BackgroundThe 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.MethodologyWe 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 FindingsEstimated 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/SignificanceOverall, 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.

Constructing scientifically sound samples of hard-to-reach populations, also known as hidden populations, is a challenge for many research projects. Traditional sample survey methods, such as random sampling from telephone or mailing lists, can yield low numbers of eligible respondents while non-probability sampling introduces unknown biases. The authors describe a venue-based application of time-space sampling (TSS) that addresses the challenges of accessing hard-to-reach populations. The method entails identifying days and times when the target population gathers at specific venues, constructing a sampling frame of venue, day-time units (VDTs), randomly selecting and visiting VDTs (the primary sampling units), and systematically intercepting and collecting information from consenting members of the target population. This allows researchers to construct a sample with known properties, make statistical inference to the larger population of venue visitors, and theorize about the introduction of biases that may limit generalization of results to the target population. The authors describe their use of TSS in the ongoing Community Intervention Trial for Youth (CITY) project to generate a systematic sample of young men who have sex with men. The project is an ongoing community level HIV prevention intervention trial funded by the Centers for Disease Control and Prevention. The TSS method is reproducible and can be adapted to hard-to-reach populations in other situations, environments, and cultures.

A theory-based multicomponent intervention (Gimme 5) was designed and implemented to impact fourth- and fifth-grade children's fruit, juice, and vegetable (FJV) consumption and related psychosocial variables. Gimme 5 was a randomized controlled intervention trial with school (n = 16 elementary) as unit of random assignment and analysis. Participants included the cohort of students who were in the third grade in the winter of 1994 and students who joined them in the fourth and fifth grades. The intervention included a curriculum, newsletters, videotapes, and point-of-purchase education. Evaluation included 7-day food records and psychosocial measures from students, telephone interviews with parents, and observational assessments. Favorable results were observed for consumption of FJV combined, FJV consumed at weekday lunch, eating FJV self-efficacy, social norms, asking behaviors, and knowledge. A theory-based school nutrition education program can help change children's FJV consumption and impact factors at home that predispose to FJV consumption, but changes were small, and their persistence is unknown.

Environmental variables can enable or impede children concerning what foods they consume. Availability and accessibility of foods are potentially important environmental variables. Availability concerns whether the foods are present in the home or school, while accessibility concerns whether the foods are prepared, presented, andor maintained in a form that enables or encourages children to eat them. We hypothesized that greater availability and accessibility would lead to more consumption. Baseline data from two school nutrition education projects were used to examine relationships between availabilitylaccessibility and consumption offruits and vegetables. In one study, children's consumption of fruits and vegetables (from seven day food records) was related to home availability and accessibility (as assessed by a parent telephone interview), after controlling for psychosocial characteristics. In the second study, children ate more fruits and vegetables for lunch at schools that offered more fruits and vegetables for lunch, after controlling for socioeconomic status. These results offer preliminary support for the hypothesized relationships. Future research must delineate the anticipated complex relationships among food purchase and preparation practices that lead to availability and accessibility, child and parent food preferences, and consumption, in order to more clearly guide interventions.