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Epidemiological aspects of tuberculosis in Guinea-Bissau, West Africa

Gustafson, Per LU (2003)
Abstract (Swedish)
Popular Abstract in Swedish

Tuberkulos (Tbc) är en sjukdom som plågat mänskligheten sedan årtusenden före Kristi födelse. Bakterien som orsakar Tbc sprids från person till person företrädesvis via luftvägarna. En tredjedel av världens befolkning tros vara smittad; ca 10% av dessa utvecklar aktiv Tbc någon gång under livet. Totalt insjuknar årligen ca 8 miljoner personer i Tbc; 2 miljoner av dem dör av sjukdomen. Förutom studier av kopplingen mellan Tbc och HIV/AIDS så är sjukdomens epidemiologi i utvecklingsländer dåligt klarlagd. Syftet med denna avhandling har varit att belysa riskfaktorer för positiv tuberkulinreaktion, alltså det test som används för att påvisa infektion, i den allmänna befolkningen och bland... (More)
Popular Abstract in Swedish

Tuberkulos (Tbc) är en sjukdom som plågat mänskligheten sedan årtusenden före Kristi födelse. Bakterien som orsakar Tbc sprids från person till person företrädesvis via luftvägarna. En tredjedel av världens befolkning tros vara smittad; ca 10% av dessa utvecklar aktiv Tbc någon gång under livet. Totalt insjuknar årligen ca 8 miljoner personer i Tbc; 2 miljoner av dem dör av sjukdomen. Förutom studier av kopplingen mellan Tbc och HIV/AIDS så är sjukdomens epidemiologi i utvecklingsländer dåligt klarlagd. Syftet med denna avhandling har varit att belysa riskfaktorer för positiv tuberkulinreaktion, alltså det test som används för att påvisa infektion, i den allmänna befolkningen och bland Tbc-fallens familjemedlemmar, samt riskfaktorer för aktiv sjukdom och död i Tbc.



Fyra bostadsområden (43,000 invånare) i Bissau, huvudstaden i Guinea-Bissau, har följts genom ett befolkningsregister sedan mer än 25 år. 1996 startades ett övervakningssystem för Tbc i området; alla vuxna (>15 år) med aktiv Tbc i lungor/bröstkorg inkluderades och undersöktes. Data från befolkningsregistret tillät jämförelser av dessa Tbc-patienter med hela den övriga befolkningen i området avseende frekvens av sjukdomen samt riskfaktorer.



Mellan 1996 och 2001 inkluderades totalt 811 Tbc-patienter. Risken för positiv tuberkulinreaktion var starkt associerad till tidigare eller nylig exposition för Tbc. Omfattningen och närheten av kontakten med Tbc-fallet var av stor betydelse för familjemedlemmarnas risk för positiv reaktion. BCG-vaccination hade föga inflytande på tolkningen av tuberkulintestet. Ett tuberkulintest utfört under den tidiga regnperioden, från Juni till Augusti, ledde till mindre reaktioner än under övriga tider på året och testning under dessa månader kan leda till feltolkning av resultaten. Incidensen av aktiv Tbc i området var hög; 471/100,000 i den vuxna befolkningen. Både HIV-1 och HIV-2 ökade kraftigt risken för Tbc; effekten var dock betydligt högre för HIV-1. Andra faktorer associerade med ökad risk för Tbc korrelerade väl med de faktorer som antogs vara viktiga i Europa och USA under 1800- och 1900-talets början: män hade högre risk än kvinnor, ökad ålder, fattigdom, dålig utbildningsnivå och många vuxna som bor tillsammans. Ett intressant fynd var att barn föreföll ha en skyddande effekt; barn i ett hushåll minskade risken för Tbc bland vuxna. Dödligheten bland Tbc-patienterna ökade om de samtidigt var infekterade med HIV-1, men även HIV-2 gav en ökad risk för död. Symptom och tecken till dåligt immunförsvar, t.ex. svampinfektioner i munnen, eller undernäring ökade risken för död bland både HIV-positiva och HIV-negativa Tbc-patienter. Mätning av ”mid-upper-arm circumference”, dvs. uppskattning av överarmens omfång, var ett bra hjälpmedel för att bedöma nutritionsstatus och var väl korrelerat till en ökad risk för död. Ett inbördeskrig 1998-1999 ledde till att patienterna tog sin medicinering oregelbundet, vilket orsakade en 3-faldig ökning av dödligheten. Ökningen sågs framför allt bland HIV-positiva patienter, och denna ökade dödlighet kvarstod även efter kriget. (Less)
Abstract
Tuberculosis (TB) has plagued the humanity for several thousands of years. The bacteria causing TB is mainly spread from person to person as an aerosol transmission. It is estimated that one third of the world’s population is infected with the disease; about 10% of these will develop active TB during their lifetime. In year 2000, 8 million TB-cases were detected, of which 2 million died. Except for studies of the correlation between TB and HIV/AIDS, the epidemiology of TB in developing countries has been little investigated. The aims of this thesis have been to evaluate risk factors for positive tuberculin skin test (TST), which is the test for diagnosing TB infection, in the population and among TB-case household members, to assess... (More)
Tuberculosis (TB) has plagued the humanity for several thousands of years. The bacteria causing TB is mainly spread from person to person as an aerosol transmission. It is estimated that one third of the world’s population is infected with the disease; about 10% of these will develop active TB during their lifetime. In year 2000, 8 million TB-cases were detected, of which 2 million died. Except for studies of the correlation between TB and HIV/AIDS, the epidemiology of TB in developing countries has been little investigated. The aims of this thesis have been to evaluate risk factors for positive tuberculin skin test (TST), which is the test for diagnosing TB infection, in the population and among TB-case household members, to assess incidence and risk factors for active TB, and to determine clinical predictors for death in TB patients.



A study area in Bissau, the capital of Guinea-Bissau, with a population of about 43,000 has been followed through a demographic census system for over 25 years. In 1996, a TB surveillance system was set up in the area; all adults (age >15 years) with active TB within the chest were included. The background data from the census system allows analyses comparing TB-cases with the whole population.



From 1996 to 2001 a total of 811 TB-cases were included and investigated. The risk of positive TST was closely related to previous or recent exposure to TB, and among the family members of the TB cases the extent of contact was important. BCG vaccination status did not confound the interpretation of the test. TST performed during the early rainy season, from June to August, resulted in smaller reactions, and testing during these months may confound the results. The incidence of active TB in the area was high; 471/100,000 for the adult population. Both HIV-1 and HIV-2 infection greatly increased the risk for TB, although the effect was considerably higher for HIV-1. Other independent risk factors for active TB corresponded well with factors believed to increase the risk also during the epidemic situation in Europe and USA during the 19th and the beginning of the 20th century: male sex, older age, poverty, less schooling and more adults in the family (adult crowding). Interestingly it seemed as if children had a protective influence; children in the household reduced the risk for TB among the adults. The mortality was increased for HIV-1-positive TB-cases, but also co-infection with HIV-2 increased the risk of death compared to HIV-negative. Signs of weakened immune function, such as oral candida infection, and malnutrition increased the risk of dying in both HIV-positive and HIV-negative patients. Estimating the degree of malnutrition using the mid-upper-arm circumference provided a good tool in the evaluation of increased risk for TB death. A civil war 1998-1999 caused involuntary treatment interruption among the patients which considerably increased the mortality, an effect that was most marked in HIV-positive. The increased mortality in HIV-positive TB-cases continued also after the war had ended. (Less)
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author
opponent
  • associate professor Mørkve, Odd, Bergen, Norway
organization
publishing date
type
Thesis
publication status
published
subject
keywords
tuberculin skin test, Infections, Infektioner, survival, mortality, case fatality rate, risk factor, incidence, Guinea-Bissau, Africa, epidemiology, Mycobacterium tuberculosis, HIV-2, HIV-1, HIV, Tbc, Tuberculosis, TB
pages
190 pages
publisher
Per Gustafson, Department of Infectious Diseases, University Hospital MAS, SE-205 02 Malmö, Sweden,
defense location
Patologens föreläsningssal, UMAS
defense date
2003-10-24 09:00
ISBN
91-974795-1-9
language
English
LU publication?
yes
id
1ca8bc91-644b-4976-b7c7-f3798c06862e (old id 466227)
date added to LUP
2007-09-18 19:02:17
date last changed
2016-09-19 08:45:02
@misc{1ca8bc91-644b-4976-b7c7-f3798c06862e,
  abstract     = {Tuberculosis (TB) has plagued the humanity for several thousands of years. The bacteria causing TB is mainly spread from person to person as an aerosol transmission. It is estimated that one third of the world’s population is infected with the disease; about 10% of these will develop active TB during their lifetime. In year 2000, 8 million TB-cases were detected, of which 2 million died. Except for studies of the correlation between TB and HIV/AIDS, the epidemiology of TB in developing countries has been little investigated. The aims of this thesis have been to evaluate risk factors for positive tuberculin skin test (TST), which is the test for diagnosing TB infection, in the population and among TB-case household members, to assess incidence and risk factors for active TB, and to determine clinical predictors for death in TB patients.<br/><br>
<br/><br>
A study area in Bissau, the capital of Guinea-Bissau, with a population of about 43,000 has been followed through a demographic census system for over 25 years. In 1996, a TB surveillance system was set up in the area; all adults (age &gt;15 years) with active TB within the chest were included. The background data from the census system allows analyses comparing TB-cases with the whole population.<br/><br>
<br/><br>
From 1996 to 2001 a total of 811 TB-cases were included and investigated. The risk of positive TST was closely related to previous or recent exposure to TB, and among the family members of the TB cases the extent of contact was important. BCG vaccination status did not confound the interpretation of the test. TST performed during the early rainy season, from June to August, resulted in smaller reactions, and testing during these months may confound the results. The incidence of active TB in the area was high; 471/100,000 for the adult population. Both HIV-1 and HIV-2 infection greatly increased the risk for TB, although the effect was considerably higher for HIV-1. Other independent risk factors for active TB corresponded well with factors believed to increase the risk also during the epidemic situation in Europe and USA during the 19th and the beginning of the 20th century: male sex, older age, poverty, less schooling and more adults in the family (adult crowding). Interestingly it seemed as if children had a protective influence; children in the household reduced the risk for TB among the adults. The mortality was increased for HIV-1-positive TB-cases, but also co-infection with HIV-2 increased the risk of death compared to HIV-negative. Signs of weakened immune function, such as oral candida infection, and malnutrition increased the risk of dying in both HIV-positive and HIV-negative patients. Estimating the degree of malnutrition using the mid-upper-arm circumference provided a good tool in the evaluation of increased risk for TB death. A civil war 1998-1999 caused involuntary treatment interruption among the patients which considerably increased the mortality, an effect that was most marked in HIV-positive. The increased mortality in HIV-positive TB-cases continued also after the war had ended.},
  author       = {Gustafson, Per},
  isbn         = {91-974795-1-9},
  keyword      = {tuberculin skin test,Infections,Infektioner,survival,mortality,case fatality rate,risk factor,incidence,Guinea-Bissau,Africa,epidemiology,Mycobacterium tuberculosis,HIV-2,HIV-1,HIV,Tbc,Tuberculosis,TB},
  language     = {eng},
  pages        = {190},
  publisher    = {ARRAY(0xb0c5448)},
  title        = {Epidemiological aspects of tuberculosis in Guinea-Bissau, West Africa},
  year         = {2003},
}