Tuberculosis (TB) | Definition, Cause, Symptoms, & Treatment

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text-left"><em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www-britannica-com.translate.goog/science/tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB">tuberculosis</a> </div><button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0"> <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"> <li data-target="#ref1"> <div class="pl-25"> <a class="link-gray-900 w-100" href="https://www-britannica-com.translate.goog/science/tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB">Introduction</a> </div> <div class="ml-40 toc-drawer sub-toc-drawer"></div></li> <li data-target="#ref253296"> <div class="d-flex align-items-center"> <div class="ml-25"></div><a class="w-100 link-gray-900" href="https://www-britannica-com.translate.goog/science/tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB#ref253296">The course of tuberculosis</a> </div> <div class="ml-40 toc-drawer sub-toc-drawer"></div></li> <li data-target="#ref253297"> <div class="d-flex align-items-center"> <div class="ml-25"></div><a class="w-100 link-gray-900" href="https://www-britannica-com.translate.goog/science/tuberculosis/Diagnosis-and-treatment?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB">Diagnosis and treatment</a> </div> <div class="ml-40 toc-drawer sub-toc-drawer"></div></li> <li data-target="#ref253298"> <div class="d-flex align-items-center"> <div class="ml-25"></div><a class="w-100 link-gray-900" href="https://www-britannica-com.translate.goog/science/tuberculosis/Diagnosis-and-treatment?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB#ref253298">Other mycobacterial infections</a> </div> <div class="ml-40 toc-drawer sub-toc-drawer"></div></li> <li data-target="#ref253299"> <div class="d-flex align-items-center"> <div class="ml-25"></div><a class="w-100 link-gray-900" href="https://www-britannica-com.translate.goog/science/tuberculosis/Tuberculosis-through-history?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB">Tuberculosis through history</a> </div> <div class="ml-40 toc-drawer sub-toc-drawer"></div></li> </ul><a class="toc-extra-link link-gray-900" href="https://www-britannica-com.translate.goog/science/tuberculosis/additional-info?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="https://www-britannica-com.translate.goog/facts/tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB">Quick Facts & Related Topics</a> </div> 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href="https://www-britannica-com.translate.goog/science/scrofula?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" topicid="530041">scrofula</a> </dd> <dd> <a href="https://www-britannica-com.translate.goog/science/Pott-disease?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" topicid="472936">Pott disease</a> </dd> <dd> <a href="https://www-britannica-com.translate.goog/science/miliary-tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" topicid="382267">miliary tuberculosis</a> </dd> <dd> <a href="https://www-britannica-com.translate.goog/science/multidrug-resistant-tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" topicid="1208150">multidrug-resistant tuberculosis</a> </dd> <dd> <a href="https://www-britannica-com.translate.goog/science/totally-drug-resistant-tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" topicid="1840551">totally drug-resistant tuberculosis</a> </dd> </dl><button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"><a class="btn btn-sm btn-link p-0" href="https://www-britannica-com.translate.goog/facts/tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB"> See all related content </a> </div> </div> </div> </div> <div class="bg-gray-50 p-15 rounded module-spacing recent-news d-flex flex-column float-false"> <div> <h2 class="font-weight-bold font-14 m-0 d-inline">News <span class="text-gray-600">•</span></h2> <div class="recent-news-item first-recent-news-item d-inline"><a class="font-14 gtm-ap-news-link" href="https://translate.google.com/website?sl=auto&tl=en&hl=en-GB&u=https://www.news-medical.net/news/20241115/TB-pathogens-surprising-growth-mechanism-challenges-bacterial-biology.aspx" rel="nofollow">TB pathogen's surprising growth mechanism challenges bacterial biology</a> <span class="font-14 text-gray-600"> <span>•</span> Nov. 16, 2024, 12:27 AM ET (News-Medical) <button class="btn btn-link d-inline 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In most forms of the <a href="https://www-britannica-com.translate.goog/science/disease?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">disease</a>, the bacillus spreads slowly and widely in the <span id="ref279422"></span><a href="https://www-britannica-com.translate.goog/science/lung?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">lungs</a>, causing the formation of hard nodules (tubercles) or large cheeselike masses that break down the respiratory tissues and form cavities in the lungs. Blood <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="vessels" href="https://www-britannica-com.translate.goog/dictionary/vessels?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" data-type="EB">vessels</a> also can be eroded by the advancing disease, causing the infected person to <a href="https://www-britannica-com.translate.goog/science/cough?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">cough</a> up bright red blood.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span> <p class="topic-paragraph">During the 18th and 19th centuries, tuberculosis reached near-epidemic proportions in the rapidly urbanizing and industrializing societies of Europe and <a href="https://www-britannica-com.translate.goog/place/North-America?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">North America</a>. Indeed, “consumption,” as it was then known, was the leading cause of death for all age groups in the Western world from that period until the early 20th century, at which time improved <a href="https://www-britannica-com.translate.goog/topic/health?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">health</a> and hygiene brought about a steady decline in its mortality rates. Since the 1940s, <a href="https://www-britannica-com.translate.goog/science/antibiotic?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">antibiotic drugs</a> have reduced the span of treatment to months instead of years, and drug therapy has <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="done" href="https://www-britannica-com.translate.goog/dictionary/done?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" data-type="EB">done</a> away with the old TB sanatoriums where patients at one time were nursed for years while the defensive properties of their bodies dealt with the disease.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span> <p class="topic-paragraph">Today, in less-developed countries where population is dense and hygienic standards poor, tuberculosis remains a major fatal disease. The <a href="https://www-britannica-com.translate.goog/science/prevalence?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">prevalence</a> of the disease has increased in association with the HIV/<a href="https://www-britannica-com.translate.goog/science/AIDS?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">AIDS</a> epidemic; an estimated one out of every four deaths from tuberculosis involves an individual coinfected with <span id="ref1140363"></span><a href="https://www-britannica-com.translate.goog/science/HIV?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">HIV</a>. In addition, the successful elimination of tuberculosis as a major threat to <a href="https://www-britannica-com.translate.goog/topic/public-health?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">public health</a> in the world has been complicated by the rise of new strains of the tubercle bacillus that are <span id="ref895225"></span><a href="https://www-britannica-com.translate.goog/science/antibiotic-resistance?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">resistant</a> to conventional antibiotics. Infections with these strains are often difficult to treat and require the use of combination drug therapies, sometimes involving the use of five different agents.</p><span class="marker MOD3 mod-inline"></span> </section><span class="marker h2"></span> <section data-level="1" id="ref253296"> <h2 class="h1">The course of tuberculosis</h2><span class="marker PREMOD4 mod-inline"></span> <p class="topic-paragraph">The tubercle bacillus is a small, rod-shaped bacterium that is extremely hardy; it can survive for months in a state of dryness and can also resist the action of mild disinfectants. Infection spreads primarily by the <span id="ref279420"></span><a href="https://www-britannica-com.translate.goog/science/respiratory-disease?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">respiratory</a> route directly from an infected person who discharges live bacilli into the air. Minute droplets ejected by sneezing, coughing, and even talking can contain hundreds of tubercle bacilli that may be inhaled by a healthy person. There the bacilli become trapped in the tissues of the body, are surrounded by immune cells, and finally are sealed up in hard, nodular <span id="ref279424"></span><a href="https://www-britannica-com.translate.goog/science/tubercle-pathology?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink ">tubercles</a>. A tubercle usually consists of a centre of dead cells and tissues, cheeselike (caseous) in appearance, in which can be found many bacilli. This centre is surrounded by radially arranged phagocytic (scavenger) cells and a <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="periphery" href="https://translate.google.com/website?sl=auto&tl=en&hl=en-GB&u=https://www.merriam-webster.com/dictionary/periphery" data-type="MW">periphery</a> containing <a href="https://www-britannica-com.translate.goog/science/connective-tissue?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">connective tissue</a> cells. The tubercle thus forms as a result of the body’s defensive reaction to the bacilli. Individual tubercles are microscopic in size, but most of the visible <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="manifestations" href="https://translate.google.com/website?sl=auto&tl=en&hl=en-GB&u=https://www.merriam-webster.com/dictionary/manifestations" data-type="MW">manifestations</a> of tuberculosis, from barely visible nodules to large tuberculous masses, are conglomerations of tubercles.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span> <p class="topic-paragraph">In otherwise healthy <span id="ref180973"></span><a href="https://www-britannica-com.translate.goog/science/childhood-diseases-and-disorders?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">children</a> and adults, the primary infection often heals without causing symptoms. The bacilli are quickly sequestered in the tissues, and the infected person acquires a lifelong immunity to the disease. A <a href="https://www-britannica-com.translate.goog/science/skin-test?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">skin test</a> taken at any later time may reveal the earlier infection and the immunity, and a small scar in the <a href="https://www-britannica-com.translate.goog/science/lung?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">lung</a> may be visible by X-ray. In this condition, sometimes called <span id="ref1231147"></span>latent tuberculosis, the affected person is not <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="contagious" href="https://translate.google.com/website?sl=auto&tl=en&hl=en-GB&u=https://www.merriam-webster.com/dictionary/contagious" data-type="MW">contagious</a>. In some cases, however, sometimes after periods of time that can reach 40 years or more, the original tubercles break down, releasing viable bacilli into the bloodstream. From the blood the bacilli create new <a href="https://www-britannica-com.translate.goog/science/tissue?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">tissue</a> infections elsewhere in the body, most commonly in the upper portion of one or both lungs. This causes a condition known as <span id="ref895640"></span><a href="https://www-britannica-com.translate.goog/science/pulmonary-tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink ">pulmonary tuberculosis</a>, a highly infectious stage of the disease. In some cases the infection may break into the pleural space between the lung and the chest wall, causing a <a href="https://www-britannica-com.translate.goog/science/pleural-effusion?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">pleural effusion</a>, or collection of fluid outside the lung. Particularly among infants, the elderly, and immunocompromised adults (organ transplant recipients or AIDS patients, for example), the primary infection may spread through the body, causing <span id="ref895641"></span><a href="https://www-britannica-com.translate.goog/science/miliary-tuberculosis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink ">miliary tuberculosis</a>, a highly fatal form if not adequately treated. In fact, once the bacilli enter the bloodstream, they can travel to almost any organ of the body, including the <a href="https://www-britannica-com.translate.goog/science/lymph?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">lymph</a> nodes, bones and joints, skin, intestines, genital organs, kidneys, and bladder. An infection of the meninges that cover the brain causes <span id="ref180974"></span><a href="https://www-britannica-com.translate.goog/science/tuberculous-meningitis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink ">tuberculous meningitis</a>; before the advent of specific drugs, this disease was always fatal, though most affected people now recover.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="https://www-britannica-com.translate.goog/quiz/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg" alt="Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph." class="rounded-sm mr-15" width="70"> <div class="line-clamp clamp-5"> <div class="module-title bg-green"> Britannica Quiz </div> <div class="font-weight-semi-bold mt-5"> 44 Questions from Britannica’s Most Popular Health and Medicine Quizzes </div> </div></a> <div class="one-good-fact-module"> </div><span class="marker MOD5 mod-inline"></span> <span class="marker PREMOD6 mod-inline"></span> <p class="topic-paragraph">The onset of pulmonary tuberculosis is usually <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="insidious" href="https://translate.google.com/website?sl=auto&tl=en&hl=en-GB&u=https://www.merriam-webster.com/dictionary/insidious" data-type="MW">insidious</a>, with lack of energy, weight loss, and persistent cough. These symptoms do not subside, and the general health of the patient deteriorates. Eventually, the cough increases, the patient may have chest pain from <a href="https://www-britannica-com.translate.goog/science/pleurisy?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">pleurisy</a>, and there may be blood in the sputum, an alarming symptom. Fever develops, usually with drenching night sweats. In the lung, the <span id="ref279423"></span><a href="https://www-britannica-com.translate.goog/science/lesion?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink " data-show-preview="true">lesion</a> consists of a collection of dead cells in which tubercle bacilli may be seen. This lesion may erode a neighbouring bronchus or <a href="https://www-britannica-com.translate.goog/science/blood-vessel?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">blood vessel</a>, causing the patient to cough up blood (<span id="ref180975"></span><a href="https://www-britannica-com.translate.goog/science/hemoptysis?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink ">hemoptysis</a>). Tubercular <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="lesions" href="https://www-britannica-com.translate.goog/dictionary/lesions?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" data-type="EB">lesions</a> may spread extensively in the lung, causing large areas of destruction, cavities, and scarring. The amount of lung tissue available for the exchange of gases in respiration decreases, and if untreated the patient will die from failure of ventilation and general toxemia and <a href="https://www-britannica-com.translate.goog/science/fatigue-physiology?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-GB" class="md-crosslink autoxref " data-show-preview="true">exhaustion</a>.</p><span class="marker MOD6 mod-inline"></span> </section><span class="marker end-of-content"></span><span class="marker after-article"></span> </div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article> </div> </div> </div> </div> </main> <div id="md-footer"></div> <noscript> <iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe> </noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script> <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":3,"pageId":608235,"pageLength":933,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"D","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> <script defer src="https://static.cloudflareinsights.com/beacon.min.js/vcd15cbe7772f49c399c6a5babf22c1241717689176015" integrity="sha512-ZpsOmlRQV6y907TI0dKBHq9Md29nnaEIPlkf84rnaERnq6zvWvPUqr2ft8M1aS28oN72PdrCzSjY4U6VaAw1EQ==" data-cf-beacon="{"rayId":"8e88b03dc8964d33","version":"2024.10.5","serverTiming":{"name":{"cfExtPri":true,"cfL4":true,"cfSpeedBrain":true,"cfCacheStatus":true}},"token":"5cc7d7124de641b181da990fc8c9a0b6","b":1}" crossorigin="anonymous"></script> <script>function gtElInit() {var lib = new google.translate.TranslateService();lib.translatePage('en', 'en', function () {});}</script> <script src="https://translate.google.com/translate_a/element.js?cb=gtElInit&hl=en-GB&client=wt" type="text/javascript"></script> </body> </html>

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Tuberculosis (TB) | Definition, Cause, Symptoms, & Treatment | Britannica