Amy Lansky

Estimated HIV Incidence in the United States, 2006–2009

Background The estimated number of new HIV infections in the United States reflects the leading edge of the epidemic. Previously, CDC estimated HIV incidence in the United States in 2006 as 56,300 (95% CI: 48,200–64,500). We updated the 2006 estimate and calculated incidence for 2007–2009 using improved methodology. Methodology We estimated incidence using incidence surveillance data from 16 states and 2 cities and a modification of our previously described stratified extrapolation method based on a sample survey approach with multiple imputation, stratification, and extrapolation to account for missing data and heterogeneity of HIV testing behavior among population groups. Principal Findings Estimated HIV incidence among persons aged 13 years and older was 48,600 (95% CI: 42,400–54,700) in 2006, 56,000 (95% CI: 49,100–62,900) in 2007, 47,800 (95% CI: 41,800–53,800) in 2008 and 48,100 (95% CI: 42,200–54,000) in 2009. From 2006 to 2009 incidence did not change significantly overall or among specific race/ethnicity or risk groups. However, there was a 21% (95% CI:1.9%–39.8%; p = 0.017) increase in incidence for people aged 13–29 years, driven by a 34% (95% CI: 8.4%–60.4%) increase in young men who have sex with men (MSM). There was a 48% increase among young black/African American MSM (12.3%–83.0%; p<0.001). Among people aged 13–29, only MSM experienced significant increases in incidence, and among 13–29 year-old MSM, incidence increased significantly among young, black/African American MSM. In 2009, MSM accounted for 61% of new infections, heterosexual contact 27%, injection drug use (IDU) 9%, and MSM/IDU 3%. Conclusions/Significance Overall, HIV incidence in the United States was relatively stable 2006–2009; however, among young MSM, particularly black/African American MSM, incidence increased. HIV continues to be a major public health burden, disproportionately affecting several populations in the United States, especially MSM and racial and ethnic minorities. Expanded, improved, and targeted prevention is necessary to reduce HIV incidence.

Surveillance of HIV risk and prevention behaviors of men who have sex with men : A national application of venue-based, time-space sampling

In collaboration with the Centers for Disease Control and Prevention, participating state and local health departments, universities, and community-based organizations applied venue-based, time-space sampling methods for the first wave of National HIV Behavioral Surveillance of men who have sex with men (NHBS-MSM). Conducted in 17 metropolitan areas in the United States and Puerto Rico from November 2003 through April 2005, NHBS-MSM methods included: (1) formative research to learn the venues, times, and methods to recruit MSM; (2) monthly sampling frames of eligible venues and day-time periods that met attendance, logistical, and safety criteria; and (3) recruitment of participants in accordance with randomly generated venue calendars. Participants were interviewed on HIV risk and prevention behaviors, referred to care when needed, and compensated for their time. By identifying the prevalence and trends of HIV risk and prevention behaviors, NHBS-MSM data may be used at local, state, and federal levels to help obtain, direct, and evaluate HIV prevention resources for MSM.

Human immunodeficiency virus transmission at each step of the care continuum in the United States.

IMPORTANCE Human immunodeficiency virus (HIV) transmission risk is primarily dependent on behavior (sexual and injection drug use) and HIV viral load. National goals emphasize maximizing coverage along the HIV care continuum, but the effect on HIV prevention is unknown. OBJECTIVES To estimate the rate and number of HIV transmissions attributable to persons at each of the following 5 HIV care continuum steps: HIV infected but undiagnosed, HIV diagnosed but not retained in medical care, retained in care but not prescribed antiretroviral therapy, prescribed antiretroviral therapy but not virally suppressed, and virally suppressed. DESIGN, SETTING, AND PARTICIPANTS A multistep, static, deterministic model that combined population denominator data from the National HIV Surveillance System with detailed clinical and behavioral data from the National HIV Behavioral Surveillance System and the Medical Monitoring Project to estimate the rate and number of transmissions along the care continuum. This analysis was conducted January 2013 to June 2014. The findings reflect the HIV-infected population in the United States in 2009. MAIN OUTCOMES AND MEASURES Estimated rate and number of HIV transmissions. RESULTS Of the estimated 1,148,200 persons living with HIV in 2009, there were 207,600 (18.1%) who were undiagnosed, 519,414 (45.2%) were aware of their infection but not retained in care, 47,453 (4.1%) were retained in care but not prescribed ART, 82,809 (7.2%) were prescribed ART but not virally suppressed, and 290,924 (25.3%) were virally suppressed. Persons who are HIV infected but undiagnosed (18.1% of the total HIV-infected population) and persons who are HIV diagnosed but not retained in medical care (45.2% of the population) were responsible for 91.5% (30.2% and 61.3%, respectively) of the estimated 45,000 HIV transmissions in 2009. Compared with persons who are HIV infected but undiagnosed (6.6 transmissions per 100 person-years), persons who were HIV diagnosed and not retained in medical care were 19.0% (5.3 transmissions per 100 person-years) less likely to transmit HIV, and persons who were virally suppressed were 94.0% (0.4 transmissions per 100 person-years) less likely to transmit HIV. Men, those who acquired HIV via male-to-male sexual contact, and persons 35 to 44 years old were responsible for the most HIV transmissions by sex, HIV acquisition risk category, and age group, respectively. CONCLUSIONS AND RELEVANCE Sequential steps along the HIV care continuum were associated with reduced HIV transmission rates. Improvements in HIV diagnosis and retention in care, as well as reductions in sexual and drug use risk behavior, primarily for persons undiagnosed and not receiving antiretroviral therapy, would have a substantial effect on HIV transmission in the United States.

Estimating per-act HIV transmission risk: a systematic review

Background:Effective HIV prevention programs rely on accurate estimates of the per-act risk of HIV acquisition from sexual and parenteral exposures. We updated the previous risk estimates of HIV acquisition from parenteral, vertical, and sexual exposures, and assessed the modifying effects of factors including condom use, male circumcision, and antiretroviral therapy. Methods:We conducted literature searches to identify new studies reporting data regarding per-act HIV transmission risk and modifying factors. Of the 7339 abstracts potentially related to per-act HIV transmission risk, three meta-analyses provided pooled per-act transmission risk probabilities and two studies provided data on modifying factors. Of the 8119 abstracts related to modifying factors, 15 relevant articles, including three meta-analyses, were included. We used fixed-effects inverse-variance models on the logarithmic scale to obtain updated estimates of certain transmission risks using data from primary studies, and employed Poisson regression to calculate relative risks with exact 95% confidence intervals for certain modifying factors. Results:Risk of HIV transmission was greatest for blood transfusion, followed by vertical exposure, sexual exposures, and other parenteral exposures. Sexual exposure risks ranged from low for oral sex to 138 infections per 10 000 exposures for receptive anal intercourse. Estimated risks of HIV acquisition from sexual exposure were attenuated by 99.2% with the dual use of condoms and antiretroviral treatment of the HIV-infected partner. Conclusion:The risk of HIV acquisition varied widely, and the estimates for receptive anal intercourse increased compared with previous estimates. The risk associated with sexual intercourse was reduced most substantially by the combined use of condoms and antiretroviral treatment of HIV-infected partners.

Estimating the Population Size of Men Who Have Sex with Men in the United States to Obtain HIV and Syphilis Rates

Background: CDC has not previously calculated disease rates for men who have sex with men (MSM) because there is no single comprehensive source of data on population size. To inform prevention planning, CDC developed a national population size estimate for MSM to calculate disease metrics for HIV and syphilis. Methods: We conducted a systematic literature search and identified seven surveys that provided data on same-sex behavior in nationally representative samples. Data were pooled by three recall periods and combined using meta-analytic procedures. We applied the proportion of men reporting same-sex behavior in the past 5 years to U.S. census data to produce a population size estimate. We then calculated three disease metrics using CDC HIV and STD surveillance data and rate ratios comparing MSM to other men and to women. Results: Estimates of the proportion of men who engaged in same-sex behavior differed by recall period: past year = 2.9% (95%CI, 2.6–3.2); past five years = 3.9% (3.5–4.4); ever = 6.9% (5.1–8.6). Rates on all 3 disease metrics were much higher among MSM than among either other men or women (38 to 109 times as high). Conclusions: Estimating the population size for MSM allowed us to calculate rates for disease metrics and to develop rate ratios showing dramatically higher rates among MSM than among other men or women. These data greatly improve our understanding of the disproportionate impact of these diseases among MSM in the U.S. and help with prevention planning.

Behavioral Surveillance Among People at Risk for HIV Infection in the U.S.: The National HIV Behavioral Surveillance System

The Centers for Disease Control and Prevention, in collaboration with 25 state and local health departments, began the National HIV Behavioral Surveillance System (NHBS) in 2003. The system focuses on people at risk for HIV infection and surveys the three populations at highest risk for HIV in the United States: men who have sex with men, injecting drug users, and high-risk heterosexuals. The project collects information from these three populations during rotating 12-month cycles. Methods for recruiting participants vary for each at-risk population, but NHBS uses a standardized protocol and core questionnaire for each cycle. Participating health departments tailor their questionnaire to collect information about specific prevention programs offered in their geographic area and to address local data needs. Data collected from NHBS will be used to describe trends in key behavioral risk indicators and evaluate current HIV prevention programs. This information in turn can be used to identify gaps in prevention services and target new prevention activities with the goal of reducing new HIV infections in the United States.

HIV testing within at-risk populations in the United States and the reasons for seeking or avoiding HIV testing.

Objectives: We determined proportions of high‐risk persons tested for HIV, the reasons for testing and not testing, and attitudes and perceptions regarding HIV testing, information that is critical for planning prevention programs. Methods: Cross‐sectional interview study of persons at high risk for HIV infection (men who have sex with men [MSM]; injection drug users [IDUs]; and heterosexual persons recruited from gay bars, street outreach, and sexually transmitted disease clinics) among six states participating in the HIV Testing Survey (HITS) in 1995 to 1996 (HITS‐I) and 1998 to 1999 (HITS‐II). Results: Overall testing rates were lower in the HITS‐I (1226/1599 [77%]) than in the HITS‐II (1375/1711 [80%]) (p = .01). Persons <25 years old tested less frequently than those >25 years old (HITS‐I: 71 % vs. 78%, respectively, p = .007; HITS‐II: 63% vs. 85%, respectively, p < .001). The main reasons for testing and not testing were the same in both surveys, but the proportions of reasons for not testing differed (e.g., “unlikely exposed to HIV” [HITS‐I (17%) vs. HITS‐II (30%), p < .0001], “afraid of finding out HIV‐positive” [HITS‐I (27%) vs. HITS‐II (18%), p < .0001]). Attitudes regarding HIV testing differed among tested and untested respondents, especially among MSM. Conclusions: HIV testing rates were higher in the HITS‐II, but testing rates decreased among the youngest respondents. Denial of HIV risk factors and fear of being HIV‐positive were the principal reasons for not being tested. Availability of new HIV therapies may have contributed to decreased fear of finding out that one is HIV infected as a reason to avoid testing. The increased proportion of persons at risk who did not test because they believed they were unlikely to have been exposed highlights the need for prevention efforts to address risk perceptions.

The Pregnancy Risk Assessment Monitoring System (PRAMS): Current Methods and Evaluation of 2001 Response Rates

Objectives. Our objectives were to describe the methodology of the Pregnancy Risk Assessment Monitoring System (PRAMS), examine recent response rates, determine characteristics associated with response, and track response patterns over time. Methods. PRAMS is a mixed-mode surveillance system, using mail and telephone surveys. Rates for response, contact, cooperation, and refusal were computed for 2001. Logistic regression was used to examine the relationship between maternal and infant characteristics and the likelihood of response. Response patterns from 1996 to 2001 were compared for nine states. Results. The median response rate for the 23 states in 2001 was 76% (range: 49% to 84%). Cooperation rates ranged from 86% to 97% (median 91%); contact rates ranged from 58% to 93% (median 82%). Response rates were higher for women who were older, white, married, had more education, were first-time mothers, received early prenatal care, and had a normal birthweight infant. Education level was the most consistent predictor of response, followed by marital status and maternal race. From 1996 to 2001, response to the initial mailing decreased in all states compared, but the decrease was offset by increases in mail follow-up and telephone response rates. Overall response rates remained unchanged. Conclusions. The PRAMS mail/telephone methodology is an effective means of reaching most recent mothers in the 23 states examined, but some population subgroups are more difficult to reach than others. Through more intensive follow-up efforts, PRAMS states have been able to maintain high response rates over time despite decreases in response to the initial mailing.

Developing an HIV Behavioral Surveillance System for Injecting Drug Users: The National HIV Behavioral Surveillance System

While disease surveillance for HIV/AIDS is now widely conducted in the United States, effective HIV prevention programs rely primarily on changing behavior; therefore, behavioral data are needed to inform these programs. To achieve the goal of reducing HIV infections in the U.S., the Centers for Disease Control and Prevention, in cooperation with state and local health departments, implemented the National HIV Behavioral Surveillance System (NHBS) for injecting drug users (IDUs) in 25 selected metropolitan statistical areas (MSAs) throughout the United States in 2005. The surveillance system used respondent-driven sampling (RDS), a modified chain-referral method, to recruit IDUs for a survey measuring HIV-associated drug use and sexual risk behavior. RDS can produce population estimates for specific risk behaviors and demographic characteristics. Formative assessment activities—primarily the collection of qualitative data—provided information to better understand the IDU population and implement the surveillance activities in each city. This is the first behavioral surveillance system of its kind in the U.S. that will provide local and national data on risk for HIV and other blood-borne and sexually transmitted infections among IDUs for monitoring changes in the epidemic and prevention programs.

Reasons for not HIV testing, testing intentions, and potential use of an over-the-counter rapid HIV test in an internet sample of men who have sex with men who have never tested for HIV.

Background: Correlates of main reasons for not HIV testing, HIV testing intentions, and potential use of an over-the-counter rapid HIV test (OTCRT) among men who have sex with men who have never tested for HIV (NTMSM) are unknown. Methods: We evaluated these correlates among 946 NTMSM from 6 US cities who participated in an internet-based survey in 2007. Findings: Main reasons for not testing were low perceived risk (32.2%), structural barriers (25.1%), and fear of testing positive (18.1%). Low perceived risk was associated with having fewer unprotected anal intercourse (UAI) partners and less frequent use of the internet for HIV information; structural barriers were associated with younger age and more UAI partners; fear of testing positive was associated with black and Hispanic race/ethnicity, more UAI partners, and more frequent use of the internet for HIV information. Strong testing intentions were held by 25.9% of all NTMSM and 14.8% of those who did not test because of low perceived risk. Among NTMSM who were somewhat unlikely, somewhat likely, and very likely to test for HIV, 47.4%, 76.5%, and 85.6% would likely use an OTCRT if it was available, respectively. Conclusions: Among NTMSM who use the internet, main reasons for not testing for HIV vary considerably by age, race/ethnicity, UAI, and use of the internet for HIV information. To facilitate HIV testing of NTMSM, programs should expand interventions and services tailored to address this variation. If approved, OTCRT might be used by many NTMSM who might not otherwise test for HIV.