Tuberculosis Declines in the US but Remains a Global Health Threat

by Jacqueline Epstein

By the beginning of the 19th century, tuberculosis (TB) had killed one in seven people who ever lived.1 The disease is caused by a bacterium called Mycobacterium tuberculosis, which is spread through the air from one person to another. While not every single person infected by the bacterium contracts the disease, people with a weakened immune system have a significantly heightened risk. In those infected, TB mainly attacks the lungs, causing fatigue, weight loss, the coughing up of blood and, ultimately, death if left untreated.2 Once a common killer in the United States with no known cure, the disease is now thought to be completely eradicated by many Americans.

The first case of TB was reported in 1768 by the Encyclopedia Britannica, describing TB as a disease that consumes the lungs. This caused the infection to be commonly referred to as “consumption.” Throughout the 19th and early 20th centuries, TB was responsible for one quarter of the deaths in Europe.3 The first successful vaccine emerged in 1921, when French bacteriologists Albert Calmette and Camille Guérin used a strain of live, attenuated M. tuberculosis to develop the Bacillus Calmette– Guérin (BCG) vaccine.3 A second successful vaccine emerged in 1943, when microbiologist Selman A. Wakman witnessed the destruction of the TB bacterium by a separate strain of bacterium named streptomycin.1 These two drugs were administered nationwide in the mid 20th century, significantly abating the epidemic. Combined with other novel antibiotics, these treatments proved to be so effective that by 1968, the number of TB cases halved since 15 years earlier in 1953. Health officials in the US declared TB to be on the verge of complete eradication.1

So why does TB remain a global threat in the 21st century? Despite previous success in curing the disease, the World Health Organization (WHO) declared TB a global emergency in 1993, with 8 to 10 million cases being reported each year.4 Particularly in Africa, a large contributor to the resurgence of TB was the emergence of the human immunodeficiency virus (HIV), which leads to the progressive failure of the immune system. A weakened immune system greatly increases an individual’s susceptibility to M. tuberculosis infection. Poverty and lack of access to basic resources also promote low immunity in populations, which explains the prevalence of TB in developing nations.4 While successful vaccines have been propagated worldwide, the course of treatment is long and costly. Vaccines such as BCG only assure protection for 10-20, creating the possibility of reinfection.4 Further, the rise of drug resistant strands of TB has diminished the efficacy of existing vaccines. Random mutations in the M. tuberculosis genome have allowed the bacterium to develop increased virulence and ability to withstand treatment with antituberculosis drugs. In particular, lineages derived from the Beijing genotype of M. tuberculosis, which is characterized by 53 different mutations largely traced to the regulatory region of the genome, have been associated with the multi-drug resistant strain of TB throughout Asia, Europe, and Africa.5

Declining rates of TB in the US over the past few decades have decreased national awareness of the global epidemic.6 Current efforts to eradicate the disease focus on optimizing screening and treatment in high-risk groups, and on investing in new research and tools, particularly to target multi-drug resistant TB strains. Future efforts to eradicate TB must also address the causes behind higher susceptibility in certain populations, such as the prevalence of HIV.

Jacqueline Epstein ’18 is a sophomore in Leverett House.

Works Cited

  1. “Timeline: Tuberculosis in America.” PBS. WGBH Educational Foundation. http://www.pbs.org/wgbh/americanexperience/features/timeline/plague-timeline/ (accessed 15 Oct. 2015).
  2. “Basic TB Facts.” CDC. Centers for Disease Control and Prevention. http://www.cdc.gov/tb/topic/basics/default.htm (accessed 15 Oct. 2015).
  3. “Tuberculosis (TB) Fast Facts.” CNN. http://www.cnn.com/2013/07/02/health/tuberculosis-tb-fast-facts/ (accessed 15 Oct. 2015).
  4. Sohail, M. J Mol Genet Med 2006 2(1), 87-88.
  5. Borgdorff, M.W. et al. Clinical Microbiology and Infection. 2013, 19(10), 889-901.
  6. Bernstein, Lenny. “Vast Majority of U.S. Tuberculosis Cases Come from Abroad, but Rate Still down.” The Washington Post. 19 Mar. 2015. https://www.washingtonpost.com/news/to-your-health/wp/2015/03/19/tb-still-declining-in-the-u-s-most-cases-brought-in-fromabroad/ (accessed 15 Oct. 2015)

 

 

Categories: Fall 2015

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