HIV Clusters Reported by State and Local Health Departments in the United States, 2020-2022

Area of Science:

• Epidemiology
• Public Health
• Infectious Disease Surveillance

Background:

• Rapid HIV transmission clusters signal gaps in current prevention, testing, and care services.
• The Centers for Disease Control and Prevention (CDC) initiated funding for U.S. health departments (HDs) in 2018 to address HIV clusters.
• HDs commenced reporting identified clusters to the CDC starting in January 2020.

Purpose of the Study:

• To characterize HIV clusters detected by U.S. health departments.
• To describe the investigation and response activities undertaken for these clusters.
• To evaluate the effectiveness of cluster detection and response in addressing HIV transmission networks.

Main Methods:

• Analysis of HIV cluster data reported to the CDC from 2020-2022.
• Description of cluster characteristics including detection method, size, and transmission category.
• Review of health department investigation and response activities, such as partner services and focused testing.

Main Results:

• During 2020-2022, 45 HDs reported 322 HIV clusters, predominantly detected via molecular analysis (75%) and concentrated in the South (46%).
• Most clusters (75%) involved predominant sexual transmission, with a median size of 10 persons for molecular clusters.
• Response activities were implemented in 95% of investigated clusters, including partner services (64%) and focused testing (13%), with 11% of tested partners receiving new HIV diagnoses.

Conclusions:

• Health department-led HIV cluster detection successfully identified numerous transmission networks.
• Tailored response strategies effectively intervened in networks characterized by rapid transmission and high rates of undiagnosed infections.
• Cluster detection and response is a vital strategy for identifying and mitigating gaps in HIV prevention, testing, and care.