Tuberculosis: Causes, Symptoms and Treatments - Medical

Tuberculosis has a long, rich history, dating back as far as Ancient Egypt, with evidence of its presence found in the preserved spines of Egyptian mummies.¹

In the 18th and 19th centuries, a tuberculosis epidemic rampaged throughout Europe and North America,² before the German microbiologist Robert Koch discovered the microbial causes of tuberculosis in 1882.³

Following Koch's discovery, the development of vaccines and effective drug treatment led to the belief that the disease was almost defeated. Indeed, at one point the United Nations, predicted that tuberculosis (TB) would be eliminated worldwide by 2025.³

However, in the mid-80s, TB cases began to rise once more in the US and worldwide, so much so that in 1993 the World Health Organization (WHO) declared that TB was a global emergency; the first time that a disease had been labelled as such.⁴

Fortunately, with proper treatment almost all cases of tuberculosis are curable. Cases of TB have decreased in the US since 1993, but the disease remains a concern. Without proper treatment up to two-thirds of people ill with tuberculosis will die.⁵

You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also, look out for links to information about related conditions.

Fast facts on tuberculosis

Here are some key points about tuberculosis. More detail and supporting information is in the main article.

• In 2012, 1.3 million people were believed to have died because of tuberculosis with an estimated 8.6 million new cases of TB worldwide.¹³
• The World Health Organization estimates that 9 million people a year get sick with TB, with 3 million of these "missed" by health systems.
• TB is among the top 3 causes of death for women aged 15 to 44.
• Tuberculosis is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs, although it can also affect other organs such as the kidneys and heart.⁵
• TB can either be active or latent (where no symptoms occur, and the condition cannot be passed on).
• TB symptoms (cough, fever, night sweats, weight loss etc.) may be mild for many months, and people ill with TB can infect up to 10-15 other people through close contact over the course of a year.
• TB is an airborne pathogen, meaning that the bacteria that cause TB can spread through the air from person to person.
• People with compromised immune systems are most at risk of developing active TB and dying from the disease; people with HIV are 26-31 times more likely to develop TB.
• Tobacco use has been found to increase the risk of developing active TB with more than 20% of TB cases worldwide attributable to smoking.
• TB bacteria can develop a resistance to antibiotics that fail to kill them completely.
• The most common diagnostic test for tuberculosis is a skin test.
• The majority of TB cases can be cured with antibiotic treatment, with isoniazid and rifampicin the two most powerful, first-line (or standard) anti-TB drugs. TB bacteria can develop a resistance to antibiotics that fail to kill them completely.
• It is vital that any courses of treatment given are fully completed to increase the chance of successful eradication of infection and to reduce the risk of antibiotic resistance developing.

What is tuberculosis?

TB is an infectious disease that usually affects the lungs. It is the second greatest killer due to a single infectious agent worldwide, and in 2012, 1.3 million people died from the disease, with 8.6 million falling ill.⁵

Doctors make a distinction between two kinds of tuberculosis infection: latent and active. In latent TB, the TB bacteria remain in the body in an inactive state. They cause no symptoms and are not contagious, but they can become active. In active TB, the bacteria do cause symptoms and can be transmitted to others.⁶

About one-third of the world's population is believed to have latent TB. There is a 10% chance of latent TB becoming active TB, but this risk is much higher in people who have compromised immune systems i.e. people living with HIV or malnutrition, or people who smoke.⁵

TB affects all age groups and all parts of the world. However, the disease mostly affects young adults, and people living in developing countries. In 2012, 80% of reported TB cases occurred in just 22 countries.⁵

What causes tuberculosis?⁵⁷⁸

The Mycobacterium tuberculosis bacterium causes TB. It is spread through the air when a person with TB (whose lungs are affected) coughs, sneezes, spits, laughs or talks.

TB is contagious, but it is not easy to catch. The chances of catching TB from someone you live or work with are much higher than from a stranger. Most people with active TB who have received appropriate treatment for at least two weeks are no longer contagious.

Since antibiotics began to be used to fight TB, some strains have become resistant to drugs. Multidrug-resistant TB (MDR-TB) arises when an antibiotic fails to kill all of the bacteria that it targets, with the surviving bacteria developing resistance to that antibiotic and often others at the same time.

MDR-TB is treatable and curable only with the use of very specific anti-TB drugs, which are often limited or not readily available. In 2012, around 450,000 people developed MDR-TB.

Who is at risk?

People with compromised immune systems are most at risk of developing active tuberculosis.

HIV suppresses the immune system, making it harder for the body to control TB bacteria. People who are infected with both HIV and TB are around 20-30% more likely to develop active TB than those who do not have HIV.

Tobacco use has also been found to increase the risk of developing active TB. Over 20% of TB cases worldwide are related to smoking.⁵

Recent developments on tuberculosis causes from MNT news

Alarming spread of drug-resistant TB threatens global health

The medical aid organization Medecins Sans Frontieres/Doctors Without Borders (MSF) has published a briefing paper about the alarming spread of drug-resistant tuberculosis, which they refer to as the "biggest threat to global health you've never heard of."

Patients with untreatable tuberculosis 'are spreading infection'

A new study published in The Lancet has found that patients in South Africa with untreatable tuberculosis are being discharged into the community, which, according to researchers, is contributing to the spread of the disease.

Study helps explain how a parasitic worm increases TB risk

Studies have shown that infection with helminths - a form of parasitic worm - can increase susceptibility to tuberculosis in those with a latent form of the disease. Now, new research sheds light on why this is, opening the door to new strategies to prevent the disease.

Symptoms of tuberculosis⁶⁷⁹

While latent TB is symptomless, the symptoms of active TB include the following:

• Coughing, sometimes with mucus or blood
• Chills
• Fatigue
• Fever
• Loss of weight
• Loss of appetite
• Night sweats.

Tuberculosis usually affects the lungs, but can also affect other parts of the body. When TB occurs outside of the lungs, the symptoms can vary accordingly. Without treatment, TB can spread to other parts of the body through the bloodstream:

• TB infecting the bones can lead to spinal pain and joint destruction
• TB infecting the brain can cause meningitis
• TB infecting the liver and kidneys can impair their waste filtration functions and lead to blood in the urine
• TB infecting the heart can impair the heart's ability to pump blood, resulting in a condition called cardiac tamponade that can be fatal.

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On the next page we look at tests to diagnose tuberculosis, how it can be prevented and the available treatment options for tuberculosis.

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