Rapid HIV Transmission Clusters

By: Ranier Simons, ADAP Blog Guest Contributor

Despite the many medical and scientific advances in the fight against HIV/AIDS, the numbers of new infections and AIDS-related deaths remain markedly high. Globally, in 2021, there were 1.5 million new infections and 650,000 AIDS deaths.[1] Avoidable HIV infections occur among developing and first-world countries, including the United States. The U.S. Centers for Disease Control & Prevention (CDC) reported one such troubling trend in the September 23, 2022, Morbidity and Mortality Weekly Report (MMWR): clusters of rapid HIV transmission among gay, bisexual and other MSM (men who have sex with men).

MSM accounted for 68 percent of new HIV diagnoses in the United States, in 2020. The recent MMWR report examined clusters of rapid HIV transmission identified by the National HIV Surveillance System (NHSS). The NHSS is the primary source for monitoring HIV in the United States. The surveillance system gathers, analyzes, and reports a plethora of information regarding new and existing HIV infections. The CDC provides funding and partners with local and state health departments to collect the data.[2] Part of this data includes HIV-1 nucleotide sequences taken from the bloodwork of infected individuals. Utilizing this database, researchers identified large molecular clusters of rapid transmission. In other words, they could identify clusters of people who shared the same ‘flavor’ of the HIV virus.

Photo Source: CDC, MMWR

But as the ADAP Advocacy Association noted several years ago, NHSS also is associated with numerous patient concerns, namely privacy infringement and fueling stigma. Whereas some public health advocates may argue such surveillance is necessary in the fight against HIV/AIDS, others remain skeptical whether the benefits outweigh the risks. For the purpose of this particular blog, that debate will be set aside.

Identifying clusters enables public health professionals to identify demographic and geographic areas of HIV transmission. One hundred and thirty-six rapid transmission clusters were identified during 2018-2019 and followed through to December 2021. Rapid transmission was defined as a cluster with five or more diagnoses in the most recent 12 months.[3] A large cluster was defined as one that grew to contain more than 25 people as of December 2021. Thirty-eight large clusters were detected in 2018-2019. MSM comprised the majority of 29 of those 38 clusters. Also, most clusters of rapid HIV transmission were among MSM. The median growth rate was nine people added to a cluster per year.[3] The MSM majority clusters existed in many different regions of the country, most involving multiple states.

There were 2,901 people in the 136 molecular clusters with rapid transmission. The 38 large clusters contained 1,533 (53%) of the 2,901. The 29 clusters of those 38, which were primarily MSM, contained 985 people. Six clusters were primarily people who injected drugs, and three had no defined transmission category.

Photo Source: POZ

Concerning racial or ethnic groups, as of December 2021, African-Americans were the largest group in 13 of the large MSM clusters, Caucasians were the largest group in nine of the clusters, and Hispanic people were the largest in seven of them.[3] Geographically, the most common region in 14 of the 29 MSM clusters was the South, and 23 clusters included people from multiple regions.[3] As a whole, 70 % lived in large centralized metropolitan areas or large fringe metropolitan areas, and 20% lived in medium metropolitan regions.[3]

Clusters indicate areas where intervention efforts are not successful. Continuing cluster analysis will demonstrate how treatment, prevention, and testing efforts must be modified to be more effective in the affected communities. The rate of transmission in the large MSM clusters was six times the overall U.S. population average for transmission.[3] Approximately 80% of new HIV transmissions are from people unaware of their status or not receiving regular care.[4] The September report is a wake-up call to the desperate need for an effective concerted, multi-pronged social, political, and financial revolution if we are to reach the goal of eradicating HIV.

[1] UNAIDS. (2022) Millions of lives at risk as progress against AIDS falters. Retrieved from https://www.unaids.org/en/resources/presscentre/pressreleaseandstatementarchive/2022/july/20220727_global-aids-update
[2] Centers for Disease Control and Prevention. (2021, August 9). HIV Statistics Center. Retrived from https://www.cdc.gov/hiv/statistics/index.html
[3] Perez, S. PhD et. al (2022). Clusters of Rapid HIV Transmission Among Gay, Bisexual, and Other Men Who Have Sex with Men — United States, 2018–2021. Morbidity and Mortality Weekly Report, 71(38), 1201-1206, https://doi.org/10.15585/mmwr.mm7138a1
[4] Li, Zihao PhD et. al. (2019). Vital Signs: HIV Transmission Along the Continuum of Care — United States, 2016. Morbidity and Mortality Weekly Report, 68(11), 267-272, https://doi.org/10.15585/mmwr.mm6811e1

Disclaimer: Guest blogs do not necessarily reflect the views of the ADAP Advocacy Association, but rather they provide a neutral platform whereby the author serves to promote open, honest discussion about public health-related issues and updates.