Incidence Of Acquired Immune Deficiency Syndrome Research Articles

Disease burden of AIDS in last 30-year period and its predicted level in next 25-years based on the global burden disease 2019

BackgroundThis study examines global trends in acquired immune deficiency syndrome (AIDS) incidence, mortality, and disability-adjusted life years (DALYs) from 1990 to 2019, focusing on regional disparities in AIDS incidence, mortality, and DALYs across various levels of socio-demographic index (SDI). It also investigates variations in AIDS incidence, mortality, and DALYs across different age groups, and projects specific trends for the next 25 years.MethodsComprehensive data on AIDS from 1990 to 2019 in 204 countries and territories was obtained from a GBD study. This included information on AIDS incidence, mortality, DALYs, and age-standardized rates (ASRs). Projections for AIDS incidence and mortality over the next 25 years were generated using the Bayesian age-period-cohort model.ResultsFrom 1990 to 2019, the global incidence of HIV cases increased from 1,989,282 to 2,057,710, while the age-standardized incidence rate (ASIR) decreased from 37.59 to 25.24 with an estimated annual percentage change (EAPC) of -2.38. The ASIR exhibited an upward trend in high SDI and high-middle SDI regions, a stable trend in middle SDI regions, and a downward trend in low-middle SDI and low SDI regions. In regions with higher SDI, the ASIR was higher in males than in females, while the opposite was observed in lower SDI regions. Throughout 1990 to 2019, the age-standardized death rate (ASDR) and age-standardized DALY rate remained stable, with EAPCs of 0.24 and 0.08 respectively. Countries with the highest HIV burden affecting women and children under five years of age are primarily situated in lower SDI regions, particularly in sub-Saharan Africa. Projections indicate a significant continued decline in the age-standardized incidence and mortality rates of AIDS over the next 25 years, for both overall and by gender.ConclusionsThe global ASIR decreased from 1990 to 2019. Higher incidence and death rates were observed in the lower SDI region, indicating a greater susceptibility to AIDS among women and < 15 years old. This underscores the urgent need for increased resources to combat AIDS in this region, with focused attention on protecting women and < 15 years old as priority groups. The AIDS epidemic remained severe in sub-Saharan Africa. Projections for the next 25 years indicate a substantial and ongoing decline in both age-standardized incidence and mortality rates.

Influencing factors and knowledge related to AIDS among high-risk male population in Chongqing

This study aims to investigate the influencing factors and Acquired Immune Deficiency Syndrome (AIDS) related knowledge among high-risk male population in Chongqing. A total of 388 men who had sex with their fellow men (MSM) and volunteered for counseling or human immunodeficiency virus (HIV) testing in Chongqing were divided into two groups identified as: aware group (n = 299) and unaware group (n = 89). According to the study subjects, the MSM sentinel surveillance questionnaire of the Chinese Center for Disease Control and Prevention was utilized to investigate their AIDS awareness demographic and behavioral characteristics. Univariate analysis was also applied to analyze the influencing factors of their AIDS knowledge. Binary multivariate logistic analysis was further used to screen the independent risk factors of AIDS inadequate knowledge, leading to the use of regression analysis model. Furthermore, hosmer and lemeshow were employed to test the goodness and fitness of the regression analysis model. Finally, SPSS was used to draw receiver operating characteristic (ROC) curves to evaluate the predictive value of the regression analysis model. Among 388 respondents, 299 participants were aware while 89 participants were unaware of AIDS-related knowledge with an overall awareness rate of 77.06%; univariate and multivariate logistic regression analysis showed that education (high school and below) and household registration (other places) were risk factors for AIDS-related knowledge in high-risk male groups in Chongqing. In addition, a probability model predicted high incidence of AIDS in high-risk male groups in Chongqing because of inadequate AIDS knowledge: P = 1/[1 + exp (1.429 − 1.169X2 − 0.969X3)]. The overall level of awareness of AIDS-related knowledge among high-risk male groups in Chongqing was not high because of low education levels (high school or below) and foreign household registration.

A Combined Model of SARIMA and Prophet Models in Forecasting AIDS Incidence in Henan Province, China.

Acquired immune deficiency syndrome (AIDS) is a serious public health problem. This study aims to establish a combined model of seasonal autoregressive integrated moving average (SARIMA) and Prophet models based on an L1-norm to predict the incidence of AIDS in Henan province, China. The monthly incidences of AIDS in Henan province from 2012 to 2020 were obtained from the Health Commission of Henan Province. A SARIMA model, a Prophet model, and two combined models were adopted to fit the monthly incidence of AIDS using the data from January 2012 to December 2019. The data from January 2020 to December 2020 was used to verify. The mean square error (MSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) were used to compare the prediction effect among the models. The results showed that the monthly incidence fluctuated from 0.05 to 0.50 per 100,000 individuals, and the monthly incidence of AIDS had a certain periodicity in Henan province. In addition, the prediction effect of the Prophet model was better than SARIMA model, the combined model was better than the single models, and the combined model based on the L1-norm had the best effect values (MSE = 0.0056, MAE = 0.0553, MAPE = 43.5337). This indicated that, compared with the L2-norm, the L1-norm improved the prediction accuracy of the combined model. The combined model of SARIMA and Prophet based on the L1-norm is a suitable method to predict the incidence of AIDS in Henan. Our findings can provide theoretical evidence for the government to formulate policies regarding AIDS prevention.

Different Trends of Distinct Time Points of AIDS Events Following HIV Diagnosis in Various At-risk Populations: A Retrospective Nationwide Cohort Study in Taiwan.

IntroductionAcquired immune deficiency syndrome (AIDS) events at distinct time points after human immunodeficiency virus (HIV) diagnosis require various AIDS prevention strategies. However, no nationwide epidemiological surveillance studies have been conducted to explore the trends of distinct AIDS event time points in various at-risk populations. The aim of this study was to explore the issues and characterize the determinants of AIDS status after HIV diagnosis.MethodsThis nationwide cohort study enrolled HIV-positive Taiwanese during 1984–2016. AIDS events were classified into three time points (≤ 3, 4–12, > 12 months) by their occurrence time after HIV diagnosis. The periods of HIV/AIDS diagnosis were divided into six categories according to the calendar year of HIV/AIDS diagnosis: 1984–1991, 1992–1996, 1997–2001, 2002–2006, 2007–2011, and 2012–2016. HIV-positive Taiwanese during 1984–2011 were then selected to determine the factors associated with four AIDS statuses within 5 years after HIV diagnosis (no AIDS, AIDS ≤ 3 months, within 4–12 months, > 12 months) using multinomial logistic regression.ResultsOf 33,142 cases, we identified 15,254 (46%) AIDS events. The overall AIDS incidence (events/100 person-years) peaked during 1992–1996 (20.61), then declined, and finally stabilized from 2002 (8.96–9.82). The evolution of the proportion of distinct time points of AIDS events following HIV diagnosis changed significantly in heterosexuals and intravenous drug users (IDUs) during 1984–2016 (decline at ≤ 3 months in IDUs, decline at 4–12 months in IDUs, and increase at > 12 months in heterosexuals and IDUs) but not among men who have sex with men (MSM). Time points at ≤ 3 months remained at > 50% among MSM and at > 55% among heterosexuals. In multinomial logistic regression, IDUs (vs. men who have sex with men; MSM) had a lower risk of all AIDS statuses; heterosexuals (vs. MSM) had a higher risk of AIDS events ≤ 3 months after HIV diagnosis.ConclusionThe magnitude of AIDS in Taiwan has been stable since 2002. Enhancing early diagnosis among people with sexual contact and optimizing the HIV care continuum among heterosexuals and IDUs should be priorities for further AIDS prevention strategies.

Spatiotemporal Analysis of AIDS Incidence and Its Influencing Factors on the Chinese Mainland, 2005-2017.

Acquired Immune Deficiency Syndrome (AIDS) has become one of the most severe public health issues and nowadays around 38 million people are living with the human immunodeficiency virus (HIV). Ensuring healthy lives and promoting well-being is one of 17 United Nations Sustainable Development Goals. Here, we used the Markov chain matrix and geospatial clustering to comprehensively quantify the trends of the AIDS epidemic at the provincial administrate level in the mainland of China from 2005 to 2017. The Geographically Weighted Regression (GWR) model was further adopted to explore four groups of potential influencing factors (i.e., economy, traffic and transportation, medical care, and education) of the AIDS incidence rate in 2017 and their spatially distributed patterns. Results showed that the AIDS prevalence in southeastern China had been dominant and become prevalent in the past decade. The AIDS intensity level had been increasing between 2008 and 2011 but been gradually decreasing afterward. The analysis of the Markov chain matrix indicated that the AIDS epidemic has been generally in control on the Chinese mainland. The economic development was closely related to the rate of AIDS incidence on the Chinese mainland. The GWR result further suggested that medical care and the education effects on AIDS incidence rate can vary with different regions, but significant conclusions cannot be directly demonstrated. Our findings contribute an analytical framework of understanding AIDS epidemic trends and spatial variability of potential underlying factors throughout a complex extent to customize scientific prevention.

A comparative study on the prediction of the BP artificial neural network model and the ARIMA model in the incidence of AIDS

BackgroundAs a kind of widely distributed disease in China, acquired immune deficiency syndrome (AIDS) has been quickly growing each year, become a serious problem and caused serious damage to the life and health of people and the social events of China and the world because of its high fatality rate. It has been much concerned by all aspects of society. Therefore, developing early warning technology and finding the trend of early development are of quite significance to prevent and control human immunodeficiency virus (HIV)/AIDS. This study aimed to explore a suitable model for the morbidity of AIDS in China and establish a professional and feasible disease prediction model for the prevention and control works of AIDS.MethodsAt present, the traditional linear model is still utilized by most scholars to predict the incidence of HIV/AIDS. In addition, some scholars may attempt to use the nonlinear prediction model. Both prediction models showed good fitting and prediction effects. In China, the incidence of AIDS presents linear and nonlinear characteristics. In this research, the nonlinear back propagation artificial neural network (BP-ANN) model and the typical auto-regressive integrated moving average (ARIMA) linear model were applied to predict the incidence of HIV/AIDS and compare their fitting effects.ResultsBoth models were capable of predicting the expected cases of AIDS. It was seen that ARIMA and BP-ANN models could be used to forecast the monthly incidence of HIV/AIDS, but the fitting and forecasting effects of the nonlinear BP neural network model were better than those of the traditional linear ARIMA model.ConclusionsIn summary, it was further concluded that the BP-ANN model was a suitable way to monitor and predict the change trend and morbidity of AIDS in China.

Temporal trend of HIV/AIDS cases in the state of Minas Gerais, Brazil, 2007-2016.

to analyze the temporal trend of Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) incidence, detection and mortality coefficients in the state of Minas Gerais between 2007 and 2016. this was a time series study of data held on the Notifiable Health Conditions Information System (Sinan) using Prais-Winsten regression. in the period studied, 35,349 cases were notified, with predominance of sexually transmitted cases (81.7%), 50.3% of which were heterosexual cases and 22.8% were homosexual cases. AIDS incidence increased (annual change 1.6%; 95%CI 0.0;3.3) as did HIV detection (annual change 60.3%; 95%CI 22.9;109.0). The mortality rate was stationary; HIV+ notifications increased from 3.8% in 2007 to 65.1% in 2016. the growing trend of HIV+ detection coincided with the government strategy to identify cases. AIDS incidence increased.

Visceral leishmaniasis lethality in Brazil: an exploratory analysis of associated demographic and socioeconomic factors.

INTRODUCTION: It is believed that delays in diagnosis and treatment of Visceral Leishmaniasis (VL) contribute significantly to the burden of VL lethality in Brazil. METHODS: This study included several parts: a descriptive cross-sectional study of the individual characteristics of deaths from disease; a descriptive ecological study of the spatial distribution of deaths from disease; and an ecological analytical study to evaluate the association between disease lethality rates and the demographic, socioeconomic, and health indicators. The study population comprised all cases diagnosed throughout the country per the National Disease Notification System (SINAN) and the total number of disease deaths recorded in the Mortality Information System (SIM) from 2007 to 2012. RESULTS: Of the 223 deaths from disease captured by pairing the databases, 59.1% were reported as "death from other causes". There were significant associations between VL lethality rate and municipalities with the highest proportion of vulnerable individuals (rate ratio (RR)=1.18, 95% confidence interval (CI): 1.01-1.27), with VL lower incidence rate (RR=0.62, 95% CI: 0.58-0.67) and a higher incidence rate of Acquired Immune Deficiency Syndrome (AIDS) (RR=1.20, 95% CI: 1.17-1.51). CONCLUSIONS: Linking the SINAN and SIM databases allowed the inclusion of 14% of otherwise underreported deaths from VL for the study period, showing that this method is useful for the surveillance of VL-related deaths. The size of the municipal population, proportion of the vulnerable population, incidence of disease, and the incidence of AIDS were associated with municipal lethality rates related to VL in Brazil.

Trends in the Epidemiology of Sexually Transmitted Disease, Acquired Immune Deficiency Syndrome (AIDS), Gonorrhea, and Syphilis, in the 31 Provinces of Mainland China.

BackgroundThis study aimed to investigate trends in the epidemiology of the leading sexually transmitted diseases (STDs), acquired immune deficiency syndrome (AIDS), gonorrhea, and syphilis, in the 31 provinces of mainland China.Material/MethodsThis retrospective study analyzed the incidence data of STDs from official reports in China between 2004 and 2016. The grey model first order one variable, or GM (1,1), time series forecasting model for epidemiological studies predicted the incidence of STDs based on the annual incidence reports from 31 Chinese mainland provinces. Hierarchical cluster analysis was used to group the prevalence of STDs within each province.ResultsThe prediction accuracy of the GM (1,1) model was high, based on data during the 13 years between 2004 and 2016. The model predicted that the incidence rates of AIDS and syphilis would continue to increase over the next two years. Cluster analysis showed that 31 provinces could be classified into four clusters according to similarities in the incidence of STDs. Group A (Sinkiang Province) had the highest reported prevalence of syphilis. Group B included provinces with a higher incidence of gonorrhea, mainly in the southeast coast of China. Group C consisted of southwest provinces with a higher incidence of AIDS.ConclusionsThe GM (1,1) model was predictive for the incidence of STDs in 31 provinces in China. The predicted incidence rates of AIDS and syphilis showed an upward trend. Regional distribution of the major STDs highlights the need for targeted prevention and control programs.

The spatial distribution pattern of human immunodeficiency virus/acquired immune deficiency syndrome in China

Human immunodeficiency virus (HIV) infection and the acquired immune deficiency syndrome (AIDS) exhibit variable patterns among the provinces of China. Knowledge of the geographical distribution of the HIV/AIDS epidemic is needed for the prevention and control of AIDS. Thus, the cumulative number of reported cases of HIV/AIDS from the period 1985-2013, and the incidence rate of AIDS in 2013 were determined. Spatial autocorrelation analysis and hotspot analysis were conducted using ArcGIS10.2 to explore the spatial distribution of the HIV/AIDS epidemic. Both the thematic map and the global spatial autocorrelation Moran's I statistics revealed a clustered distribution of the spatial pattern. A local spatial autocorrelation analysis indicated hotspots of AIDS incidence rate that were confined to the provinces of Guangxi, Yunnan and Sichuan. The hotspots encompassed Guangxi and Yunnan, while Henan Province displayed a negative autocorrelation with more variable numbers that included neighbouring regions. The Getis-Ord Gi* statistics identified 6 hotspots and 8 coldspots for the incidence of AIDS, and 7 hotspots and 1 coldspot for the cumulative number of reported cases of HIV/AIDS. The spatial distribution pattern of the HIV/AIDS epidemic in China is clustered, demonstrating hotspots located in the Southwest. Specific interventions targeting provinces with severe HIV/AIDS epidemic are urgently needed.

Risk Factors for Advanced HIV Disease and Late Entry to HIV Care: National 1994-2012 HIV Surveillance Data for Wuhan, China.

Few studies in China have focused on advanced human immunodeficiency virus (HIV) disease (AHD) and late entry to HIV care, which are associated with increased morbidity and mortality. A population-based retrospective study was conducted using 980 national HIV surveillance reports from 1994 to February 2012 in Wuhan, China. AHD was defined as presence of a first-reported CD4 count<200 cells/μL or an acquired immune deficiency syndrome (AIDS)-defining event within 1 month of HIV diagnosis. Late entry to HIV care was defined as patients with a first-reported CD4 cell count>6 months after diagnosis. Non-conditional logistic regression analysis was used to identify factors associated with AHD, late entry to HIV care, and AIDS within 1 year of HIV diagnosis. The proportions of AHD, AIDS within 1 year of HIV diagnosis, and late entry to HIV care were 29.49%, 39.39%, and 20.84%, respectively. Most of the deaths (74.27%, 127/171) occurred within 1 year of diagnosis. Short-term mortality, proportion of AHD, and late entry to HIV care showed a similar downward trend from pre-2003 to 2011 (p<0.001). Age, transmission category, sample source, and occupation were associated with AHD, late entry to HIV care, and AIDS within 1 year of HIV diagnosis in the multivariate logistic regression analysis. These findings indicate that AHD and late entry to HIV care were associated with an increased incidence of AIDS or death, particularly within 1 year of diagnosis. More effort should be made to assure early diagnosis and timely entry to care.

AIDS patients with tuberculosis: characteristics and trend of cases reported to the National AIDS Registry in Italy--1993-2010

The co-infection of tuberculosis (TB) and human immunodeficiency virus (HIV) continue to be a severe problem in the European region. We estimated the extent of this phenomenon in Italy, describing and analysing the characteristics of persons with acquired immune deficiency syndrome (AIDS) and TB reported to the National AIDS Registry. We analysed the cases of TB reported to the National AIDS Registry in Italy since 1993, the year in which TB was introduced as an AIDS-defining disease. From 1993 to 2010, 45,403 cases of AIDS were reported; among these, 4075 (8.9%) had TB (any location). Since 1993, there has been a progressive increase in the proportion of persons with TB, from 6.8% in 1993 to 11.0% in 2010. Men accounted for 76.3%; the median age at diagnosis was 35 years (interquartile range: 31-42 years), and 34.1% were non-nationals. Compared with AIDS cases without TB, AIDS cases with TB were significantly associated with young age (≤33 years), being non-Italian, having heterosexual contacts, living in the south of Italy, being a late tester and being alive at the time of data analysis. The proportion of non-nationals increased from 10.8% in 1993 to 64.6% in 2010. The incidence of AIDS and TB among non-nationals for the whole study period was 2.97 cases per 100,000 non-nationals, compared with 0.11 cases per 100,000 Italians. These data suggest that the occurrence of TB among persons with AIDS is also increasing in Italy, with an increasing proportion of non-nationals, and emphasize the need to undergo HIV screening for all persons diagnosed with TB.

Selected factors in predisposition to HIV and AIDS: Implications for educational policy and practice

The purpose of this paper is to illuminate a gendered view of the importance of biological age and gender inequality in predisposition to the Human Immune Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS), and implications for requisite educational policies and best practice. Cognizant of the increasing age-based and gender inequality as factors in vulnerability women and girls face in Botswana. This paper is based on a critical review of deliberations and expressed opinions of workshop participants of a qualitative methodological workshop in a series of four sensitization workshops conducted in four areas in Botswana, namely the capital city of Gaborone, Lobatse town and two villages of Tsabong and Serowe between November 2007 and February 2008. Using Botswana as a point of contact, and informed by a combined epistemological base of age and gender inequality, and the PEN 3 model as analytical tools, and the author argues that age and gender inequality are some of the global factors that predispose women, and to a lessor extent, men, to the adverse prevalence, incidence and effects of HIV and AIDS. A conclusion drawn from the workshop series is that educators and policy makers need to periodically revisit administration practices and policies and ensure that they promote best practice in the global multi-sectoral responses to HIV and AIDS. Context specific formal and non-formal educational administration, formulation and enforcement of policies that promote best practice are very important in the global management of HIV and AIDS. Key words: Selected factors, predisposition to HIV/AIDS in Botswana.

Causes of Death in Pediatric Patients Vertically Infected by the Human Immunodeficiency Virus Type 1 in Madrid, Spain, From 1982 to Mid-2009

Effective therapies have increased life expectancy of human immunodeficiency virus (HIV)-infected pediatric patients. We investigated the underlying causes of death, mortality, and acquired immune deficiency syndrome (AIDS) rates in HIV-infected pediatric patients in Madrid, Spain. We studied a multicenter cohort of 478 HIV-infected pediatric patients in Madrid. Mortality and AIDS incidence rates, causes of death, CD4 T-cell, and HIV RNA were analyzed during calendar periods (CPs): pre-HAART (highly active antiretroviral therapy) (CP1: 1982-1996) and post-HAART era (CP2: 1997-2009). During 5690 person-years of follow-up 157 (32.8%) deaths occurred. Median age at death increased (CP1: 3.2 years [1.0-6.3] vs. CP2: 7.7 years [3.1-11.4]; P < 0.01). Mortality and AIDS rates decreased 10.6-fold (95% confidence intervals [CI]: 6.9-16.7) and 6.9-fold (95% CI: 5.0-9.6), respectively, between CPs. Nevertheless, mortality was 10.4-fold (95% CI: 5.8-18.8; P < 0.001) higher than in age-similar general population in late-CP2. In all, 169 causes of death were reported. Multiple causes were reported in 16 of 151 (10.6%) patients. In 81.1% (137/169), the causes were AIDS-defining, 11.8% (20/169) HIV-related, and 7.1% (12/169) non-HIV-related. Infections were the leading causes (60.8%, 101/166); from 1999 to 2007 the risk of death from infections was 115.9 times (95% CI: 42.0-265.8; P < 0.001) higher than in the age-similar general population. Comorbidity was reported in 66.9% (101/151) of patients. Median HIV-1 RNA at death decreased (CP1: 5.9 [5.0-6.3]; CP2: 5.3 [4.2-5.8]; P < 0.01). Despite decline in mortality and AIDS rates, it is important to monitor all causes of death as prolonged survival might allow underlying comorbidity to become more clinically relevant.

Endemic fungal infections in the Asia-Pacific region

Endemic mycoses are important fungal infections in their respective habitats. In the Asia-Pacific region, an accurate epidemiological picture of endemic mycoses is elusive; few epidemiological surveys have been performed, and limited laboratory facilities and experience with fungal infections have further hampered recognition of infection. However, pockets of endemicity do indeed exist, and endemic fungal infections can have a significant impact on public health. This article reviews the most common endemic mycoses in the Asia-Pacific region: histoplasmosis, penicilliosis, and sporotrichosis. Blastomycosis, which has been infrequently reported within the region, is also briefly discussed. Certain areas of the Asia-Pacific region are endemic for histoplasmosis; however, the ecologic niche for this infection remains unclear. Penicilliosis is restricted to Southeast and Eastern Asia, whereas sporotrichosis is encountered in tropical areas of the Asia-Pacific region linked to environmental reservoirs distinct from those seen in the Western world. Before the advent of acquired immune deficiency syndrome (AIDS), histoplasmosis and penicilliosis were only occasionally reported; however, the incidence of both mycoses has increased with the rise in the incidence of AIDS. Comprehensive studies are needed to fully assess the areas of endemicity and the impact of endemic mycoses in the Asia-Pacific region.

HIV and hemophilia

HIV and hemophilia

Knowledge of AIDS, perceived risk of AIDS, and at-risk sexual behaviors among older adults.

To identify older adults' knowledge of acquired immune deficiency syndrome (AIDS), perceptions of their risk of AIDS, and at-risk behaviors by using a questionnaire derived from the health belief model. A descriptive correlation design was used to survey persons 50 years of age and older who participate in university-based senior programs. The sample of 166 persons (55% return rate) had a mean age of 71 years and included 33% males. The sample is representative of the participants in these programs. Five hypotheses based on the health belief model were tested. Statistical analyses showed significant predictors of the likelihood of using recommended safe sexual practices were gender, knowledge of AIDS, perceived susceptibility to AIDS, and perceived threat of AIDS. The results indicated the respondents were knowledgeable about human immunodeficiency virus (HIV) transmission through casual contact and medical aspects of AIDS. Although the respondents recognized the seriousness of AIDS, they generally did not believe that they were susceptible to this disease, even though about 10% indicated sexual activity outside of a long-term relationship. The study findings support the need for nurse practitioners to assess sexual behaviors in and provide information about safe sex practices to older clients because of the documented rising incidence of AIDS in persons over 50 years of age.

A mathematical treatment of AIDS and condom use

In this paper we examine the impact of condom use on the sexual transmission of human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) amongst a homogeneously mixing male homosexual population. We first derive a multi-group SIR-type model of HIV/AIDS transmission where the homosexual population is split into subgroups according to frequency of condom use. Both susceptible and infected individuals can transfer between the different groups. We then discuss in detail an important special case of this model which includes two risk groups and perform an equilibrium and stability analysis for this special case. Our analysis shows that this model can exhibit unusual behaviour. As normal, if the basic reproduction number, R0, is greater than unity then there is a unique disease-free equilibrium which is locally unstable and a unique endemic equilibrium. However, when R0 is less than unity two endemic equilibrium solutions can also co-exist simultaneously with the disease-free solution which is locally stable. Numerical simulations using realistic parameter values confirm this and we find that in certain circumstances the disease-free solution and one of the endemic solutions are both locally asymptotically stable, while the other endemic solution is unstable. This unusual behaviour has important implications for control of the disease as reducing R0 to less than unity no longer guarantees eradication of the disease. For a restricted special case of this two-group model we show that there is only the disease-free equilibrium for R0 < or = 1 which is globally stable. For R0 > 1 the disease-free equilibrium is unstable and there is a unique endemic equilibrium which is locally stable. We then attempt to fit the model to HIV and AIDS incidence data from San Francisco, USA. The paper concludes with a brief discussion.

A mathematical treatment of AIDS and condom use

In this paper we examine the impact of condom use on the sexual transmission of human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) amongst a homogeneously mixing male homosexual population. We first derive a multigroup SIR‐type model of HIV/AIDS transmission where the homosexual population is split into subgroups according to frequency of condom use. Both susceptible and infected individuals can transfer between the different groups. We then discuss in detail an important special case of this model which includes two risk groups and perform an equilibrium and stability analysis for this special case. Our analysis shows that this model can exhibit unusual behaviour. As normal, if the basic reproduction number, R0, is greater than unity then there is a unique disease‐free equilibrium which is locally unstable and a unique endemic equilibrium. However, when R0 is less than unity two endemic equilibrium solutions can also co‐exist simultaneously with the disease‐free solution which is locally stable. Numerical simulations using realistic parameter values confirm this and we find that in certain circumstances the disease‐free solution and one of the endemic solutions are both locally asymptotically stable, while the other endemic solution is unstable. This unusual behaviour has important implications for control of the disease as reducing R0 to less than unity no longer guarantees eradication of the disease. For a restricted special case of this two‐group model we show that there is only the disease‐free equilibrium for R0 ≤ 1 which is globally stable. For R0 > 1 the disease‐free equilibrium is unstable and there is a unique endemic equilibrium which is locally stable. We then attempt to fit the model to HIV and AIDS incidence data from San Francisco, USA. The paper concludes with a brief discussion.

Incidence of acquired immune deficiency syndrome (AIDS) and other sexually transmitted diseases (STD) in Abia State, Nigeria

Medical records of two government-owned hospitals‐Federal Medical Centre (FMC). Umuahia and Abia State University Teaching Hospital (ABSUTH), Aba‐were examined for confirmed sexually transmitted diseases (STD) including acquired immune deficiency syndrome (AIDS). At the FMC, data from samples collected five years before (1987‐1991) and five years after (1992‐1996) the creation of Abia State, were analysed. Data from samples obtained from ABSUTH were those collected during the five years 1992‐1996. The STD observed were candidiasis, AIDS, gonorrhoea, trichomoniasis and syphilis. Candidiasis was common in both hospitals and accounted for 87.6% of all the STD cases during 1987‐1991 at the FMC. Incidence of AIDS was 32.9% at the FMC and 20.1% at ABSUTH during the period 1992‐1996. Comparison of the percentage prevalence of the STD showed that more cases of candidiasis were recorded before than after the State's creation. Also candidiasis and AIDS were more prevalent at the FMC than at ABSUTH during 1992‐1996, while gonorrhoea, syphilis and trichomoniasis were more prevalent at ABUSTH. Statistical analysis of data showed no significant difference at the 95% confidence limit between the two health institutions and between the two periods of study at the FMC.