with HIV/AIDS are co-infected with TB.

TB in HIV-positive people is almost certain to be fatal if undiagnosed or left untreated.

People who are infected with HIV are highly susceptible to TB infection due to their immune system’s inability to fight off disease.

In general, while approximately 10 percent of those who become infected will develop active TB, HIV-positive people are 50 times more likely than HIV-negative people of developing the active form of the disease.

Just as HIV heightens the risk of developing active TB, so does TB accelerate the progression of HIV into AIDS. Without proper treatment, approximately 90 percent of HIV-positive people die of TB within months of infection.

TB and poverty come together to perpetuate a vicious cycle. Poverty contributes to the spread of tuberculosis as people are forced to share close living quarters and are often in overall poor health. Simultaneously, costs associated with diagnosis and treatment create further hardship, both for patients and their families – including their children.

Worldwide, TB creates hundreds of thousands of orphans, increases child malnutrition and forces many children to leave school in order to work or care for the family or because of the stigma associated with the disease.

Better TB diagnostics — that are rapid, practical and accurate in resource-poor settings — are critical to ensuring that people receive proper and timely treatment.

New TB drugs — that will shorten treatment, be effective against susceptible and resistant strains, be compatible with antiretroviral therapies used for HIV/AIDS and that will improve treatment of latent infection — will dramatically improve TB treatment and control.

A new vaccine — that is both effective and safe for children, adolescents and adults, including people infected with HIV — will decrease TB incidence overall and, along with an effective drug therapy, could eventually control the disease.