Tuberculosis

"TB" redirects here. For the unit of information, see Terabyte.

Tuberculosis (TB) is an infectious disease caused by bacteria. In the past, people called it consumption or the white death.

Tuberculosis
Classification and external resources
Chest X-ray of a person with advanced tuberculosis. White arrows point to infection in both lungs. Black arrows point to a cavity that has formed.
ICD-10	A15.–A19.
ICD-9	010–018
OMIM	607948
DiseasesDB	8515
MedlinePlus	000077
eMedicine	med/2324
MeSH	D014376

TB is caused by several types of mycobacteria, usually Mycobacterium tuberculosis.^[1] The disease usually attacks the lungs, but it can also affect other parts of the body.

How it spreads

The bacteria can travel through the air and spread from one person to the next. This happens when infected people cough, sneeze, or spit.^[2]

Of every 100 people with TB, between five and ten people show symptoms.^[3] In these people, the disease is called active. Tuberculosis kills more than half of the people who are infected if they do not get treatment. TB affects a lot of people globally, but many do not show any symptoms.^[4]

This world map shows the prevalence of TB, per 100,000 people, as of 2016. Countries with more cases are shown in darker colors, those with fewer cases are shown in lighter colors. The most cases were recorded in Southeast Asia and Sub-Saharan Africa.^[5]

Detection and treatment

Diagnosis of active TB relies on radiology. Doctors often look at an X-ray of the chest. In addition, they check body fluids. These fluids have microbes in them, which are grown in a cell culture. The cell cultures are then analysed to see if the person is infected with TB.

If the patient has TB, but does not show symptoms, the disease is 'latent'. Doctors use a skin test, called the Mantoux test, to detect latent TB. They often do blood tests too.

Synovial fluid examination^[6][7]

Type	WBC (per mm3)	% neutrophils	Viscosity	Appearance
Normal	<200	0	High	Transparent
Osteoarthritis	<5000	<25	High	Clear yellow
Trauma	<10,000	<50	Variable	Bloody
Inflammatory	2,000–50,000	50–80	Low	Cloudy yellow
Septic arthritis	>50,000	>75	Low	Cloudy yellow
Gonorrhea	~10,000	60	Low	Cloudy yellow
Tuberculosis	~20,000	70	Low	Cloudy yellow
Inflammatory: Arthritis, gout, rheumatoid arthritis, rheumatic fever

There is a vaccine against some forms of tuberculosis. It is called the Bacillus Calmette–Guérin vaccine.^{[verification needed]}

TB used to be easily treated and cured with antibiotics. However, the bacterium is now highly resistant to most antibiotics. This resistance makes treatment difficult. Many different kinds of antibiotics need to be given over a long period of time. There is a form of tuberculosis that is resistant to all drugs.

Symptoms

Tuberculosis can have many symptoms.

The most common include:

• A cough that does not go away, especially if the person is coughing up blood (this is called hemoptysis)
• Chest pain
• Not having any appetite
• Weakness
• Weight loss
• Chills
• Very pale skin
• Listless eyes
• Fever
• Sweating a lot at night
• Difficulty breathing
• Feeling very tired
• People are also more likely to get tuberculosis if they live close to other people who have TB. For example, TB can spread easily in homeless shelters, prisons, and immigrant communities

  

  Public health campaigns in the 1920s tried to halt the spread of TB.

How common is TB?

Experts believe that one third of the world population is infected with M. tuberculosis.^[4]

New infections occur at a rate of one per second.^[4] In 2007, about 13.7 million chronic cases were active globally.^[8] In 2010, about 8.8 million new cases developed and nearly 1.5 million people died from the disease, most of them in developing countries.^[9] The number of tuberculosis cases has been decreasing since 2006, and new cases have decreased since 2002.^[9]

Tuberculosis does not happen at the same rate around the world. About eighty percent of the population in many Asian and African countries test positive for TB, but only five to ten percent of people in the United States do.^[1]

People usually get tuberculosis because of a weakened immune system. Many people with HIV and AIDS can also get tuberculosis because it causes the person to become immunocompromised.^[10]