Environmental Tuberculosis: causes and treatment

What is tuberculosis?

Tuberculosis (TB) is a contagious disease that can cause a serious lung infection. It can be fatal if left untreated or not treated correctly. Some patients become very ill, while others never have symptoms. Most cases can be treated successfully with antibiotics, but they must be taken for many months to kill the bacteria. An active TB infection can cause coughing, fatigue, fever, night sweats and weight loss.

TB is divided into two types, latent and active.

Latent TB infection means you have tuberculosis germs in your body. However, because of a healthy immune system, the body stops the germs from growing. You don’t have symptoms or feel ill, and are not contagious. TB germs are still alive and can become active at any time. This happens if the immune system is weakened and can no longer fight the germs. Latent TB infection requires medication to kill the bacteria and reduce the risk of later developing active TB disease. About 10% of infected people who fail to get treatment for latent TB infection will develop active TB disease at some point in their lives.
Active TB disease means TB germs are multiplying, you have symptoms, are ill, and you’re contagious. The majority of adult cases (90%) of active TB develop from latent TB infection. Besides the lungs, TB can also affect other parts of the body. Antibiotics are needed for six to 12 months to kill the bacteria and reduce the chances of infecting others.

What is environmental tuberculosis?

Environmental TB refers to factors in your environment that can cause and/or increase TB transmission, and strongly affect the outcome. Environment refers to a person’s location, their living conditions, personal habits, economic status, access to health care, plus factors in the natural world such as air and soil pollution. Environmental factors play a strong role in tuberculosis transmission, its severity, cure rates, and death rates. Understanding these environmental and social factors is vitally important for TB control and prevention programs.

What causes environmental tuberculosis?

There are many factors in a person’s living and working environment that can increase their chances of getting TB, as well as the outcome of their disease. Many of the environmental factors that increase TB cases can also contribute to a weakened immune system. It is the strength of your immune system -- its ability to fight TB germs -- that determines whether you get active TB disease right away, or stay in the latent TB infection stage for a while, or never have symptoms.

How do environmental factors increase TB?

The following factors increase the risks of TB infection by increasing the situations that bring TB-positive people in close contact with others. They also make it more likely that latent TB will progress to active TB disease. They include:

Poverty - Most of the following factors are closely tied to poverty. TB has always been a disease of the poor. Areas with the highest number of TB deaths are in the developing world or in poor, urban neighborhoods in wealthier countries. Larger families, illiteracy or low educational levels, plus inadequate health care resources also contribute to higher TB-positive rates among poorer people.
Malnutrition is a key TB risk factor. TB causes wasting, suppresses the immune system, and causes other symptoms. These symptoms are also caused by malnutrition, so it’s hard to determine if malnutrition leads to TB or vice versa.
Indoor air pollution largely comes from burning solid fuels for cooking (wood, coal, animal dung, crop residue, charcoal). Poor people usually cook indoors in poorly ventilated areas. The solid fuels produce excessive smoke containing harmful chemicals (carbon dioxide), similar to the risks of cigarette smoke. This is the chief risk factor for TB in women.
Smoking tobacco harms both the smoker and those who inhale the secondhand smoke, and reduces immune system strength. Smoking is the main risk factor for men.
Excessive alcohol use also lowers immune system strength and increases infection risks. It can increase disease progression by increasing risky social interactions that facilitate TB exposure.
Poor access to health care increases the TB risk factors of HIV infection and diabetes, and decreases the chances of successful TB treatment.

Other environmental factors that enhance TB transmission and worsen outcomes include:

Air and soil pollution - Virulent (capable of infecting someone) TB germs can live in carpet for up to 19 days, in wood for over 88 days, and in soil for up to three months, even in winter. TB germs in dust have been found to survive up to six month outside the body if not exposed to direct sunlight.
Overcrowded living conditions - A study of TB in New Zealand found that every 1% increase in the number of overcrowded households led to an 8% increase in TB cases.
Urbanization (along with poverty) creates the perfect conditions to enhance TB transmission and increase progression of latent TB to active TB disease. Urbanization and poverty lead to greater population density, crowded living conditions, and increased mobility of people, especially among migrants.

What are the symptoms of environmental tuberculosis?

Active TB disease symptoms largely affect the lungs and may include:

Coughing that lasts more than three weeks
Coughing up blood or mucus
Chest pain, especially when you breathe or cough
Fatigue
Night sweats
Fever and chills
Loss of appetite and unintentional weight loss

TB can also affect lymph nodes, bones, brain (causing back pain), spine, kidneys (causing blood in your urine), and skin (rash). Unless TB is in the lungs, it’s usually not contagious.

Latent TB infection does not cause symptoms or illness.

How is environmental tuberculosis diagnosed?

TB is diagnosed with:

Skin test - a small amount of fluid is injected into the skin, and you will be checked for swelling in two to three days. Accuracy is reduced if you very recently got TB, or have had a TB vaccine (BCG).
Blood test - your blood sample is mixed with TB proteins and the response is measured.

If you get a positive test result, your doctor will test further to determine if you have active or latent TB. Additional testing is done by:

Chest X-ray or CT scan to look for changes in your lungs
Acid-fast bacillus (AFB) test looks for TB bacteria in your sputum

How is environmental tuberculosis treated?

A combination of antibiotics taken every day for at least six to 12 months will cure most active TB cases. In poorer populations, it can be difficult to get compliance with this difficult treatment regimen.

Active TB disease requires several weeks of antibiotic treatment before the patient isn’t contagious. During the contagious period, precautions are needed to protect others. However, in poorer areas, isolating the patient, wearing face masks, and improving ventilation is generally not possible.

Why should I worry about environmental tuberculosis?

Environmental and socio-economic risk factors are associated with a higher risk of getting a TB infection. The risk of TB progressing from exposure, to infection, to active TB disease is largely determined by outside environmental factors. TB infection hinges on how infectious the source of the disease is, the closeness and length of your contact with an infected person, and social and behavioral factors (smoking, drinking, indoor air pollution, overcrowding, etc.).

Utilizing a healthcare-system-only approach will have limited success with environmental TB. Social and environmental interventions are not funded or delivered by health care systems. Public health workers must work with governments, non-governmental organizations and others to reduce poverty, improve housing, energy and education.

Schmidt, C.W. (Dec. 2008). Linking TB and the Environment: An Overlooked Mitigation Strategy. Environmental Health Perspectives, National Institute of Environmental Health Sciences. Retrieved 8-20-21, {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2592293/}

Srivastava, K., Kant, S., Verma, A. (Aug. 2015). Role of Environmental Factors in Transmission of Tuberculosis. Journal of Health. Retrieved 8-20-21, {https://journalofhealth.co.nz/wp-content/uploads/2015/12/DHH_Kant_TB.pdf}

Narasimhan, P., Wood, J., MacIntyre, C.R., Mathal, D. (2013). Risk Factors for Tuberculosis. Pulmonary Medicine. Retrieved 8-20-21, {https://www.hindawi.com/journals/pm/2013/828939/}

Epidemiology: Open Access. (2015). Environmental Risk Factors and Social Determinants of Pulmonary Tuberculosis in Pakistan. Retrieved 8-20-21, {https://www.omicsonline.org/open-access/environmental-risk-factors-and-social-determinants-of-pulmonary-tuberculosis-in-pakistan-2161-1165-1000201.php?aid=60783}

Lienhardt, C., Bennett, S., Del Prete, G., et. al. (June 2002). Investigation of Environmental and Host-related Risk Factors for Tuberculosis in Africa. American Journal of Epidemiology. Retrieved 8-20-21, {https://academic.oup.com/aje/article/155/11/1066/57338}

Medically reviewed by:

Dr. Javeed Siddiqui, MD, MPH

Dr. Siddiqui is the Chief Medical Officer at TeleMed2U responsible for clinical and technical program development as well as maintaining a thriving telemedicine practice in infectious diseases which includes specialized care of Hepatitis and HIV.

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Environmental Tuberculosis