Reasons why Tuberculosis has not been eradicated from the world by now

Despite a cure, and a vaccine- BCG, why does TB continue to haunt people, throughout the world, and is still a large section of health care policies by governments and WHO?

Tuberculosis, a bacterial disease, spreads through surface contamination and air borne droplets given out by sneezing and coughing, very similar in spread method to the regular flu everyone experiences. The difference between the two is of the severity, and the time span of infection. Although it has an infection rate lower than many pathogens which spread by the same route, for Eg influenza virus, swine flu and Sars Cov-2, it infects a large number of people annually, and as of now, it affects, directly or indirectly a quarter of human population.

Despite a cure, and a vaccine- BCG, why does TB continue to haunt people, throughout the world, and is still a large section of health care policies by governments and WHO? Why is the disease of Tuberculosis not eradicated by now, even after such extensive funding, countless dedicated health workers and hardworking organizations that meticulously plan and coordinate our steps towards a potential tuberculosis free world?

There are numerous reasons as to why has tuberculosis not been eradicated yet. The reasons or issues can be divided into some broad categories, as given in the diagram below:

Now, let’s discuss each reason in brief.

1) Nature of disease and mode of infection Tuberculosis spreads by surface contamination and aerosols generated while coughing, sneezing or even talking. This makes it very difficult to control the spread of tuberculosis among people related to an infected person.

Adding to this woe, TB requires very low number of bacterium bodies (as less as 10) to kickstart the disease in humans. Hence, even a low exposure has the potential to infect a person and spread further.

Additionally, it has a slow growth rate in the body and hence can take months to years to develop fully and manifest symptoms. Meanwhile, it can spread to other people even when the first person is asymptomatic. Hence, it spreads before detection in majority of the cases. Fortunately, this cloud has a silver lining because according to a WHO report, at least 1/3rd of the world population carries the TB bacteria- MT, but not all get severe disease and stay asymptomatic.

A big advantage the bacteria has over the healthcare services is that its symptoms, generally resembling those of common seasonal flu. This leads to lack in detection as people are hesitant testing themselves. This further aides the spread of tuberculosis in the community.

2) Effectiveness of vaccine in adults BCG, the vaccine for tuberculosis is found to provide effective protection when administered in infants. Still, this protection does not last lifelong. When administered in adults, it does not provide enough immunity for long.

3) The long duration of cure- DOTS One might think, if the spread can be controlled neither by vaccination, nor by detection, we can cure it by medication, as it is available throughout the world. Hence, the disease can be treated in a period of 6 to 9 months, with simple ingestible tablets. The issue in this aspect, is not due to the pathogen, but due to people’s attitude and carelessness. In majority of the cases, patients stop the medication as soon as they get relieved of the symptoms. This leads to incomplete treatment, leading to futility of efforts.

4) Prevalence in socially and economically backward regions On of the distribution statistic is that in any given country, TB is more prevalent in the socially and economically backward regions. The major reason thought for this skewed ratio is thought to be the lack of knowledge about the disease and available facilities and treatments.

There are many pre-set stigmas in rural areas, which cause people to avoid tests when they display symptoms. Even if someone tests positive, he/she is reluctant to take medications on a regular basis. On of the examples is the Sub-Saharan Region, which has a known case density of over 300 per 1,00,000 people.

Also, rural areas make it difficult to educate people, mobilize resources and to utilize them to their fullest potential. For example, it is difficult to maintain cold chain for vaccine distribution in backward regions, leading to high wastage.

Also, as large corporate hospitals and private practitioners are reluctant to work in rural areas due to lack of infrastructure and income prospects, the onus to drive such anti-TB campaigns lies on the resources and manpower of governments and various NGOs. This limits the coverage of any campaign in such areas. This pushes the TB drive backwards in rural regions.

5) MDR-TB Another hurdle in eradicating tuberculosis is the emergence of “Multi-drug Resistant Tuberculosis”. This type does not respond to the regular medication like isoniazid and rifampin.

These strains emerge when the patient does not complete the entire prescribed course of a given medicine, or the available drug is of low quality. In some cases, MDR-TB might occur as a result of incorrect medication being referred to the patient.

6) Other related and non-related infections Other diseases play an important role in eradication and control of TB in regions of prevalence. Any new epidemic/endemic disease bring the need of new funds, trained as well as untrained manpower. This diverts resources from other long term policies such as the ones against TB and HIV.

There are various examples of these type of setbacks in our fight against Tuberculosis, such as the Ebola virus in Western Africa and the SARS epidemic in China. We also have a recent example in the form of the SARS COV-2 virus, which has caused an epidemic and brought to knees, the various efforts put in by the governments, against diseases, both infectious and non-infectious, by virtually bringing the world to a halt and centralizing the whole of our healthcare resources towards itself.

This pandemic has set us back by many years in our resistance against Tuberculosis, as cases were underreported and the cases, not managed well enough, as depicted by this image from a WHO report.

Other infections strengthen TB by other means as well. For instance, a person infected with HIV is a lot more susceptible to TB, and can develop a severe disease rapidly.

EFFECT DUE TO THE COVID-19 PANDEMIC There are two schools of thought, on the effect of the COVID-19 pandemic on the spread and control of TB. The first points out that the extra measures taken by the general public, like masking, proper hand and oral hygiene habits, and also by the authorities, by keeping the public places clean and enforcing appropriate guidelines. This line of thinking leads to the conclusion that the TB spread will be reduced significantly as compared to the previous years, thus helping us in a way.

The second school of thought emphasizes on the lack of attention towards TB detection and control, and the shortage of manpower, funds and resources to keep a tab on the case count of TB. This line of thought leans towards the belief that due to the pandemic induced supply chain disruption, we might see a silent surge in TB cases in the coming years, when the detection and testing for TB returns to pre- pandemic levels.

Comparing both, the second school of thought seems dominant and seems to have more effect. Because, even if the detections are low, the actual cases might be up, without us having any knowledge about it. Also, the pandemic caused a hurdle in completing the medicine course of already detected patients, as proper follow-ups could not be done by the medical service providers. The graph below indicates the drop in registration and course completion in India. A similar trend is observed globally.


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