icon-    folder.gif   Conference Reports for NATAP  
  IAS 2017: Conference on HIV Pathogenesis
Treatment and Prevention
Paris, France
July 23-26 2017
Back grey_arrow_rt.gif
CDC Transmission Study Puts Hispanic MSM at Leading Edge of HIV Spread - Analysis of U.S. HIV sequence data indicates that recent and rapid HIV transmission is focused among young Hispanic/Latino men who have sex with men
  9th IAS Conference on HIV Science (IAS 2017), July 23-26, 2017, Paris
Mark Mascolini
Analysis of more than 30,000 HIV sequences from across the United States yielded evidence that HIV is spreading rapidly in Hispanic men who have sex with men (MSM), particularly Hispanic MSM under 30 years old [1]. The findings suggest Hispanic MSM represent "the leading edge of HIV transmission" in the country.
Estimated HIV transmission across the United States stands at about 4 transmissions per 100 person-years, according to CDC researchers who conducted the new study. But transmission rates probably exceed that estimate in certain populations. The CDC team conducted this analysis to home in on the leading edge of HIV's spread by identifying and characterizing molecular clusters with recent rapid growth.
The study involved HIV-1 polymerase sequences from 30,323 people diagnosed with HIV from 2013 through 2015 in 27 jurisdictions across the United States. To identify transmission clusters, the researchers calculated genetic distance for each pair of sequences using a pairwise threshold of 0.005 substitutions per site. They defined a rapidly growing transmission cluster as one with 5 or more transmissions during 2015. The team performed molecular clock phylogenetic analysis "to estimate time to most recent common ancestor and internal node ages, which we used as a proxy for transmission events."
This analysis turned up 13 rapidly growing clusters involving a median of 17 HIV transmissions (range 6 to 22). There were 196 people in these clusters, including 41% diagnosed in 2015 and 63% with recent infection. Molecular clock phylogenetic analysis determined that cluster age ranged from 1.8 to 9.2 years. Of 182 total transmissions, 23 (13%) occurred within 1 year.
Calculating transmission rate as number of transmissions in the cluster divided by total HIV-infected person time, the CDC team determined a transmission rate of 35 per 100 person-years in the 13 rapidly growing clusters. This rate exceeds the overall estimated US HIV transmission rate (4 per 100) by almost 9 times.
Next the investigators compared the 196 people in the 13 rapidly growing clusters with the 30,127 other people who contributed a sequence to the analysis. The rapid-cluster group included significantly higher proportions of 6 groups:
-- MSM (94% versus 62% of all others, P < 0.001)
-- Hispanic/Latino (49% versus 28%, P < 0.001)
-- Age under 30 at diagnosis (68% versus 41%, P < 0.001)
-- Under-30 MSM (63% versus 31%, P < 0.001)
-- Under-30 Hispanic/Latino MSM (32% versus 9%, P < 0.001)
-- Drug resistance-associated mutations (43% versus 20%, P = 0.006)
Blacks were significantly less likely to be in one of the 13 clusters (14% versus 40%, P = 0.001).
The CDC concluded that the rapidly growing clusters "likely reflect the leading edge of HIV transmission" in the United States, "where rapid transmission results in a disproportionate number of new HIV infections." The investigators called for enhanced prevention efforts targeting Hispanic MSM.
1. Oster AM, France AM, Panneer N, et al. Analysis of U.S. HIV sequence data indicates that recent and rapid HIV transmission is focused among young Hispanic/Latino men who have sex with men. 9th IAS Conference on HIV Science (IAS 2017), July 23-26, 2017, Paris. Abstract WEPDX0103.
Analysis of U.S. HIV sequence data indicates that recent and rapid HIV transmission is focused among young Hispanic/Latino men who have sex with men
Alexandra M. Oster, MD;1Anne Marie France,1Nivedha Panneer,1Joel O. Wertheim, 1,2M. Cheryl BanezOcfemia,1Sharoda Dasgupta,1Angela L. Hernandez1 1 Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, United States and 2 University of California, San Diego


Background: Although the estimated rate of HIV transmission in the United States is approximately 4 transmission events per 100 person-years, the rate of transmission in some risk networks is likely much higher. Identifying these networks can provide critical data for focusing efforts on populations in need of the most intensive prevention interventions. To describe the leading edge of HIV transmission, we identified molecular clusters with recent and rapid growth, determined the transmission rate for these clusters, and described the persons involved in rapid transmission.
Methods:: We analyzed baseline partial HIV-1 polymerase sequences reported to the National HIV Surveillance System through December 2015 by 27 participating jurisdictions for persons with HIV diagnosed during 2013-2015. We calculated genetic distance for each pair of sequences. Using a pairwise threshold of 0.005 substitutions/site, we inferred clusters and identified rapidly growing clusters (those with ≥5 diagnoses during 2015). We used node ages determined through molecular clock phylogenetic analysis to calculate HIV transmission rates for these rapidly growing clusters and compared persons in these clusters to other persons with sequences included in the analysis, accounting for correlation between cases in the same cluster.
Results:: Sequences were analyzed for 30,323 persons; 13 rapidly growing clusters were identified. These clusters had a transmission rate of 34/100 person-years. Compared with the 30,127 persons not in these clusters, the 196 persons in these 13 clusters were disproportionately men who have sex with men (MSM) (94% vs. 62%, P< 0.0001), aged < 30 years (68% vs. 41%, P< 0.0001), Hispanic/Latino (49% vs. 28%, P< 0.0001), and, specifically, young Hispanic/Latino MSM (32% vs. 9%, P< 0.0001). The clusters included high levels of transmitted drug resistance (43% vs. 20%, p=0.0006).
Conclusions:: This approach identified a small number of clusters with a transmission rate more than 8 times that of previous national estimates. These findings highlight the extent of rapid transmission among young Hispanic/Latino MSM, suggesting the need for prevention efforts that focus on this population. Identifying clusters of active transmission can help programs effectively direct limited public health resources.