AIDS Incidence Research Articles

The fall after the rise: Tuberculosis in the United States, 1991 through 1994.

Factors associated with decreases in tuberculosis cases observed in the United States in 1993 and 1994 were analyzed. Changes in case counts reported to the national surveillance system were evaluated by dividing the number of incident cases of TB reported in 1993 and 1994 by the number of cases reported in 1991 and 1992 and stratifying these ratios by demographic factors, AIDS incidence, and changes in program performance. Case counts decreased from 52,956 in 1991 and 1992 to 49,605 in 1993 and 1994 (case count ratio = 0.94, 95% confidence interval [CI] = 0.93, 0.95). The decrease, confined to US-born patients, was generally associated with AIDS incidence and improvements in completion of therapy, conversion of sputum, and increases in the number of contacts identified per case. Recent TB epidemiology patterns suggest that improvements in treatment and control activities have contributed to the reversal in the resurgence of this disease in US-born persons. Continued success in preventing the occurrence of active TB will require sustained efforts to ensure appropriate treatment of cases.

Predicting the incidence of AIDS from 1980 to 1995.

Social indices for American states in 1980 predicted 79% of the variance in the incidence of AIDS in the United States of America in 1995.

Flexible assessment of trends in age-specific HIV incidence using two-dimensional penalized likelihood.

We present a method for estimating age- and time-specific HIV incidence using back-calculations of AIDS incidence data. Two-dimensional penalized likelihood is employed, using a flexible bivariate step function model of HIV incidence, together with a quadratic roughness penalty which leads to thin-plate spline smoothing. This allows incidence estimates to vary flexibly and smoothly in both age and time. We propose generalized cross-validation as a guide for choice of an appropriate level of smoothing and describe an EM algorithm for computing the estimates. We propose the method primarily for qualitative assessment of trends in age-specific incidence over time and apply it to a small Italian data set on men who have sex with men. The analysis suggests a trend over time of increasing relative incidence among younger individuals, consistent with incidence patterns observed in other countries.

Recommendations for HIV surveillance in Europe.

The HIV/AIDS epidemic in Europe is now at an important turning point. In western Europe, AIDS incidence has been declining since 1996, partly as a result of new, more effective treatment of HIV infections. As these treatments delay the progression of HIV

Declines in AIDS Incidence Associated with Highly Active Anti-Retroviral Therapy (HAART) Are Not Reflected in KS and Lymphoma Incidence.

Declines in AIDS Incidence Associated with Highly Active Anti-Retroviral Therapy (HAART) Are Not Reflected in KS and Lymphoma Incidence.

HHV-8 Infection in Homosexual Men From New York City (NYC) and Washington (DC): Frequency, Risk Factors, and Relationship to Kaposi's Sarcoma (KS)

57 Background: The observations that HHV-8 is etiologically linked to KS and that KS is much commoner in homosexual men than in other HIV-1 risk groups suggest that HHV-8 is a non-ubiquitous, sexually transmitted infection. To clarify the epidemiology of HHV-8 and its relationship to KS, we measured antibodies to HHV-8 longitudinally in homosexual men from two U.S. cities. Methods: In 1982, 245 homosexual men without evidence of AIDS were enrolled in a prospective study of AIDS incidence. We collected blood specimens and sexual behavior information anually; follow-up of HIV-1-uninfected men ceased in 1991. Antibodies to latent HHV-8 antigens were measured in all serum specimens of sufficient volume by an immunofluorescence assay. We used X2 tests for statistical testing and Kaplan-Meier methods to examine the risk of KS after infection with both HIV-1 and HHV-8. Results: The prevalence of HHV-8 at study entry was 40% among NYC subjects and 14.5% among DC subjects (RR, 2.8; p=0.001). HHV-8 prevalence was also associated with HIV-1 infection (RR 3.4; p=0.001) and number of sex partners (p=0.001, X2 for trend), but the higher prevalence in NYC men persisted after considering these variables. DC men with one or more sex partners from NYC were 3.1-fold more likely to be infected with HHV-8 at study entry (p=0.01) than were DC men with no NYC partners. The incidence of HHV-8 infection subsequent to study entry was similar regardless of residence (NYC, 0.04/person-year; DC, 0.03/person-year; p=0.5), but was strongly associated with the number of sex partners (p=0.001, X2 for trend). Among 60 men infected with both HHV-8 and HIV-1, 15 have developed KS at a median of 45 months (range, 12 to 154 months); the ten-year KS-free survival among these dually-infected men was 62%. Conclusions: 1) HHV-8 infection was common among these homosexual men in the early 1980's, especially those residing in or having sex partners from NYC. This geographic difference in HHV-8 prevalence is consistent with differences in the KS risk reported among homosexual men from these cities. 2) HHV-8 prevalence and incidence were strongly associated with the number of sex partners in this population. 3) Persons infected with both HHV-8 and HIV-1 are at high risk of developing KS; the time from dual infection with these viruses to the diagnosis of KS varies widely and may exceed a decade.

Increasing Incidence of AIDS Among Women

Increasing Incidence of AIDS Among Women

A birth cohort analysis of AIDS in Europe

To study trends in AIDS incidence in Europe by age and year of birth. Age-period-cohort analyses were adopted to distinguish the different time factors of calendar year, age and year of birth. Non-aggregate AIDS incidence data from 12 European countries (1978-1994) were adjusted for reporting delay and expressed per unit of population (per 100000 persons or 100000 person-years). Age-specific incidence patterns (absolute level and rate of increase) were compared between 5-year birth cohorts for homo-/bisexual men, injecting drug users (IDU) and heterosexual contact cases. Mean age at diagnosis increased strongly amongst IDU, but less so among homo-/bisexual men and heterosexual contact cases. Of a total 110646 reported cases (116311 after adjustment for reporting delay), 87167 (78.8%) were among people born in 1950-1974 [91951 (79.1%) after adjustment for reporting delay]. The relative impact on specific birth cohorts differed strongly by exposure group. Incidences at age ranges of 20-24 and 25-29 years among cohorts born in 1965 and after were about the same level (homo-/bisexual men, IDU) or higher (heterosexual contact cases) than older birth cohorts when these were in the same age range; rates of increase were less among homo-/bisexual men and IDU, but higher among heterosexuals. There were large differences between counties. Overall, AIDS incidence among cohorts born in 1965 and after is about the same level (homo-/bisexual men, IDU) or higher (heterosexual contact cases) than older cohorts when these were in the same age range. Rates of increase of AIDS incidence curves suggest reduced HIV transmission amongst the most recent cohorts of homo-/bisexual men and IDU, but among young heterosexuals the epidemic is still expanding.

Effect of HAART on natural history of AIDS-related opportunistic disorders

The remarkable activity against HIV of regimens that contain protease inhibitors, termed highly active antiretroviral therapy (HAART), has received much attention. Use of protease inhibitors, in combination with other active agents, has led to a striking reduction in AIDS-associated morbidity and mortality, the first such improvement since the recognition of the HIV epidemic in 1981. 1 Centers for Disease Control and PreventionUpdate: trends in AIDS incidence. Morbid Mortal Weekly Rep. 1997; 46: 165-173 PubMed Google Scholar Focal mycobacterial lymphadenitis following initiation of protease-inhibitor therapy in patients with advanced HIV-1 diseaseThe initiation of indinavir therapy in patients with CD4 counts of less than 50 cells/mL and subclinical MAC infection may be associated with a severe illness, consisting of fever (>39°C), leucocytosis, and lymphadenitis (cervical, thoracic, or abdominal). The intense inflammatory reactions that make admission to hospital necessary may be secondary to significant numbers of functionally competent immune cells becoming available to respond to a heavy mycobacterial burden. Prophylaxis or screening for subclinical MAC infection, or both, should therefore be done before the beginning of protease-inhibitor therapy in patients with advanced HIV infection. Full-Text PDF Treatment of HIV-1-associated microsporidiosis and cryptosporidiosis with combination antiretroviral therapyCombination antiretroviral therapy that includes a protease inhibitor can restore immunity to E bieneusi or C parvum in HIV-1 infected individuals, and result in complete clinical, microbiological, and histological responses. The persistent CD8 cell and macrophage infiltrate, and the rapid time to relapse in patients with declining CD4 lymphocyte counts, suggest that neither infection was eradicated. Full-Text PDF

Recent trends in the HIV epidemic in adolescent and young adult gay and bisexual men.

To explore recent patterns in the HIV epidemic in young gay and bisexual men, we analyzed national AIDS surveillance data for men who have sex with men (MSM) 13 to 25 years of age. Estimates of annual AIDS incidence were calculated by adjusting the surveillance data for reporting delays, unreported HIV risks, and the 1993 change in the AIDS case definition. Between 1990 and 1995, estimated AIDS incidence in young MSM declined 29%, from 1400 to 1000 cases; however, trends in incidence varied greatly by race/ethnicity. Annual AIDS incidence decreased 50% in whites during this period (from 720 to 360), but fell just 2% in blacks (from 430 to 420) and rose 5% in Hispanics (from 220 to 230). Trends in incidence also differed by metropolitan statistical area (MSA) size. Between 1990 and 1995, AIDS incidence declined 37% in MSAs with populations of 2,500,000 people or more and 28% in MSAs with 1,000,000 to 2,499,999 people, but incidence decreased only 15% in MSAs with 500,000 to 999,999 people, and 13% in MSAs with 50,000 to 499,999. Incidence in nonmetropolitan (i.e., rural) areas was unchanged. Young black and Hispanic MSM now account for most young MSM with AIDS, and incidence in young MSM in small MSAs and rural areas has been relatively constant. Trends in AIDS incidence indicate that levels of HIV infection have remained persistently high in certain populations of young MSM, underscoring the immense need for HIV prevention programs targeted specifically toward these young men.

HIV Prevention Knowledge, Attitudes, and Sexual Practices of Asian College Students

While Asian Americans remain one of the ethnic groups least affected by AIDS, recent data suggests that this may be changing. The incidence of AIDS in the Asian community is increasing. The purpose of this study was to explore the knowledge, attitudes, and sexual practices of a sample of Asian college students. Data were collected from students enrolled at six colleges and universities in a southeastern metropolitan area (n = 2,044). For this analysis, respondents who reported that they were of Asian background and unmarried were included (n = 128). Twenty percent of the subsample (n = 26) indicated they had grown up outside the United States. Descriptive analyses were done by gender and country of early development (U.S. vs. foreign-reared). Results indicated that males were more sexually active, more likely to use condoms and had less positive attitudes toward abstinence than females. U.S.-reared students initiated intercourse at a younger age and had higher knowledge scores than foreign-reared students. Compared to students of other ethnic groups, Asian students initiated intercourse at a older age, had more positive attitudes toward abstinence, and more negative attitudes towardcondoms and discussion of safer sex. Implications for health education research and practice are discussed.

Combining HIV and AIDS surveillance: an experience from an Italian region.

Surveillance systems based on the reporting of AIDS cases do not provide a completely up to date picture of the trend of the HIV epidemic, stressing the need for systems based on the diagnosis of HIV infection. However, implementation of these systems has been hindered by low feasibility, poor access to HIV testing, and problems related to confidentiality. The advantages and disadvantages of the two systems and of combined use were explored by comparing and integrating information from AIDS and HIV testing registries in a region of Northern Italy. Linkage of AIDS and HIV testing registries allowed the annual number of incident and prevalent infections to be calculated. For linked cases, concordance of exposure category was determined. Up to the end of 1995, 2186 AIDS cases and 5306 HIV-positive individuals were diagnosed. Linkage identified 1212 individuals reported to both registries. From 1990 to 1995, annual AIDS incidence steadily increased, while incidence of new HIV diagnoses decreased. The AIDS-to-AIDS-free ratio among those infected decreased from 1:5.6 in 1989 to 1:4.2 in 1995. The proportion of women and noninjecting drug users was higher among AIDS-free cases than among AIDS cases. The concordance of the exposure category was high (K = 0.70; 95% CI: 0.67-0.74), but it varied by exposure category; the highest concordance was for injecting drug users. Integrated use of the information provided by these surveillance systems allowed us to better understand and foresee the AIDS epidemic dynamics. The data also suggested that the reliability of information on exposure category may vary among categories.

From the Centers for Disease Control and Prevention. Update: trends in AIDS incidence--United States, 1996

From the Centers for Disease Control and Prevention. Update: trends in AIDS incidence--United States, 1996

Update: Trends in AIDS Incidence—United States, 1996

Update: Trends in AIDS Incidence—United States, 1996

Projected incidence of AIDS in San Francisco: the peak and decline of the epidemic.

To predict the incidence of AIDS from 1978 through 1998 in San Francisco, we developed a model that combined annual HIV seroconversion rates for homosexual and bisexual men and for heterosexual injecting drug users with estimates of the incubation period distribution between HIV seroconversion and AIDS diagnosis and with estimates of the size of the at-risk populations. Our model assumed the availability of antiretroviral therapy at the efficacy level of zidovudine monotherapy. The annual number of new AIDS cases is estimated to have peaked at 3332 in 1992, and is projected to decline to 1196 annually by 1998. Although the projected number of cases decreased steadily during this period for homosexual and bisexual men, the projected number of cases for injection drug users, women, and persons with other risks increased between 1993 and 1998. The decline in the incidence of AIDS in San Francisco reflects the dramatic reductions in new HIV infections that occurred a decade previously and that were achieved as a result of significant changes in high-risk behaviors, primarily among homosexual and bisexual men. Changes in HIV seroincidence must be factored in before attributing the decrease in AIDS incidence to more effective combination antiretroviral treatment.

Changes in AIDS incidence for men who have sex with men, United States 1990-1995.

To describe changes in AIDS incidence for men who have sex with men (MSM) from 1990 to 1995, by demographic and geographic groups. We examined national AIDS surveillance data reported up to 30 September 1996, for men who received AIDS diagnoses in the years 1990-1995 and whose only reported risk behavior was sex with men. We evaluated trends in AIDS rates by estimating the incidence of clinical AIDS (AIDS defined by opportunistic illnesses), and report clinical AIDS incidence rates for MSM (AIDS rates) and proportional change in rates from 1990 to 1995. Clinical AIDS rates (MSM per 100,000 men per year) increased by 12% from 25.5% in 1990 to 28.5% in 1995. Significant variations in AIDS rates and 5-year changes in AIDS rates were observed in various subgroups of MSM. Five-year increases in AIDS rates were highest for American-Indian/Alaskan native (53%), black (45%), and Hispanic (23%) MSM; the only decrease occurred for white MSM (-2%). Incidence for black MSM increased from twofold (in 1990) to threefold (in 1995) the rate for white MSM. Large increases in AIDS rates were observed for MSM in rural areas (34%) and areas with 50,000 to 249,999 residents (34%) and for MSM aged over 60 years (32%). The high national AIDS rate for MSM continued to rise, but more slowly than earlier in the epidemic. Racial/ethnic minority MSM had consistently large increases in AIDS rates; AIDS rates decreased only slightly for white MSM. The AIDS epidemic among MSM is not homogenous, and AIDS rates continue to increase for minority MSM, and MSM living in rural areas. HIV prevention remains a high priority for all MSM, especially black and Hispanic MSM.

A Markov model for HIV disease progression including the effect of HIV diagnosis and treatment: application to AIDS prediction in England and Wales.

Back-calculation is a widely used method to estimate HIV incidence rates, and is commonly based on times of AIDS diagnosis. Following up earlier work, we extend this method to also incorporate knowledge of times of HIV diagnosis (first positive test). This is achieved through the use of a Markov model which describes the progress of an HIV infected person through various stages, and which allows causal connections between events to be explicitly modelled. Estimation is based on maximum likelihood, the likelihood being calculated within a discretized version of the Markov model. The effect of sampling uncertainty and model uncertainty (sensitivity) is evaluated simultaneously by means of a combined bootstrap and simulation procedure. At each replication we resample both the data and the model (from a set of possible models described by randomizing one or more parameters). For instance, uncertain knowledge about the incubation distribution affects the estimates of some parameters, but not others. The Markov approach is applied to the prediction of AIDS incidence for homosexuals in England and Wales up to the year 2000.

Estimating the number of AIDS-defining opportunistic illness diagnoses from data collected under the 1993 AIDS surveillance definition.

Expansion of the surveillance definition for AIDS in the United States in 1993 caused a substantial distortion in the trend in AIDS incidence, mainly because CD4-positive (CD4+) T-lymphocyte criteria were added to the definition. To evaluate trends in the rate at which HIV-infected persons develop the opportunistic illnesses listed in the AIDS surveillance definition (AIDS-OIs), we developed a procedure for estimating the incidence of these diseases. This estimate is based primarily on the probability distributions of the time from a CD4+ count in given ranges to the diagnosis of the first AIDS-OI. Our estimates of AIDS-OI incidence change by <4% during most calendar quarters during 1991 through 1995 if we also include the estimated effects of unreported AIDS-OIs among persons with AIDS reported based on the CD4+ criteria. Our procedure eliminates the transient effect of adding the CD4+ criteria to the AIDS surveillance definition and permits us to evaluate trends in the incidence of AIDS-OIs.

Whose blood is safer? The effect of the stage of the epidemic on screening for HIV.

With improvements in HIV antibody test (ELISA) performance, the window of time between infection and seroconversion becomes a major source of error in HIV screening. The authors examined its impact on the false-reassurance rate (FRR). Test sensitivity was modeled as the product of two factors: the inherent sensitivity (sensitivity when antibody is present) and the probability that antibody is present in infected blood. A model of HIV and AIDS incidence was used to derive an estimate of the probability of remaining in the seronegative window (pw) among those who are infected. With plausible assumptions, this probability approaches 0.03. The FRR was then estimated as a function of the probability of remaining in the seronegative window, the prevalence of HIV, and the inherent sensitivity of the ELISA test were estimated. The FRRs for two blood donor groups, one with an HIV prevalence of 0.004 and a typical probability of remaining in the seronegative window (pw = 0.03) and the other with a higher prevalence of 0.017 but fewer donors in the window (pw = 0.003), are equal (140 per million donors) if the blood is negative on a single ELISA test. After two negative tests or a single test that can detect antibody more reliably, however, the FRR is much higher in the group with the higher pw (= 120 per million compared with 50 per million), because the greater numbers of donors in the window more than offsets the lower prevalence. With improvements in inherent sensitivity of ELISA by virtue of technical progress or retesting, the prevalence of HIV infection may no longer play the critical role in degrading the results of blood screening. As inherent test performance improves, tests are increasingly likely to miss infected blood because of the seronegative-window error rather than because of measurement error. Window error plays a proportionally greater role during the early stages of HIV dissemination in a population where the incidence of new HIV infection is high relative to the incidence of AIDS. These findings may explain, in part, the recent observation that cases of transfusion of contaminated blood often take place in areas where AIDS epidemics have started recently. They also suggest that the traditional strategy of soliciting blood donors from low-prevalence populations may not always be optimal, unless such populations are truly low-risk.

Estimating and Projecting Regional HIV/AIDS Cases and Costs, 1990–2000: A Case Study

We developed predictions of HIV/AIDS caseloads and costs for the Northern Virginia Planning District Commission as input to its continuing evaluation of the economic welfare of northern Virginia's cities and counties. We developed a series of procedures beginning with US case and cost estimates for the period 1990 to 2000 and leading to estimates of state and local HIV/AIDS cases and costs. As a result, we estimate that the annual incidence of AIDS in northern Virginia will increase from 391 in 1990 to 643 by 2000, while pre-AIDS prevalence will decline from a peak of about 6,900 in 1993 to about 4,400 in 2000. We estimate the medical costs to the region of AIDS (excluding pre-AIDS cases) will reach $65 million annually (1992 $) by the turn of the century.