The Triple Helix @ UChicago

Fall 2016

"TB: A Global Health Issue" by Kalina Kalyan

 

Tuberculosis, commonly abbreviated as “TB,” is a top ten cause of death across the world. Tuberculosis is caused by a bacteria known as Mycobacterium tuberculosis.[1] Worldwide, one in three people alive today are thought to be infected with Mycobacterium tuberculosis (Mtb) during the course of their lives. However, most are unaware of the presence of Mycobacterium tuberculosis in their lungs because the pathogen is typically kept “in check” by the body’s immune system. This is known as latent TB. In people infected with latent Mtb, symptoms are not shown and the only sign of TB is through the tuberculin skin test or through the TB blood test. Although those with latent TB will show a positive result for these tests, the presence of Mtb does not mean that one will be infected with active TB.[2] Those who are infected by latent TB have a ten percent risk of contracting active TB. When a person has active TB, they exhibit symptoms and are able to pass the disease on to other people. 

Once a person contracts active TB, symptoms will often appear two to three months after exposure. However, sometimes symptoms can take years to appear. These symptoms commonly include cough, fever, night sweats, and weight loss. Oftentimes, those infected with TB don’t immediately notice their symptoms, as the severity of the illness escalates with time. This delay also leads the infected to postpone seeking treatment, thus resulting in the unknowing transmission of the bacteria to others. In a year, those with active TB can affect 10-15 people with whom they are in close contact. 

TB is most prominent in six countries; India, Indonesia, China, Nigeria, Pakistan and South Africa. These six countries compose 60% of the total cases of TB. It has been found that over 95% of TB deaths take place in low to middle income countries. Contraction of TB is highly related to nutrition status and is considered a “poor man’s disease.” Lack of proper nutrition and sanitary conditions in the countries where the disease is most prominent continues to contribute to the presence of TB. Poverty and poor access to service challenges the successful treatment of those with TB. 

Impoverished countries tend to have higher rates of both TB and HIV. Those who are infected with HIV are at a much higher risk of contracting the disease than those who are not.[1] HIV and TB are so closely connected that their relationship is often deemed “co-epidemic.” In 2015, at least a third of people living with HIV were infected with Mycobacterium tuberculosis. These people have a 20 to 30 times higher risk of developing active TB than those who do not have HIV. In recent studies, the correlation between HIV and TB has been further explored. HIV and TB are a deadly combination in which the contraction of one speeds up the growth of the other. In 2015 alone, there were 1.2 million cases of TB amongst those living with HIV. People with advanced HIV infection are vulnerable to a wide range of infections called “opportunistic infections.” Opportunistic infections are infections that essentially take advantage of the opportunity offered by an already weakened immune system. TB is an HIV related opportunistic infection. 

It is commonly thought that as HIV progresses, the immune system is generally weakened. However, it has been proposed that as HIV advances, the immune system’s focus is weakened through its attention to antiviral responses. This attention on antiviral responses makes it difficult for the immune system to defend the body against the Mtb pathogen, which is bacterial.[2] 

A vaccine formulation has been created in Fudang University in Shanghai that claims to act against both HIV and Mtb simultaneously. This vaccine contains antigens from both of the pathogens of Mtb and HIV and induces a cellular immune response.[3] It is important to note, however, that this vaccine is only effective in those affected by Mtb and not active TB. 

Those not infected with HIV but who are infected with active TB have several treatment options through antibiotics. A combination of drugs is necessary to actively combat TB as taking more than one drug better kills the bacteria and is more likely to prevent the patient from becoming resistant to the drugs. To ensure thorough treatment, it is often recommended that a patient take his or her pills in the presence of someone who can supervise treatment. This approach is known as DOTS (directly observed treatment, short course). DOTS cures TB in 95% of cases and in some parts of the world this treatment costs as little as $10 for a six month supply. A vaccine called BCG is available for the prevention of TB. However, this vaccine was first used in the 1920s and studies have shown it to be very variable in its ability to effectively protect people from the disease in modern day. BCG can also cause false positive TB readings and can lead to a fatal disease called disseminated BCG, in those with weakened immune systems. A drug known as isoniazid can be used as a preventative measure for those at high risk of contracting TB. Those who have inactive TB can take a course of isoniazid for several months in order to prevent active TB.[6] 

TB is both preventable, and curable. However, it continues to be a major global health issue. TB treatment depends largely upon the responsibility of the patient and healthcare professionals. Treatment is only effective when antibiotics are taken for several months. An incomplete treatment can lead to drug resistant TB which poses a number of even more grave concerns. The connection between impoverished countries and presence of TB is undeniable. Several factors such as malnutrition, unsanitary conditions, and lack of proper health care contribute heavily to the spread of TB. These conditions cannot be neglected by countries that have nearly eliminated the presence of TB within their borders.[4] 

In countries that have not yet been able to successfully eliminate the presence of TB, there is a prominent connection between stigma and cases of active TB. Treatment for active TB involves isolation and daily visits to health care professionals. These aspects of treatment can cause many patients to feel uncomfortable completing their treatment as they may feel like an “outcast” or even be rejected by their families and friends. This stigma that surrounds TB can eliminate an infected person’s desire to even see a physician or seek help out of fear for being deemed “contagious.” India is one of such countries that still possesses a significant amount of stigma towards those with TB, despite bearing one third of the world’s TB burden. In India it is common for those with TB to experience social isolation and rejection. This leads to people with TB hiding their symptoms and failing to receive adequate treatment. If this stigma were to be eliminated, or even reduced, the number of TB cases would decrease significantly as those who need treatment would live in less fear. The public is frequently misinformed about TB and although it is important that research of TB be continued, in order to relieve this burden the stigma surrounding the disease must be targeted effectively and health education must continue to be expanded.[5]

References

[1] “Tuberculosis” World Health Organization. Last modified October 2016 http://www.who.int/mediacentre/factsheets/fs104/en/ 
[2] Lucy C. K. Bell “In Vivo Molecular Dissection of the Effects of HIV-1 in Active Tuberculosis.” PLOS Pathogens, 2016; 12 (3): e1005469 DOI: 10.1371/journal.ppat.1005469
[3] “Experimental vaccine elicits robust response against both HIV and tuberculosis, study suggests” Science Daily, May 21, 2012.https://www.sciencedaily.com/releases/2012/05/120521152645.htm
[4] Sandro Galea. “The Unnecessary Persistence of Tuberculosis.” The Huffington Post. Last modified October 26, 2016. http://www.huffingtonpost.com/sandro-galea/the-unnecessary-persisten_b_12661768.html
[5] Anita S. Mathew and Amol M. Takalkar “Living with Tuberculosis: The Myths and the Stigma from the Indian Perspective” Oxford Journals. 2007. http://cid.oxfordjournals.org/content/45/9/1247.full
[6] “HIV/TB Co-infection” Aids Centre. Last modified 2010. http://aids.md/aids/index.php?cmd=item&id=276

 
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