Tuberculosis: Causes, symptoms, and treatments

Tuberculosis is an infectious disease that usually affects the lungs. Compared with other diseases caused by a single infectious agent, tuberculosis is the second biggest killer, globally.

In 2015, 1.8 million people died from the disease, with 10.4 million falling ill.

In the 18th and 19th centuries, a tuberculosis epidemic rampaged throughout Europe and North America, before the German microbiologist Robert Koch discovered the microbial causes of tuberculosis in 1882.

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.

However, in the mid-1980s, TB cases began to rise 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 labeled as such.

Fast facts on tuberculosis

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

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

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

What is tuberculosis?

Doctor looking at X-ray
TB usually affects the lungs, although it can spread to other organs around the body.

Doctors make a distinction between two kinds of tuberculosis infection: latent and active.

Latent TB – the bacteria remain in the body in an inactive state. They cause no symptoms and are not contagious, but they can become active.

Active TB – the bacteria do cause symptoms and can be transmitted to others.

About one-third of the world’s population is believed to have latent TB. There is a 10 percent chance of latent TB becoming active, 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.

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 percent of reported TB cases occurred in just 22 countries.

Early warning signs

According to the Centers for Disease Control and Prevention (CDC), the symptoms of TB disease include:

feeling sick or weak

loss of appetite and weight loss

chills, fever, and night sweats

a severe cough that lasts for 3 weeks or more

chest pain

TB can also affect other parts of the body. Symptoms will depend on the part it affects.


During a latent stage, TB has no symptoms. When TB is active TB, the cough, fever, and other symptoms can appear.

While TB usually affects the lungs, it can also affect other parts of the body, and the symptoms will vary accordingly.

Without treatment, TB can spread to other parts of the body through the bloodstream:

The bones: There may be spinal pain and joint destruction.

The brain: It can lead to meningitis.

The liver and kidneys: It can impair the waste filtration functions and lead to blood in the urine.

The heart: It can impair the heart’s ability to pump blood, resulting in cardiac tamponade, a condition that can be fatal.

Woman having injection
TB is most commonly diagnosed via a skin test involving an injection in the forearm.

To check for TB, a doctor will use a stethoscope to listen to the lungs and check for swelling in the lymph nodes. They will also ask about symptoms and medical history as well as assessing the individual’s risk of exposure to TB.

The most common diagnostic test for TB is a skin test where a small injection of PPD tuberculin, an extract of the TB bacterium, is made just below the inside forearm.

The injection site should be checked after 2-3 days, and, if a hard, red bump has swollen up to a specific size, then it is likely that TB is present.

Unfortunately, the skin test is not 100 percent accurate and has been known to give incorrect positive and negative readings.

However, there are other tests that are available to diagnose TB. Blood tests, chest X-rays, and sputum tests can all be used to test for the presence of TB bacteria and may be used alongside a skin test.

MDR-TB is more difficult to diagnose than regular TB. It is also difficult to diagnose regular TB in children.


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