Increasing Capacity to Detect Clusters of Rapid HIV Transmission in Varied Populations—United States

Abstract

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.

HIV Cluster and Outbreak Detection and Response: The Science and Experience

“…54 Response efforts should be scaled to the size and characteristics of the cluster or outbreak and the needs of the transmission network. Although large outbreak responses are often highly visible, 55 CDR also includes intervening in the many clusters detected while still small, 13 which can most effectively limit transmission. 17,23 Therefore, CDR spans routine, day-today efforts to identify and prioritize clusters; initial response to small clusters; and expanded or escalated response to more concerning clusters and outbreaks (Figure 1).…”

“…Analysis by race/ethnicity and transmission category shows that groups experiencing rapid transmission do not necessarily mirror those with higher numbers of diagnoses and that these groups change over time and show substantial geographic variation. 13 Therefore, ongoing, routine analysis by HDs is necessary to identify the networks experiencing rapid transmission. By identifying these networks that are not being effectively reached by existing HIV prevention services, such ongoing analysis presents a vital opportunity to address health equity.…”

“…However, sexual transmission is the predominant mode of HIV transmission in the U.S. and in molecular clusters of rapid transmission. 13,35,57 Although responses to clusters and outbreaks related to sexual transmission have occurred, 6,7,9,10,19,24,28,32,34,36,37,58,59 these responses often do not garner as much attention or resources as do outbreaks among PWID and have not frequently been described in the literature. Using diverse methods to identify clusters in a variety of populations is important to build support for addressing gaps in services affecting networks experiencing rapid transmission regardless of the mode of transmission.…”

“…5−11 Beginning in 2018, CDC required all CDCfunded HDs to detect and respond to HIV clusters. 12 Although HDs are in varying phases of implementing this work, capacity for CDR has increased substantially in the U.S. 13 The Ending the HIV Epidemic initiative provides additional funding to HDs to strategically advance HIV prevention, including, for the Respond pillar, to implement innovative approaches to rapidly detect and respond to clusters and outbreaks. 14…”

Phylogenetic Insights on Patterns of HIV-1 Spread and the Design of Epidemic Control Measures

“…Cluster sizes and transmission rates were significantly higher for PWID than MSM, emphasizing the importance of targeted interventions to avert large outbreaks related to drug use. Notably, Oster et al showed that epidemics among PWID in the US states are also on the rise, comprising 1% and 11% of clustered infections in 2015-2016 and 2018-2019, respectively [7].…”