Tuberculosis is a contagious disease which is spread through the air when people who have the active form of the disease cough or sneeze. Mycobacterium tuberculosis, the causative agent of the disease, infects many people but causes active disease in a relatively small percentage – between 5 and 10 percent – of those who are otherwise healthy. Most people who carry the bacteria suffer no obvious symptoms and cannot pass the disease to others during this latent phase of the infection. But if the immune system is weakened, the bacteria – which reside walled off in cells in the lungs – emerge to cause active TB. This occurs most prominently when individuals contract HIV/AIDS, which severely weakens the immune system (see TB & HIV/AIDS).
Tuberculosis is currently a global health problem of monumental proportions: of 6 billion people in the world, approximately 2 billion people have been infected with M. tuberculosis. Each year, the World Health Organization (WHO) estimates that 8 million new cases of TB develop and 2 million people die of the disease. The worldwide pandemic of TB continues largely unabated in spite of increased attention to the disease globally, the expansion of DOTS (Directly Observed Therapy – Short course) therapeutic regimes, and the widespread use of an existing vaccine against TB.
In March 1993, the World Health Organization designated tuberculosis a global public health emergency. Ninety-nine per cent of the estimated 2 million TB deaths and 95% of the 8 million new cases each year occur in low and middle-income countries comprising 85% of the world’s population. TB is now a leading cause of severe disease and death in the developing world. The recent increase of TB in developing countries has been exacerbated by many causes including pandemic HIV, war and political instability, drug resistance, and increasing poverty.
TB was uncommon in Africa and Asia prior to its rapid rise in the 19th and early 20th centuries following introduction by Westerners (see TB Epidemiology). By 1997 the global incidence of TB was estimated at 8 million new cases including 3.5 million highly infectious cases with fatality rates of 23%, exceeding 50% in countries with high HIV prevalence. Africa has the highest regional incidence rate of TB in the world. With the global burden of TB increasing at 3% per year, 10.2 million new cases are expected to occur in 2005. Incidence trends are increasing fastest in African countries affected by HIV (10% per yr), followed by Eastern Europe and the former Soviet Union plagued by multi-drug resistance (8% per yr) and the Americas and Asia (1-3% per year). Because it largely affects individuals in the prime years of their lives, TB has a profoundly negative impact on families, education, productivity and the entire social fabric of society. If multi-drug resistant TB increases, TB could become even more difficult to control throughout the world.
BCG (Bacille Calmette-Guerin), developed in the early 1900s, is the vaccine used against TB today (see TB Vaccines). It is widely administered to infants throughout the world, but not in the U.S. and parts of Europe where TB is mainly controlled with drugs. BCG appears to reduce the risk of serious childhood forms of TB, but protection against pulmonary TB in adults is a controversial subject with numerous studies providing conflicting results. However, the high incidence of TB in developing countries where infant BCG immunization is widely practiced indicates that BCG is not highly efficacious over the many years that people are at risk for contracting the disease.
Clearly a better vaccine against TB is urgently needed. Modeling studies show that a modestly effective vaccine (50% - 70% efficacious) used in combination with drug therapy could save tens of millions of lives, and a highly effective vaccine could eventually control the disease.
Aeras Global TB Vaccine Foundation is the only organization solely dedicated to developing a better way to vaccinate against tuberculosis. Working collaboratively with individual scientists, academic institutions, industry, and government agencies in the U.S., Europe, South Africa, and other developing countries, Aeras aims to bring leading TB vaccine candidates to Phase I, II, and III clinical testing over the next several years and to license and manufacture at least one new TB vaccine for worldwide distribution by 2014.
For more information about TB:
World Health Organization Fact Sheet on Tuberculosis: http://www.who.int/mediacentre/factsheets/who104/en/
NIAID Tuberculosis Fact Sheet:
A History of Tuberculosis Treatment: http://www.umdnj.edu/~ntbcweb/history.htm
NIAID Focus on Tuberculosis: