Trends of HIV Infection in the Kagera Region of Tanzania 1987-2000
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U m e å U n iv e r s it y M e d ic a l D issertations New Series No 710 - ISSN 0346-6612 - ISBN 91-7191-966-x From Epidemiology, Department of Public Health and Clinical Medicine Umeå University, SE-901 85 Umeå, Sweden and Department of Epidemiology and Biostatistics Institute of Public Health, Muhimbili University College of Health Sciences University of Dar es Salaam, Tanzania Trends of HIV infection in the Kagera region of Tanzania 1987-2000 Gideon Kwesigabo AKADEMISK AVHANDLING som med vederbörligt tillstånd av Rektorsämbetet vid Umeå universitet för avläggande av medicine doktorsexamen kommer att offentligt försvaras i Sal B, 9 tr, Tandläkarhögskolan i Umeå fredagen den 6 april 2001, kl. 13.00. Fakultetsopponent: Dr Knut Fylkesnes, Institutt for samfunnsmedisin, Universitetet i Tromso samt Centre for international Health, Universitetet i Bergen Avhandlingen försvaras pä engelska Umeå 2001 Trends of HIV infection in the Kagera region of Tanzania 1987-2000. G ideon K w esigabo. Epidemiology, Department of Public Health and Clinical Medicine, Umeå University, SE-901 85 Umeå, Sweden and Department of Epi demiology and Biostatistics, Institute of Public Health, Muhimbili University College of Health Sciences, University of Dar es Salaam, Tanzania A bstract Disease trends provide information about past, current and may help to predict future patterns of diseases. These are important for planning future health needs and formulation of public health policy. This thesis aims at describing the Kagera HIV/AIDS epidemic in terms of magnitude and trends in various populations and areas of varying levels of HIV infection, and to investigate factors associated with these trends. An alternative means of monitoring the epidemic, using pregnant women as a sentinel population is assessed. As a quality control measure, the HIV laboratory testing strategy is also evaluated. A multi-method approach was adopted in addressing these objectives. General population-based cross-sectional studies, prospective cohort studies, sentinel surveillance studies, hospital and laboratory based studies were among the study designs/methods used to answer the objectives. Findings from a region- wide cross-sectional study in 1987, indicated a high prevalence of HIV-1 infection, infection levels decreasing with increasing distance from Bukoba urban district. For subsequent monitoring of trends, based on these varying levels of infection, three districts were selected to represent high, medium and low levels of HIV-1 infection in the region. From 1987 to 2000 a declining trend of HIV-1 infection was observed in the study area. Initially the overall age-adjusted prevalence in the high prevalence area (Bukoba urban district) was 32.8% among hospitalized patients and 24.2% in the general population. From 24.2% in 1987 in the general population, the prevalence declined to 18.2% in 1993 and later to 13.3% in 1996. For the medium HIV-1 prevalence area (Muleba district), the overall age- adjusted prevalence declined from 10.0% in 1987 to 6.8% in 1996 and to 4.3% in 1999. In the low HIV-1 prevalence area (Karagwe district), the age- adjusted prevalence declined from 4.5% in 1987 to 2.6% in 1999. In all the three areas the most significant prevalence decline was observed among females in the age group 15-24 years. No age group exhibited a significant upward trend. Incidence in the high prevalence area, declined from 47.5/1000 PYAR in 1989 to 9.1/1000 PYAR in 1996. For the medium prevalence area, incidence declined from 8.2/1000 PYAR in 1989 to 3.9/1000 PYAR in year 2000. Findings regarding behavioural factors indicated a rise in condom use, the proportion of individuals getting married increased with time and they were getting married at an early age. Age at first sexual intercourse decreased over time. Over 80% of studied individuals reported to have one sex partner and over 96% of individuals in the three areas indicated that they took some form of precaution against HIV infection, mainly sticking to one partner. The studies also indicated that sentinel surveillance using pregnant women attending an antenatal clinic for the first time during a particular pregnancy underestimated the general population prevalence when used for single point comparisons but was useful in monitoring the epidemic. The benefits of using this group outweighed limitations of possible selection bias. The HIV antibody testing strategy utilizing two sequential ELISAs based on different testing principles was found to be a valid and feasible means of monitoring trends. It is therefore concluded that there has been a decline in the prevalence and incidence of HIV-1 infection in areas of varying levels of HIV-1 infection in the Kagera region, especially so among young women. These findings with a declining trend in HIV-infection also in low-prevalence areas, where the epidemic could not have reached saturation, indicate that behavioural changes at individual level have resulted into this decline in the epidemic. Regarding alternative means of monitoring the epidemic, continued surveillance of the epidemic based on antenatal clinic attendees as a sentinel population was recommended. Despite these observations from the study area, the general population still remains at risk of HIV infection and all efforts responsible for bringing the magnitude down should continue unabated otherwise laxity in the intervention activities may result into a resurgence of the epidemic. Key words: HIV infection, prevalence trends, incidence trends, declining trends, ANC sentinel surveillance, Kagera, Tanzania U m e å U n iv e r sit y M e d ic a l D issertations New Series No 710 - ISSN 0346-6612 From Epidemiology, Department of Public Health and Clinical Medicine Umeå University, SE-901 85 Umeå, Sweden and Department of Epidemiology and Biostatistics Institute of Public Health, Muhimbili University College of Health Sciences University of Dar es Salaam, Tanzania Trends of HIV infection in the Kagera region of Tanzania 1987-2000 Gideon Kwesigabo Umeå 2001 Epidemiology Department of Public Health and Clinical Medicine “J Umeå University, Sweden Department of Epidemiology and Biostatistics Institute of Public Health, Muhimbili University College of Health Sciences University of Dar es Salaam, Tanzania ISBN 91-7191-966-x © Copyright: Gideon Kwesigabo Photographs: Maria Emmelin Printed in Sweden by Larsson & Co:s Tryckeri AB, Umeå, 2001 Epidemiology Department of Public Health and Clinical Medicine Umeå University, SE-901 85 Umeå, Sweden -II- A bstr a c t Disease trends provide information about past, current and may help to predict future patterns of diseases. These are important for planning future health needs and formulation of public health policy. This thesis aims at describing the Kagera HIV/AIDS epidemic in terms of magnitude and trends in various populations and areas of varying levels of HIV infection, and to investigate factors associated with these trends. An alternative means of monitoring the epidemic, using pregnant women as a sentinel population is assessed. As a quality control measure, the HIV laboratory testing strategy is also evaluated. A multi-method approach was adopted in addressing these objectives. General population-based cross-sectional studies, prospective cohort studies, sentinel surveillance studies, hospital and laboratory based studies were among the study designs/methods used to answer the objectives. Findings from a region- wide cross-sectional study in 1987, indicated a high prevalence of HIV-1 infection, infection levels decreasing with increasing distance from Bukoba urban district. For subsequent monitoring of trends, based on these varying levels of infection, three districts were selected to represent high, medium and low levels of HIV-1 infection in the region. From 1987 to 2000 a declining trend of HIV-1 infection was observed in the study area. Initially the overall age-adjusted prevalence in the high prevalence area (Bukoba urban district) was 32.8% among hospitalized patients and 24.2% in the general population. From 24.2% in 1987 in the general population, the prevalence declined to 18.2% in 1993 and later to 13.3% in 1996. For the medium HIV-1 prevalence area (Muleba district), the overall age- adjusted prevalence declined from 10.0% in 1987 to 6.8% in 1996 and to 4.3% in 1999. In the low HIV-1 prevalence area (Karagwe district), the age- adjusted prevalence declined from 4.3% in 1987 to 2.6% in 1999. In all the three areas the most significant prevalence decline was observed among females in the age group 13-24 years. No age group exhibited a significant upward trend. Incidence in the high prevalence area, declined from 47.5/1000 PYAR in 1989 to 9.1/1000 PYAR in 1996. For the medium prevalence area, incidence declined from 8.2/1000 PYAR in 1989 to 3.9/1000 PYAR in year 2000. Findings regarding behavioural factors indicated a rise in condom use, the proportion of individuals getting married increased with time and they were getting married at an early age. Age at first sexual intercourse decreased over time. Over 80% of studied individuals reported to have one sex partner and over 96% of individuals in the three areas indicated that they took some form of precaution against HIV infection, mainly sticking to one partner. The studies also indicated that sentinel surveillance using pregnant women attending an antenatal clinic for the first time during a particular pregnancy underestimated the general population prevalence when used for single point comparisons but was useful in monitoring the epidemic. The benefits of using this group outweighed limitations of possible selection bias. -Ill- The HIV antibody testing strategy utilizing two sequential ELISAs based on different testing principles was found to be a valid and feasible means of monitoring trends. It is therefore concluded that there has been a decline in the prevalence and incidence of HIV-1 infection in areas of varying levels of HIV-1 infection in the Kagera region, especially so among young women.