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Dynamics of tuberculosis infection in Sweden

Winqvist, Niclas LU (2011) In Lund University, Faculty of Medicine Doctoral Dissertation Series 2011:54.
Abstract (Swedish)
Popular Abstract in Swedish

Det finns två skäl till att Sverige lämpar sig särskilt väl för att studera tuberkulosepidemiologi: 1) den svenska tuberkulosepidemiologin har gått från en svår epidemi i slutet av 1800-talet, fullt i paritet med de värst drabbade länderna globalt idag, till den situation vi har idag nästan helt utan inhemsk smittspridning. 2) En allt större del av befolkningen som växte upp och smittades under 1920 och 30-talen når hög ålder och riskerar att aktivera en latent tuberkulosinfektion genom sjukdomar eller medicinska behandlingar som försvagar immunförsvaret. Man kunde därför förvänta sig att allt fler i de högsta åldersgrupperna skulle aktivera en gammal tuberkulosinfektion och insjukna i aktiv... (More)
Popular Abstract in Swedish

Det finns två skäl till att Sverige lämpar sig särskilt väl för att studera tuberkulosepidemiologi: 1) den svenska tuberkulosepidemiologin har gått från en svår epidemi i slutet av 1800-talet, fullt i paritet med de värst drabbade länderna globalt idag, till den situation vi har idag nästan helt utan inhemsk smittspridning. 2) En allt större del av befolkningen som växte upp och smittades under 1920 och 30-talen når hög ålder och riskerar att aktivera en latent tuberkulosinfektion genom sjukdomar eller medicinska behandlingar som försvagar immunförsvaret. Man kunde därför förvänta sig att allt fler i de högsta åldersgrupperna skulle aktivera en gammal tuberkulosinfektion och insjukna i aktiv tuberkulos. Så är det emellertid inte utan tuberkulossjukdom minskar även i dessa åldersgrupper vilket skulle kunna tyda på en hög grad av spontan utläkning av tuberkulosinfektion över tid. Denna avhandling visar att cirka 10 % av de som smittas med tuberkulos också insjuknar men gör det inom de första åren efter smittillfället. Sedan smittöverföringen av tuberkulos i det närmaste upphörde i slutet av 1960-talet insjuknar endast 2 % av de som smittas. Utifrån underlaget i vår studie läker smittade individer ut sin tuberkulosinfektion i en takt av 4,5 % årligen.

Sedan tuberkulosepidemin nästan helt avstannade under andra halvan av 1900-talet är det i allt större utsträckning den utlandsfödda befolkningen som insjuknar efter att ha blivit smittade i sina respektive hemländer. Vi har kunnat visa att risken att insjukna sjunker snabbt efter ankomst till Sverige.

Vi har också utvärderat nyttan av ett nytt, immunologiskt test för latent tuberkulosinfektion vid fall av misstänkt aktiv tuberkulos. Detta så kallade Quantiferontest fungerade dåligt vid lungtuberkulos, den vanligaste formen av tuberkulos, men skulle kunna tillföra viss hjälp som komplement vid undersökning av misstänkt lymfkörteltuberkulos. (Less)
Abstract
Sweden provides a special setting for epidemiological and demographic studies of tuberculosis (TB) infection over time for principally two reasons; first, the Swedish TB epidemic has undergone a tremendous transition since the end of the 19th century, when TB was highly endemic, to the current situation with practically interrupted indigenous transmission since several decades. Second, an increasing proportion of persons who grew up before TB transmission virtually disappeared in the 1960s are reaching advanced age, and thus creating conditions that predispose to reactivation of latent TB infection (LTBI). Since it can be assumed that most subjects in these cohorts have LTBI, increasing rates of reactivation TB would be expected if they... (More)
Sweden provides a special setting for epidemiological and demographic studies of tuberculosis (TB) infection over time for principally two reasons; first, the Swedish TB epidemic has undergone a tremendous transition since the end of the 19th century, when TB was highly endemic, to the current situation with practically interrupted indigenous transmission since several decades. Second, an increasing proportion of persons who grew up before TB transmission virtually disappeared in the 1960s are reaching advanced age, and thus creating conditions that predispose to reactivation of latent TB infection (LTBI). Since it can be assumed that most subjects in these cohorts have LTBI, increasing rates of reactivation TB would be expected if they actually harbored viable TB bacilli. However, case rates in the indigenous Swedish population continue to decline suggesting that spontaneous clearance of LTBI occurs over time. Hence, data from Sweden can provide new insights into the natural course of LTBI. This thesis shows that about 10% of infected individuals ever develop active TB but the majority does so within the first years from infection. When transmission is halted in the society only about 2% reactivate LTBI. In our setting clearance of M. tuberculosis was shown to occur at an annual rate of 4.5% when following subjects with known year of infection.

The demographic pattern of TB in Sweden has turned to a disease principally affecting the immigrant population. Recent immigration from countries with high TB incidence constitutes the highest risk as shown by a fourfold higher risk for active TB among immigrants from the Horn of Africa in East Denmark compared to immigrants from the same area with residence in Scania, Sweden.

The use of an interferon-gamma release assay for identifying active TB was unsatisfactory, especially in cases of pulmonary disease, and thus the usefulness of the assay for this purpose is questionable. The test performed better in patients with suspected lymph node TB, and hence it might be considered for inclusion in the diagnostic protocol in that context. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Giesecke, Johan, European Centre for Disease Prevention and Contol
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Tuberculosis, latent tuberculosis infection, long-term follow-up, Øresund region, interferon-gamma release assay, tuberculin skin test
in
Lund University, Faculty of Medicine Doctoral Dissertation Series
volume
2011:54
pages
155 pages
publisher
Lund University
defense location
Medicinens aula, ing 35, SUS Malmö
defense date
2011-05-31 13:00
ISSN
1652-8220
ISBN
978-91-86871-03-1
language
English
LU publication?
yes
id
66e2f33b-07e3-467c-945f-be02c077b7ec (old id 1940355)
date added to LUP
2011-05-11 08:47:10
date last changed
2016-09-19 08:44:49
@phdthesis{66e2f33b-07e3-467c-945f-be02c077b7ec,
  abstract     = {Sweden provides a special setting for epidemiological and demographic studies of tuberculosis (TB) infection over time for principally two reasons; first, the Swedish TB epidemic has undergone a tremendous transition since the end of the 19th century, when TB was highly endemic, to the current situation with practically interrupted indigenous transmission since several decades. Second, an increasing proportion of persons who grew up before TB transmission virtually disappeared in the 1960s are reaching advanced age, and thus creating conditions that predispose to reactivation of latent TB infection (LTBI). Since it can be assumed that most subjects in these cohorts have LTBI, increasing rates of reactivation TB would be expected if they actually harbored viable TB bacilli. However, case rates in the indigenous Swedish population continue to decline suggesting that spontaneous clearance of LTBI occurs over time. Hence, data from Sweden can provide new insights into the natural course of LTBI. This thesis shows that about 10% of infected individuals ever develop active TB but the majority does so within the first years from infection. When transmission is halted in the society only about 2% reactivate LTBI. In our setting clearance of M. tuberculosis was shown to occur at an annual rate of 4.5% when following subjects with known year of infection. <br/><br>
The demographic pattern of TB in Sweden has turned to a disease principally affecting the immigrant population. Recent immigration from countries with high TB incidence constitutes the highest risk as shown by a fourfold higher risk for active TB among immigrants from the Horn of Africa in East Denmark compared to immigrants from the same area with residence in Scania, Sweden.<br/><br>
The use of an interferon-gamma release assay for identifying active TB was unsatisfactory, especially in cases of pulmonary disease, and thus the usefulness of the assay for this purpose is questionable. The test performed better in patients with suspected lymph node TB, and hence it might be considered for inclusion in the diagnostic protocol in that context.},
  author       = {Winqvist, Niclas},
  isbn         = {978-91-86871-03-1},
  issn         = {1652-8220},
  keyword      = {Tuberculosis,latent tuberculosis infection,long-term follow-up,Øresund region,interferon-gamma release assay,tuberculin skin test},
  language     = {eng},
  pages        = {155},
  publisher    = {Lund University},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series},
  title        = {Dynamics of tuberculosis infection in Sweden},
  volume       = {2011:54},
  year         = {2011},
}