Risk Factors Associated with Tuberculosis

Tuberculosis Epidemic: A Global Health Challenge

Tuberculosis (TB) is responsible for the greatest morbidity and mortality rate of any illness worldwide. Every year, the disease kills roughly 1.5 million people and creates 9.6 million new infections (WHO 2016). The disease is more prevalent in poor and densely populated areas. Furthermore, a multidrug-resistant type of Mycobacterium TB seen in most nations complicates disease control. While early detection offers a tool for diagnosis and control, the resource constraints typical in developing nations and marginalized populations make treating the infected unfeasible. In fact, over a million people worldwide are currently undiagnosed or mistreated (WHO 2016). To respond to the challenges, the World Health Organization (WHO) launched a global TB strategy that for the years beyond 2015 that was aimed at ensuring that TB epidemic will be eradicated by the year 2035 (WHO 2016). The strategy revolved around a threefold model of patient canted care and prevention, policies and supportive systems that aim at eradicating the disease, and innovative and intensive research towards its cure. Understanding the epidemiology of TB is a gateway to achieving the effective global control of the disease.

Infectious Agent

The infectious agent Mycobacterium tuberculosis causes Tuberculosis (TB). M. tuberculosis is an acid-fast bacterium that is rod-shaped, slow-growing, and non-motile (Dye & Glaziou, 2016). M. tuberculosis can get into the body of a host when an infected person coughs and releases the infectious agents into the air; another agent, Mycobacterium bovis is transmitted through consumption of dairy products such as unpasteurized milk from infected cattle. Once inside the host, M. tuberculosis attacks the lungs, and can also spread to other vital organs of the body.


The incidence rate of TB has reduced significantly over since 2000. The incidence rate recorded in 2014 stood at 1.5%, a number that was similar to the one registered in 2015. As at 2015, the reported cases of active TB stood at 10.4 million of which 1.2 million included HIV-positive people. Of the 10.4 million, 56% were men, 34% children and the rest (10%) were women. Over 60% of the new cases came from 6 countries; Nigeria, South Africa, India, China, and Pakistan (WHO, 2017). The largest incident cases, however, occurred in India, corresponding to about 26% of the global incidence cases as at 2016.
Incident cases vary from country to country. The lowest incident cases take place in economically developed countries such as the United States, Europe, Canada, New Zealand, and Australia; reporting an incidence rate of below 10 cases per 100,000 people (WHO, 2017). On the contrary, the incidence cases among the developing countries are as high as 50 cases per 100,000 inhabitants. As at 2016, the top 10 global incidence rates comprised of countries solely from Africa with Swaziland and South Africa having the largest rates (WHO, 2017); about one in every 100 people.
Around the globe, incidence rates have been steady since 1990 up to 2001, after which the rates significantly reduced to about 2% in 2013. It is notable that regions within the WHO are the fastest in the reduction of incidence; working at a reduction rate of about 6.5% each year. In comparison, countries outside the WHO have the lowest incidence rate reduction of less than 1% each year.
The incidence of the disease also varies with age. In the developing countries such as Africa, the infections are associated with young adults and adolescents. In the developed countries like the United States, the incidence rate is related to the elderly and the immunocompromised.


Every year, there are around 9 million new cases of the TB reported around the world. Among the infected community, around 1.3 succumb to death from the disease. Notably, there is a significant decrease in mortality rates across the globe since 1990: as much as 50% in 2015 as compared to a baseline measure in 1990 (Glaziou, Sismanidis, Floyd, & Raviglione, 2014). However, in the case fatality ratio stood at 17% in 2015 and 2016.
As at 2012, approximately 75% of the total TB infections and deaths came happened in Africa and South-East Asia, with South Africa and India accounting for a third of all the global deaths related to TB.
The average number of fatalities per 100,000 people around the globe stood at 13 in 2012 and had not shifted significantly since (Glaziou, Sismanidis, Floyd, & Raviglione, 2014). Among the HIV-positive population, however, the number is high, recorded at 17.6 as at 2013. In the economically developed countries (for example United States, Canada, Europe, Australia, and New Zealand), the number of deaths per 100,000 people stands at less than one person. Contrary, in developing countries, and the high burden countries, the victims per 100,000 inhabitants stands as high as 40.


In 2012, about 12 million cases of TB, and equivalent of 169 cases per 100,000 people, were reported. An observation of the global prevalence rate statistics shows that the number has reduced by as much as 37% since 1990 (Glaziou, Sismanidis, Floyd, & Raviglione, 2014). The Stop TB Partnership that was set in 1990 –halving the number of prevalence rates by 2015 – has not been met yet (WHO, 2017). There has been a minimal shift of the disease ever since. The number of infections arising from the disease has not reduced anyway as at 2016.
The Western Pacific Regions, the Americas Region, and the Southeast Asia region achieved the 50% reduction rates placed in 2012. However, Africa and the East Mediterranean regions have not been able to achieve their target, and the prevalence rates are rather increasing. Problems such as limited access to ART (antiretroviral therapy) and HIV have also contributed to the prevalence of the disease in the developing and high burden countries.

Risk Factors Associated with Tuberculosis

One is in danger of contracting the virus if he/she is living near or around people who have active TB. The infected members of the community coughing and releasing the bacteria in the air increase the possibility of the spread of TB to other people (Narasimhan, Wood, MacIntyre, & Mathai, 2013). Therefore, the inhabitants of overcrowded and poor inner town or rural cities are at a higher risk of getting the virus than those in spacious developed countries.
The TB infection risk increases with increases for the intravenous drug user, the people living or working in a homeless shelter, those in a nursing home, and those in prison or jail (Narasimhan, Wood, MacIntyre, & Mathai, 2013). Since these people are at risk of exposure to the infectious agent, the chances of acquiring the disease increase with an increase in their activities.
It is important to note that getting into contact with the bacteria does not guarantee the development of the disease. In fact, only a small number of people getting in touch with the virus develop active TB (Narasimhan, Wood, MacIntyre, & Mathai, 2013). However, certain diseases and condition increase the risk developing active tuberculosis. These include: HIV infection, having a low body weight, having cancer, and silicosis (Narasimhan, Wood, MacIntyre, & Mathai, 2013).
Among the indigenous populations in the world, the Hispanic, the Africans, the Indians, the African-American, and the Asians are among those at risk of getting the disease (Narasimhan, Wood, MacIntyre, & Mathai, 2013). Apart from that, the increased time of exposure in health care industry, extended stay in high-risk areas, and time in prison can place one at greater risk of contracting the disease.

Notification and Treatment Success

The recording and reporting of the Tuberculosis cases around the globe were an outcome of five other pillars of WHO’s TB strategy launched in the 1990s (Dye & Glaziou, 2016). The framework encourages notification and reporting of the treatment outcomes whenever possible since 1995. This framework was in action on the notification of 5.7 new cases of the 6.1 reported infections in 2012 (Glaziou, Sismanidis, Floyd, & Raviglione, 2014). India and China reported about 39% of the cases since 2013.
Of the notifications around the globe, 88% have involved persons between 15 and 64 years. The sex ratio (M/F) was stipulated at 1.7 (WHO, 2017). The majority of the TB notifications were, however, men, which the WHO could not fathom correctly. However, some of the explanations included the high-risk exposure and biological differences between men and women (Dye & Glaziou, 2016). Among regions with a great prevalence of the disease, the reported incidence between men and women is almost equal.
Of the new cases reported since 2011, over 87% have since been treated (as at 2016) (WHO, 2017). The lowest treatment success was in Africa (79%): Though there has been some notable improvement. The treatment success for MDR-TB patients has been lower in most countries reported.


As the fight towards eradication of the Tuberculosis pandemic continues, efforts from WHO and other stakeholders have shown increasing success in reducing the incidence, mortality, and prevalence rates among populations. By studying the epidemiology of the disease, the health organizations across the globe can gauge their success and formulate new policies in regions where the prevalence, incidence, and mortality rates escalate or persist.


Dye, C., & Glaziou, P. (2016). The Global Tuberculosis Epidemic: Scale, Dynamics, and Prospects for Control. Tuberculosis: The Essentials, 237, 1.

Glaziou, P., Sismanidis, C., Floyd, K., & Raviglione, M. (2014). Global Epidemiology of Tuberculosis. Cold Spring Harbor Perspectives In Medicine, 5(2), a017798-a017798. http://dx.doi.org/10.1101/cshperspect.a017798

Narasimhan, P., Wood, J., MacIntyre, C., & Mathai, D. (2013). Risk Factors for Tuberculosis. Pulmonary Medicine, 2013, 1-11. http://dx.doi.org/10.1155/2013/828939

WHO. (2016). Global tuberculosis report. World Health Organization. Retrieved 19 April 2017, from http://www.who.int/tb/publications/global_report/en/

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