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Detecting and responding to clusters of rapid HIV transmission is a core HIV prevention strategy in the United States, guiding public health interventions and identifying gaps in prevention and care services. In 2016, the Centers for Disease Control and Prevention (CDC) initiated molecular cluster detection using data from 27 jurisdictions. During 2016-2023, CDC expanded sequence reporting nationwide and deployed Secure HIV-TRACE, an application supporting health department (HD) molecular cluster detection. CDC conducts molecular cluster detection quarterly; state and local HDs analyze local data monthly. HDs began routinely reporting clusters to CDC by using cluster report forms in 2020. During 2018-2023, CDC identified 404 molecular clusters of rapid HIV transmission; 325 (80%) involved multiple jurisdictions. During 2020-2023, HDs reported 298 molecular clusters to CDC; 249 were first detected by HDs. Expanding molecular cluster detection has provided a foundation for improving service delivery to networks experiencing rapid HIV transmission.

Molecular cluster detection analyzes HIV sequences to identify rapid HIV transmission and inform public health responses. We describe changes in the capability to detect molecular clusters and in geographic variation in transmission dynamics. We examined the reporting completeness of HIV-1 polymerase sequences in quarterly National HIV Surveillance System datasets from December 2015 to December 2019. Priority clusters were identified quarterly. To understand populations recently affected by rapid transmission, we described the transmission risk and race/ethnicity of people in clusters first detected in 2018–2019. During December 2015 to December 2019, national sequence completeness increased from 26% to 45%. Of the 1212 people in the 136 clusters first detected in 2018–2019, 69% were men who have sex with men (MSM) and 11% were people who inject drugs (PWID). State-by-state analysis showed substantial variation in transmission risk and racial/ethnic groups in clusters of rapid transmission. HIV sequence reporting has increased nationwide. Molecular cluster analysis identifies rapid transmission in varied populations and identifies emerging patterns of rapid transmission in specific population groups, such as PWID, who, in 2015–2016, comprised only 1% of people in such molecular clusters. These data can guide efforts to focus, tailor, and scale up prevention and care services for these populations.

Most sexually active people will be infected with a sexually transmitted infection (STI) at some point in their lives. The number of STIs in the United States was previously estimated in 2000. We updated previous estimates to reflect the number of STIs for calendar year 2008. We reviewed available data and literature and conservatively estimated incident and prevalent infections nationally for 8 common STIs: chlamydia, gonorrhea, syphilis, herpes, human papillomavirus, hepatitis B, HIV, and trichomoniasis. Where available, data from nationally representative surveys such as the National Health and Nutrition Examination Survey were used to provide national estimates of STI prevalence or incidence. The strength of each estimate was rated good, fair, or poor, according to the quality of the evidence. In 2008, there were an estimated 110 million prevalent STIs among women and men in the United States. Of these, more than 20% of infections (22.1 million) were among women and men aged 15 to 24 years. Approximately 19.7 million incident infections occurred in the United States in 2008; nearly 50% (9.8 million) were acquired by young women and men aged 15 to 24 years. Human papillomavirus infections, many of which are asymptomatic and do not cause disease, accounted for most of both prevalent and incident infections. Sexually transmitted infections are common in the United States, with a disproportionate burden among young adolescents and adults. Public health efforts to address STIs should focus on prevention among at-risk populations to reduce the number and impact of STIs.

The burden of HIV disease in the United States is monitored by using a com-prehensive surveillance system. Data from this system are used at the federal, state, and local levels to plan, implement, and evaluate public health policies and programs. Implementation of HIV reporting has differed by area, and for the first time in early 2013, estimated data on diagnosed HIV infection were available from all 50 states, the District of Columbia, and six U.S. dependent areas. The newly available data for the entire U.S. as well as several other key changes to the surveillance system support the need to provide an updated summary of the status of the National HIV Surveillance System.

CONTEXT HIV incidence is increasing among 13–24‐year‐old U.S. men who have sex with men, yet limited research is available to guide HIV prevention efforts for this population. METHODS National Survey of Family Growth data collected in 2002, in 2006–2010 and in 2011–2013 from 8,068 males aged 15–24 were analyzed to describe the population of U.S. young sexual minority males (i.e., males reporting same‐sex attraction, identity or behavior). Correlates of sexual minority classification were assessed in logistic regression models. RESULTS An estimated 10% of young males, representing a population of 2.1 million, were sexual minorities. Males had an elevated likelihood of being sexual minorities if they were aged 18–19 or 20–24, rather than 15–17 (prevalence ratio, 1.7 for each); belonged to nonblack, non‐Hispanic racial or ethnic minority groups (1.6); had no religious affiliation, rather than considering religion very important (1.9); or lived below the federal poverty level (1.3). They had a reduced likelihood of being sexual minorities if they lived in metropolitan areas outside of central cities (0.7). Among young sexual minority males, 44% were 15–19 years old, 29% were poor and 59% resided outside central cities. Forty‐seven percent had engaged in same‐sex behavior. Of those with data on all measured dimensions of sexuality, 24% reported same‐sex attraction, identity and behavior; 22% considered themselves heterosexual, yet had had a male sex partner. CONCLUSION Future investigations can further explore subpopulations of young sexual minority males and assess sexual trajectories, resilience and HIV risk.

In 2014, persons aged 13-29 years represented 23% of the U.S. population, yet accounted for 40% of diagnoses of human immunodeficiency virus (HIV) infection during the same year (1). During 2010-2014, the rates of diagnosis of HIV infection decreased among persons aged 15-19 years, were stable among persons aged 20-24 years, and increased among persons aged 25-29 years (1). However, these 5-year age groups encompass multiple developmental stages and potentially mask trends associated with the rapid psychosocial changes during adolescence through young adulthood. To better understand HIV infection among adolescents aged 13-17 years and young adults aged 18-29 years in the United States and identify ideal ages to target primary HIV prevention efforts, CDC analyzed data from the National HIV Surveillance System (NHSS)* using narrow age groups. During 2010-2014, rates of diagnosis of HIV infection per 100,000 population varied substantially among persons aged 13-15 years (0.7), 16-17 years (4.5), 18-19 years (16.5), and 20-21 years (28.6), and were higher, but less variable, among persons aged 22-23 years (34.0), 24-25 years (33.8), 26-27 years (31.3), and 28-29 years (28.7). In light of the remarkable increase in rates between ages 16-17, 18-19, and 20-21 years, and a recent study revealing that infection precedes diagnosis for young persons by an average of 2.7 years (2), these findings demonstrate the importance of targeting primary prevention efforts to persons aged <18 years and continuing through the period of elevated risk in their mid-twenties.

Public health interviews (i.e., partner services), during which persons with diagnosed human immunodeficiency virus (HIV) infection name their sexual or needle-sharing partners (named partners), are used to identify HIV transmission networks to guide and prioritize HIV prevention activities. HIV sequence data, generated from provider-ordered drug resistance testing, can be used to understand characteristics of molecular clusters, a group of sequences for which each sequence is highly similar (linked) to all other sequences, and assess whether named partners are plausible HIV transmission partners. Although molecular data in higher HIV-morbidity states have been analyzed (1-3), few analyses exist for lower morbidity states (4), such as Wisconsin, which reported 4.6 HIV diagnoses per 100,000 persons aged ≥13 years in 2016 (5). The Wisconsin Division of Public Health (DPH) analyzed HIV sequence data generated from provider-ordered drug resistance testing and collected through routine HIV surveillance to identify molecular clusters and describe demographic and transmission risk characteristics among pairs of persons whose sequences were highly genetically similar (i.e., molecular linkages). In addition, overlap between partner linkages identified during public health interviews and molecular linkages was assessed. Overall, characteristics of molecular clusters in Wisconsin mirrored those from states with more HIV diagnoses, particularly in that most molecular linkages were observed among persons of the same race (78.2% of non-Hispanic blacks [blacks] linked to other blacks), the same transmission risk (90.2% of men who have sex with men [MSM] linked to other MSM), and the same age group (59.2% of persons aged 20-29 years linked to other persons aged 20-29 years). Among named partner linkages identified during interviews in which both persons also had a reported sequence, overlap of named partner and molecular linkages was moderate: 33.8% of named partners were plausible transmission partners according to available molecular data. Analysis of HIV sequence data is a useful tool for characterizing transmission patterns not immediately apparent using traditional public health interview data, even in a state with lower HIV morbidity. Prevention recommendations generated from national data (e.g., targeting preexposure prophylaxis for HIV-negative persons at high risk and implementing measures to maintain viral suppression among persons with HIV infection) also are relevant in a lower HIV-morbidity state.

Identifying named partners through public health interviews is an important strategy for interrupting human immunodeficiency virus (HIV) transmission. Analyzing HIV molecular sequence data also can identify networks of potential transmission partners. Most molecular linkages in Wisconsin were among persons within the same racial/ethnic, risk, and age groups. Among named partner linkages where both persons had an HIV sequence available, 33.8% also had a molecular linkage and were deemed plausible transmission partners. Supplementing named partner data with molecular data might detect HIV transmission networks not elucidated through traditional public health interviews and identify opportunities for prevention in rapidly growing clusters of HIV infections in states with lower HIV morbidity.