The Emergence and Impact of Extensively Drug-Resistant Tuberculosis
Despite tuberculosis (TB) control programs, Mycobacterium tuberculosis remains the most common cause of infection-related mortality worldwide. In 1997, nearly 2 billion people were estimated to be infected with TB. Each year, 8-9 million individuals develop active infection, and at least 2 million people die of TB or related complications. In other words, worldwide, 1 in every 3 people is infected with TB, and 1 in every 8 deaths is a result of TB. While nearly every nation faces the burdens and risks of this disease, TB is largely a problem among developing nations, which account for 95% of cases and 98% of deaths. Historically, TB imposes a 15% overall case fatality rate. This varies from 7% in industrialized countries to 20% in Central and South America to 35% to 40% in parts of Asia and Africa. Mortality exceeds 50% in parts of Africa where resources are lacking and the prevalence of HIV infection is high.
Given the overwhelming global impact, the World Health Organization (WHO) declared TB a global public health emergency in 1993. Since then, the incidence of TB and its associated mortality have stabilized. However, despite these relative successes, we have seen the emergence of drug resistance, which now poses a significant worldwide threat.
Resistance to single antimycobacterial agents has long been recognized. Fortunately, the standardized use of multiple agents to treat active disease, the efficacy of these drugs, and the common use of directly observed therapy (DOT) have mitigated a significant impact on treatment regimens or mortality. Unfortunately, the evolution of drug resistance has led to the recent emergence of TB strains resistant to multiple agents, including those medications used as standard first-line therapies. This has forced considerable alterations in the treatment of TB and is expected to drastically worsen mortality.
Despite tuberculosis (TB) control programs, Mycobacterium tuberculosis remains the most common cause of infection-related mortality worldwide. In 1997, nearly 2 billion people were estimated to be infected with TB. Each year, 8-9 million individuals develop active infection, and at least 2 million people die of TB or related complications. In other words, worldwide, 1 in every 3 people is infected with TB, and 1 in every 8 deaths is a result of TB. While nearly every nation faces the burdens and risks of this disease, TB is largely a problem among developing nations, which account for 95% of cases and 98% of deaths. Historically, TB imposes a 15% overall case fatality rate. This varies from 7% in industrialized countries to 20% in Central and South America to 35% to 40% in parts of Asia and Africa. Mortality exceeds 50% in parts of Africa where resources are lacking and the prevalence of HIV infection is high.
Given the overwhelming global impact, the World Health Organization (WHO) declared TB a global public health emergency in 1993. Since then, the incidence of TB and its associated mortality have stabilized. However, despite these relative successes, we have seen the emergence of drug resistance, which now poses a significant worldwide threat.
Resistance to single antimycobacterial agents has long been recognized. Fortunately, the standardized use of multiple agents to treat active disease, the efficacy of these drugs, and the common use of directly observed therapy (DOT) have mitigated a significant impact on treatment regimens or mortality. Unfortunately, the evolution of drug resistance has led to the recent emergence of TB strains resistant to multiple agents, including those medications used as standard first-line therapies. This has forced considerable alterations in the treatment of TB and is expected to drastically worsen mortality.
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