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 World Health Organization (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 others1.

There were 9.4 million new cases of TB across the globe in 20082. Sub-Saharan Africa and Southeast Asia bear the highest number of cases. Of these 9.4 million cases, approximately 1.2-1.6 million were HIV-positive1. WHO estimates that there were 0.5 million cases of multidrug-resistant TB (MDR-TB) in 2007 and 5% of all TB cases have MDR-TB1. Up until now, cases of extensively drug-resistant TB (XDR-TB) have been reported in 57 countries2.

 

 Worldwide Distribution of New TB Cases, 2006

Source: WHO

Tuberculosis is the world’s second deadliest infectious disease — following HIV/AIDS — responsible for the deaths of approximately 1.6 million people in 20053. 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-infection4.

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 WHO5 tuberculosis is the third leading cause of death worldwide among women in their reproductive years. As HIV rates continue to grow, TB rates among women will continue to rise as well.

Tuberculosis also affects children. According to WHO over 250,000 children develop TB and 100,000 children will continue to die each year from TB6. 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 facts about tuberculosis

  • Approximately one-third of the 33 million people worldwide who are living with HIV/AIDS are co-infected with TB and one in four HIV-positive people die due to TB7.
  • TB in HIV-positive people is almost certain to be fatal if undiagnosed or left untreated8.
  • People who are infected with HIV are highly susceptible to TB infection due to their immune system’s inability to fight off disease8.
  • Those people living with HIV are 20 to 30 times more likely to develop TB than those who do not carry the virus7.
  • 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 infection8.
  • Multidrug-resistant TB occurs when patients fail to respond to standard first-line drugs, while extensively drug-resistant TB occurs when resistance develops to second-line drugs in addition to MDR-TB8.
  • 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 treatments create further hardship, both for patients and their families – including their children11.

 

To stop the spread of TB globally, the world needs:

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.

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References

1. WHO Stop TB Partnership (2009) 2009 update TUBERCULOSIS FACTS http://www.who.int/tb/publications/2009/tbfactsheet_2009update_one_page.pdf  

2. WHO (2009) Global Tuberculosis Control, A short update to the 2009 report. http://whqlibdoc.who.int/publications/2009/9789241598866_eng.pdf

3. WHO (2007) Tuberculosis Fact Sheet No. 104
http://www.who.int/mediacentre/factsheets/fs104/en/print.html 

4. WHO (2005) TB EMERGENCY DECLARATION issued by WHO Regional Office for Africa
http://www.who.int/tb/features_archive/tb_emergency_declaration/en/index.html

5. WHO (2009) Women’s Health Fact Sheet No. 334
http://www.who.int/mediacentre/factsheets/fs334/en/index.html  

6. WHO (2009) TB/HIV brochure – NO more people living with HIV dying of TB http://www.who.int/tb/challenges/hiv/tbhivbrochure.pdf  

7. WHO (2010) Frequently asked questions about TB and HIV
http://www.who.int/tb/challenges/hiv/faq/en/index.html

8. WHO (2009) TB/HIV FACTS 2009 http://www.who.int/tb/challenges/hiv/factsheet_hivtb_2009update.pdf

9. WHO SEARO (2006) TB and Children Fact Sheet http://www.searo.who.int/en/Section10/Section2097/Section2106_10681.htm  

10. WHO (2007) WHO European Ministerial Forum – All Against Tuberculosis, Tuberculosis and HIV infection, EUR/TB/FS04, 3 September 2007 http://www.euro.who.int/document/TUB/fs04e_tbhiv.pdf  

11. WHO (2001) GUIDELINES for SOCIAL MOBILIZATION – A human rights approach to tuberculosis
http://www.who.int/hhr/information/A%20Human%20Rights%20Approach%20to%20Tuberculosis.pdf