A model-based estimate of the mean incubation period for AIDS in homosexual men.

Because of the difficulty in identifying the date of exposure to type 1 of the human immunodeficiency virus (HIV-1) infection in persons other than transfusion recipients, studies of the incubation periods for acquired immunodeficiency syndrome (AIDS) have been limited. When data from a cohort of 84 homosexual and bisexual men that provided the information to determine the years of conversion of sera infected with HIV-1 were analyzed, a model for the proportion likely to develop AIDS and the incubation period for AIDS in homosexual men could be derived. The maximum likelihood estimate for the proportion of infected homosexual men developing AIDS is 0.99 (90% confidence interval ranging from 0.38 to 1). Furthermore, the maximum likelihood estimate for the mean incubation period for AIDS in homosexual men is 7.8 years (90% confidence interval ranging from 4.2 years to 15.0 years), which is close to the estimate of 8.2 years for adults developing transfusion-associated AIDS.

The epidemiology of AIDS: current status and future prospects.

The reported incidence of acquired immune deficiency syndrome (AIDS) continues to increase in countries throughout the world. On the basis of a polynomial model for extrapolation, the cumulative number of cases diagnosed and reported since 1981 in the United States is expected to double during the next year with over 12,000 additional cases projected to be diagnosed by July 1986. The annual incidence rates for single (never-married) men in Manhattan and San Francisco, intravenous drug users in New York City and New Jersey, and persons with hemophilia A ranged from 261 to 350 per 100,000 population during 1984. For single men aged 25 to 44 years in Manhattan and San Francisco, AIDS was the leading cause of premature mortality in 1984 as measured by years of potential life lost. Infection with HTLV-III/LAV is considerably more common than reported AIDS in high-risk populations and can persist at least for several years, so the presence of specific antibody should be considered presumptive evidence of current infection. The screening of donated blood and plasma for antibody to HTLV-III/LAV and use of safer clotting factor concentrates should greatly reduce HTLV-III/LAV transmission through blood and blood products. Most HTLV-III/LAV infections occur through sexual transmission, use of contaminated needles, and as a result of infected mothers passing the virus to newborns. Continued research commitment is needed to develop an HTLV-III/LAV vaccine and therapy for this infection. In the interim, widespread community efforts are needed to minimize transmission.

Intravenous drug abusers and the acquired immunodeficiency syndrome (AIDS). Demographic, drug use, and needle-sharing patterns.

We studied the demographic characteristics, drug use patterns, and sexual habits of intravenous (IV) drug abusers to further define this population at risk for acquired immunodeficiency syndrome (AIDS). Sixteen IV drug abuser patients with AIDS, 24 IV drug abuser patients with AIDS-related complex (ARC), and 14 IV drug abuser controls without evidence of AIDS or ARC were evaluated. The subjects in each group were similar demographically, in drug use practice, and in sexual orientation and experience. Of the AIDS and ARC patients, 34 (88%) of 40, including all seven homosexual men, shared needles, as did all drug abusers without AIDS or ARC. Seventy-four percent of patients, including all homosexual men, attended "shooting galleries," where anonymous multiple-partner needle sharing took place. Needle sharing supports the hypothesis of AIDS transmission by a blood-borne route, can explain the spread of AIDS and the high rate of seropositivity to the putative AIDS agent among IV drug abusers, and is a logical link between IV drug abusers and male homosexuals, the two largest groups with AIDS.

Willingness to participate in a national seroprevalence study of HIV infection.

This paper examines the impact of the social dimension of AIDS on a person's willingness to participate in a hypothetical national seroprevalence study of HIV infection. Data from the AIDS supplement of the 1987 National Health Interview Survey provided information about the sociodemographic characteristics and AIDS-related variables and the expressed willingness to participate in a national serosurvey. A multivariate logistic regression model was used to evaluate simultaneously associations between the sociodemographic variables and AIDS-related variables with willingness to participate. Results show that those with sociodemographic characteristics most dissimilar from reported AIDS cases were least willing to participate while those with a high knowledge about AIDS, experience of the HIV test or tested people, and higher perceptions of risk were more willing to participate. We found two exceptions to this general result. First, respondents with no knowledge about AIDS, but a higher level of education, were less willing to participate than those with no knowledge and a lower level of education. Second, respondents with a higher perception of risk and a higher level of education were also less willing than those with high perception of risk and less education.

Estimating AIDS infection rates in the San Francisco cohort.

Between 1978 and 1980 a cohort of approximately 6700 homosexual and bisexual men were recruited from the San Francisco City Clinic to participate in studies of sexually transmitted hepatitis B. Testing frozen blood specimens collected at intervals from these patients provides a means of tracking the spread of the AIDS virus since 1978. The rate of spread of HIV was estimated by fitting different survival curves to interval-censored serological data using maximum likelihood techniques. The curves were compared using the Akaike Information Criterion (AIC) to select that which best describes the data. The best was found to be a log-logistic model, which suggested that between 1978 and 1981 the virus spread rapidly, infecting 44% of the then uninfected cohort members. More recently the rate of spread has declined, with an additional 32% of the cohort becoming infected between 1981 and 1987.

AIDS in Colorado Springs: is there an epidemic?

OBJECTIVE: To analyze trends and patterns of HIV infection in a medium-sized community in the United States. METHODS: Surveillance for AIDS and HIV infection was conducted by private physicians, military and public clinics, and blood and plasma donation centers. HIV-positive individuals were contacted and asked to refer their sex and injection partners for HIV-antibody testing. Prostitutes, injecting drug users and their sex partners were studied. Selected physicians were surveyed to assess under-reporting. RESULTS: The 740 HIV-infected adults (67 with documented seroconversion) included 506 with no evidence of AIDS, 58 living with AIDS, and 176 who had died. Of the 126 patients cared for by local physicians, 107 (85%) had been reported. No major changes in behavioral risk factors or increases in the number of HIV-infected individuals occurred between 1986 (128) and 1992 (95). CONCLUSIONS: Characteristics of individuals at risk and incidence of HIV infection have remained stable from 1981 to 1992. Analysis of data from the comprehensive surveillance and control program established in Colorado Springs in response to the AIDS epidemic suggests that, unlike the nation's epicenters, HIV incidence in this location is neither widespread nor rapidly increasing. The age distribution of reported cases is slowly increasing, and the ratio of newly reported cases to deaths is declining, implying stable or decreasing incidence; deaths may soon exceed new cases. Using data routinely available to public health officials, we conclude that the epidemiologic picture of AIDS--like the clinical one--must be heterogeneous, and that rational planning for the impact of AIDS should be based on the collection and analysis of local data.

Social network dynamics and HIV transmission.

OBJECTIVE: To prospectively study changes in the social networks of persons at presumably high risk for HIV in a community with low prevalence and little endogenous transmission. METHODS: From a cohort of 595 persons at high risk (prostitutes, injecting drug users, and sexual partners of these persons) and nearly 6000 identified contacts, we examined the social networks of a subset of 96 persons who were interviewed once per year for 3 years. We assessed their network configuration, network stability, and changes in risk configuration and risk behavior using epidemiologic and social network analysis, and visualization techniques. RESULTS: Some significant decrease in personal risk-taking was documented during the course of the study, particularly with regard to needle-sharing. The size and number of connected components (groups that are completely connected) declined. Microstructures (small subgroups of persons that interact intensely) were either not present, or declined appreciably during the period of observation. CONCLUSIONS: In this area of low prevalence, the lack of endogenous transmission of HIV may be related in part to the lack of a network structure that fosters active propagation, despite the continued presence of risky behaviors. Although the relative contribution of network structure and personal behavior cannot be ascertained from these data, the study suggests an important role for network configuration in the transmission dynamics of HIV.

Mapping a social network of heterosexuals at high risk for HIV infection.

OBJECTIVE: To determine how heterosexuals at risk for HIV infection interconnect in social networks and how such relationships affect HIV transmission. DESIGN: Cross-sectional study with face-to-face interviews to ascertain sociosexual connections; serologic testing. PARTICIPANTS: Prostitute women (n = 133), their paying (n = 129) and non-paying (n = 47) male partners; injecting drug users (n = 200) and their sex partners (n = 41). Participants were recruited in sexually transmitted disease and methadone clinics, an HIV-testing site, and through street outreach in Colorado Springs, Colorado, USA. MAIN OUTCOME MEASURES: Reported behaviors, risk perceptions, sociosexual linkages, and HIV prevalence. RESULTS: Respondents were well informed, but reported engaging in high-risk behaviors frequently. Nevertheless, over 70% of respondents perceived themselves to be at low risk for HIV infection. The 595 respondents identified a social network of 5162 people to which they belonged. Network analytic methods indicated 147 separate connected components of this network; eight of the 19 HIV-positive individuals in the network were located in smaller components remote from the largest connected component. CONCLUSION: The isolated position of HIV-positive individuals may serve as a barrier to HIV transmission and may account for the lack of diffusion of HIV in heterosexual populations in this region. Network analysis appears useful for understanding the dynamics of disease transmission and warrants further development as a tool for intervention and control.

Sexual behavior before AIDS: the hepatitis B studies of homosexual and bisexual men.

Data on sexual practices, collected during studies of hepatitis B virus (HBV) infection in 1978 and 1979, were analyzed for 4910 homosexual and bisexual men from Chicago, Denver, Los Angeles, San Francisco, and St Louis. Data on sexual practices in 1978 showed that white participants had larger numbers of non-steady male sexual partners and engaged in oral-genital activities more frequently but were equally likely to engage in anal intercourse as black and Hispanic participants. San Francisco participants had more non-steady sex partners and were more likely to engage in receptive anal intercourse with non-steady partners than participants from all other sites. Analysis of data on 606 HBV-antibody-negative men interviewed on three occasions in 1978 and 1979 showed no changes in risk indices for insertive and receptive anal intercourse between these years, except in San Francisco where significant declines occurred in insertive anal intercourse and receptive anal intercourse without ejacultion in a small, highly select group of participants.

Kaposi's sarcoma among homosexual and bisexual men enrolled in the San Francisco City Clinic Cohort Study.

The changing epidemiology of Kaposi's sarcoma (KS) and possible explanations for this change were analyzed using data from a well-characterized cohort of homosexual and bisexual men. Among 1,341 men with AIDS, the proportion presenting with KS declined from 79% in 1981 to 25% in 1989. For 250 men whose date of HIV seroconversion could be well characterized, persons presenting with KS had a shorter interval from HIV seroconversion to AIDS diagnosis than other AIDS patients without KS (mean = 77 vs. 86 months). Among 182 men who were interviewed prior to a diagnosis of AIDS, men with and without KS did not significantly differ with respect to number of sex partners, a history of certain sexually transmitted or enteric diseases, use of certain recreational drugs (including nitrite inhalants), or participation in certain specific sexual practices. The decline in KS may at least partly be due to a shorter latency period from infection to disease. Although cofactors for the development of KS may exist, many previously hypothesized agents were not supported by this analysis.

Cluster of cases of the acquired immune deficiency syndrome. Patients linked by sexual contact.

The possibility that homosexual men with the acquired immune deficiency syndrome (AIDS) had been sexual partners of each other was studied. Of the first 19 homosexual male AIDS patients reported from southern California, names of sexual partners were obtained for 13. Nine of the 13 patients had sexual contact with one or more AIDS patients within five years of the onset of symptoms. Four of the patients from southern California had contact with a non-Californian AIDS patient, who was also the sexual partner of four AIDS patients from New York City. Ultimately, 40 patients in 10 cities were linked by sexual contact. On the basis of six pairs of patients, a mean latency period of 10.5 months (range seven to 14 months) is estimated between sexual contact and symptom onset. The finding of a cluster of AIDS patients linked by sexual contact is consistent with the hypothesis that AIDS is caused by an infectious agent.

High-risk sexual behavior and knowledge of HIV antibody status in the San Francisco City Clinic Cohort.

To evaluate the effectiveness of human immunodeficiency virus (HIV) testing and counseling among homosexual and bisexual men participating in the San Francisco City Clinic Cohort, compared behavioral data from 181 men who learned their HIV antibody status between 1985 and 1987 with data from 128 men who were tested but declined to receive their results. Overall, significant declines in risk indices for unprotected receptive and insertive anal intercourse occurred between 1983-1984 and 1986-1987, but these declines were independent of both knowledge of HIV status and actual serostatus. Those who chose to learn their HIV status were also no more likely to report depression or to learn their HIV status were also no more likely to report depression or anxiety subsequent to testing. Regression analyses showed no relationship between length of time since learning one's HIV status, mental health symptoms, and the persistence of high-risk behavior in 1986-1987. Although these results do not negate the value of HIV testing and counseling, they suggest that other motivating factors such as frequent access to risk-reduction information may provide sufficient impetus for behavioral change.

Social networks and infectious disease: the Colorado Springs Study.

The social network paradigm provides a set of concepts and methods useful for studying the structure of a population through which infectious agents transmitted during close personal contact spread, and an opportunity to develop improved disease control programs. The research discussed was a first attempt to use a social network approach to better understand factors affecting the transmission of a variety of pathogens, including hepatitis B virus (HBV) and human immunodeficiency viruses (HIV), in a population of prostitutes, injecting drug users (IDU) and their personal associates in a moderate-sized city (Colorado Springs, CO). Some of the challenges of studying large social networks in epidemiological research are described, some initial results reported and a new view of interconnections in an at risk population provided. Overall, for the first time in epidemiologic research a large number of individuals (over 600) were found connected to each other, directly or indirectly, using a network design. The average distance (along observed social relationships) between persons infected with HIV and susceptible persons was about three steps (3.1) in the core network region. All susceptibles in the core were within seven steps of HIV infection.

Social and psychologic aspects of the sexually transmitted diseases: a different view.

A sociologic model is presented which interrelates four major variables: health providers, health consumers, the sociocultural environment, and social exchange. This model is proposed as an alternative to the prevailing medical model where the patient is pictured as a passive carrier who presents a problem to the competent physician to define, treat and control. In contrast to the epidemiologic model, the new model puts the health professional on the same level as the patient and demands that we take a critical look at our own values and behavior as well as that of the patient community. Studies are presented which indicate that in the United States there is much left to be desired in our performance as far as screening, diagnosis, treatment, reporting and follow-up of sexually transmitted diseases (STDs) are concerned. We have a tendency to dismiss the reasons for noncompliance of patients as "poor excuses" but we are probably even less compliant in doing what should be done to control STDs. Setting realistic goals and accepting the challenge of solving this problem are essential.

Course of HIV-I infection in a cohort of homosexual and bisexual men: an 11 year follow up study.

OBJECTIVE--To characterise the natural history of sexually transmitted HIV-I infection in homosexual and bisexual men. DESIGN--Cohort study. SETTING--San Francisco municipal sexually transmitted disease clinic. PATIENTS--Cohort included 6705 homosexual and bisexual men originally recruited from 1978 to 1980 for studies of sexually transmitted hepatitis B. This analysis is of 489 cohort members who were either HIV-I seropositive on entry into the cohort (n = 312) or seroconverted during the study period and had less than or equal to 24 months between the dates of their last seronegative and first seropositive specimens (n = 177). A subset of 442 of these men was examined in 1988 or 1989 or had been reported to have developed AIDS. MAIN OUTCOME MEASURES--Development of clinical signs and symptoms of HIV-I infection, including AIDS, AIDS related complex, asymptomatic generalised lymphadenopathy, and no signs or symptoms of infection. MEASUREMENTS AND MAIN RESULTS--Of the 422 men examined in 1988 or 1989 or reported as having AIDS, 341 had been infected from 1977 to 1980; 49% (167) of these men had died of AIDS, 10% (34) were alive with AIDS, 19% (65) had AIDS related complex, 3% (10) had asymptomatic generalised lymphadenopathy, and 19% (34) had no clinical signs or symptoms of HIV-I infection. Cumulative risk of AIDS by duration of HIV-I infection was analysed for all 489 men by the Kaplan-Meier method. Of these 489 men, 226 (46%) had been diagnosed as having AIDS. We estimated that 13% of cohort members will have developed AIDS within five years of seroconversion, 51% within 10 years, and 54% within 11.1 years. CONCLUSION--Our analysis confirming the importance of duration of infection to clinical state and the high risk of AIDS after infection underscores the importance of continuing efforts both to prevent transmission of HIV-I and to develop further treatments to slow or stall the progression of HIV-I infection to AIDS.