Tuberculosis

== Prognosis ==

[[File:Tuberculosis world map - DALY - WHO2004.svg|thumb|upright=1.4|[[Age adjustment|Age-standardized]] [[disability-adjusted life year]]s caused by tuberculosis per 100,000&nbsp;inhabitants in 2004.<ref>{{cite web |url=https://www.who.int/healthinfo/global_burden_disease/estimates_country/en/index.html |title=WHO Disease and injury country estimates |year=2004 |publisher=World Health Organization (WHO) |access-date=11 November 2009 |url-status=live |archive-url=https://web.archive.org/web/20091111101009/http://www.who.int/healthinfo/global_burden_disease/estimates_country/en/index.html |archive-date=11 November 2009 }}</ref>
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Progression from TB infection to overt TB disease occurs when the bacilli overcome the immune system defenses and begin to multiply. In primary TB disease (some 1–5% of cases), this occurs soon after the initial infection.<ref name=Robbins/> However, in the majority of cases, a [[Latent tuberculosis|latent infection]] occurs with no obvious symptoms.<ref name=Robbins/> These dormant bacilli produce active tuberculosis in 5–10% of these latent cases, often many years after infection.<ref name=Pet2005/>

The risk of reactivation increases with [[immunosuppression]], such as that caused by infection with HIV. In people coinfected with ''M. tuberculosis'' and HIV, the risk of reactivation increases to 10% per year.<ref name=Robbins/> Studies using [[DNA fingerprinting]] of ''M. tuberculosis'' strains have shown reinfection contributes more substantially to recurrent TB than previously thought,<ref>{{cite journal | vauthors = Lambert ML, Hasker E, Van Deun A, Roberfroid D, Boelaert M, Van der Stuyft P | title = Recurrence in tuberculosis: relapse or reinfection? | journal = The Lancet. Infectious Diseases | volume = 3 | issue = 5 | pages = 282–7 | date = May 2003 | pmid = 12726976 | doi = 10.1016/S1473-3099(03)00607-8 }}</ref> with estimates that it might account for more than 50% of reactivated cases in areas where TB is common.<ref>{{cite journal | vauthors = Wang JY, Lee LN, Lai HC, Hsu HL, Liaw YS, Hsueh PR, Yang PC | title = Prediction of the tuberculosis reinfection proportion from the local incidence | journal = The Journal of Infectious Diseases | volume = 196 | issue = 2 | pages = 281–8 | date = July 2007 | pmid = 17570116 | doi = 10.1086/518898 | doi-access = free }}</ref> The chance of death from a case of tuberculosis is about 4% {{as of|2008|lc=yes}}, down from 8% in 1995.<ref name=Lancet11/>

In people with smear-positive pulmonary TB (without HIV co-infection), after 5 years without treatment, 50-60% die while 20-25% achieve spontaneous resolution (cure). TB is almost always fatal in those with untreated HIV co-infection and death rates are increased even with antiretroviral treatment of HIV.<ref>{{Cite web|title=1.4 Prognosis - Tuberculosis|url=https://medicalguidelines.msf.org/viewport/TUB/latest/1-4-prognosis-20320185.html|access-date=25 August 2020|website=medicalguidelines.msf.org|archive-date=2 June 2021|archive-url=https://web.archive.org/web/20210602215007/https://medicalguidelines.msf.org/viewport/TUB/latest/1-4-prognosis-20320185.html|url-status=live}}</ref>
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