Tuberculosis

Tuberculosis

Symptoms and Causative Agent

Tuberculosis is a disease caused by the tuberculosis bacteria, Mycobacterium tuberculosis.

Symptoms of active tuberculosis infection include cough lasting several weeks, coughing up sputum (mucus) or blood, fever, night sweats, fever, and pain in the chest.

Some people may be infected with tuberculosis bacteria but have no symptoms. This is called latent tuberculosis. Latent tuberculosis may lead to active disease. Some people with latent tuberculosis may never become ill.

Transmission

The tuberculosis bacteria are spread via infected respiratory droplets, such as those that are spread when ill people cough or sneeze, or even speak. An uninfected person may inhale infected droplets into her or his lungs and become infected.

People with latent tuberculosis infections do not spread tuberculosis bacteria to others around them.

Treatment and Care

Most cases of tuberculosis can be successfully treated. People with active tuberculosis disease are treated with antibiotics and other drugs that kill or control the tuberculosis bacteria. Treatment usually lasts several months.

People with latent tuberculosis can be treated with antibiotics to ensure that they do not later become ill with active tuberculosis.

In recent years, some tuberculosis strains have become resistant to antibiotics. These cases are more difficult and expensive to treat, and treatment can have serious side effects. Because drug-resistant tuberculosis is extremely challenging to treat, preventing the condition is important. Prevention measures include ensuring that people who have tuberculosis take all of the medication prescribed to them and that they are treated with the correct medication.

Complications and Mortality

Though the route of tuberculosis infection is respiratory, and the main symptoms are usually respiratory, tuberculosis bacteria can spread to and infect other parts of the body, such as the bones and brain.

Untreated active tuberculosis disease can be fatal. About 3% of people with untreated TB will die. This figure is much higher, however, when a person also has human immunodeficiency virus (HIV) infection. About 18% of people with active TB infection and HIV infection may die.

Active TB infection is more deadly for very young children, too. They are more likely to have serious complications from TB such as TB meningitis (infection of the lining surround the brain).

In 2014, 9.6 million people became ill with tuberculosis. About 1.5 million people, including about 140,000 children, died from tuberculosis. About one-third of the world’s population has latent tuberculosis.

Available Vaccines and Vaccination Campaigns

The bacille Calmette–Guérin (BCG) vaccine is used as part of national vaccination programs in countries with many cases of TB. The vaccine does not protect children from pulmonary disease caused by TB bacteria, nor does it prevent latent TB infection from progressing to active disease. It does, however, prevent some serious TB complications in children, such as TB meningitis. The vaccine is generally not used in adults, and the vaccine in children does not prevent spread of the disease.

The BCG vaccine has been in use since 1921. Many researchers are working to develop a more effective tuberculosis vaccine. The hope is to develop a vaccine that prevents infection with tuberculosis, which would reduce the great burden of disease global and also reduce transmission of the TB bacteria.

Vaccination Recommendations

In countries with many cases of TB, the BCG vaccine is given to infants shortly after they are born. Infants with HIV infection are not recommended to get the vaccine.

In countries with very few cases of TB, infants may be recommended to take the vaccine if they are likely to be exposed to TB, such as by living in a home with an adult with active TB infection.


Sources

Centers for Disease Control and Prevention. Basic TB facts. Accessed 2/24/2016.

Straetemans M, Glaziou P, Bierrenbach AL, Sismanidis C, & van der Werf MJ. Assessing tuberculosis case fatality ratio: a meta-analysis. PLoS One, 2011;6(6), e20755.

World Health Organization. Childhood tuberculosis. Accessed 2/24/2016.

World Health Organization. Position paper on BCG vaccine. Accessed 2/24/2016.

World Health Organization. Revised BCG vaccination guidelines for infants at risk for HIV infection. Accessed 2/24/2016.

World Health Organization. Tuberculosis fact sheet. Accessed 2/24/2016.

World Health Organization. Tuberculosis vaccine development. Accessed 2/24/2016.

Last update 24 Feb 2016

Timeline Entry: 3/24/1882

Tuberculosis: Koch Isolates and Cultures Bacillii

Robert Koch (1843-1910) announced his discovery of the agent that causes tuberculosis. For a time, it was called Koch’s bacillus. Today it is called Mycobacterium tuberculosis.

Tuberculosis was a widespread, deadly disease in the 1800s. As Koch said when he presented his findings,

“One in seven of all human beings dies from tuberculosis. If one only considers the productive middle-age groups, tuberculosis carries away one-third, and often more.”

Koch began to work on a vaccine for treatment and prevention of tuberculosis.

In 1905 Koch would win the Nobel Prize in Physiology or Medicine "for his investigations and discoveries in relation to tuberculosis."

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Timeline Entry: 2016

Tuberculosis: BCG Today

BCG vaccination for tuberculosis has never been recommended for routine use in the United States. It is, however, frequently used for children in countries where risk of TB infection is high.

Three tuberculosis vaccines are currently licensed in the United States. The Advisory Council on Immunization Practices recommends them only for children and certain health care workers who have a high risk of infection with TB (because of ongoing or frequent exposure to TB).

Reports of the effectiveness of BCG for tuberculosis immunization vary greatly, though efficacy seems to be best in younger people. It is widely used in countries where the disease burden of TB is high. The World Health Organization states,

“[BCG is] is one of the most widely used of all current vaccines, reaching >80%of neonates and infants in countries where it is part of the national childhood immunization programme. BCG vaccine has a documented protective effect against meningitis and disseminated TB in children. It does not prevent primary infection and, more importantly, does not prevent reactivation of latent pulmonary infection, the principal source of bacillary spread in the community. The impact of BCG vaccination on transmission of [tuberculosis] is therefore limited.“ —WHO, BCG Vaccine

WHO estimates that one third of the world’s population is infected with the tuberculosis bacillus. In 2014, 9.6 million people became ill with tuberculosis. About 1.5 million people, including about 140,000 children, died from tuberculosis. Drug-resistant tuberculosis is becoming an increasing problem.

Researchers continue to try to develop new, more reliable and effective tuberculosis vaccines. Areas gaining a great deal of research attention are DNA vaccines and subunit TB vaccines.

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