Brief Report: National HIV Molecular Cluster Detection Supports Local Cluster Detection

Area of Science:

• Epidemiology
• Molecular epidemiology
• Public Health Surveillance

Background:

• The Centers for Disease Control and Prevention (CDC) and health departments analyze HIV sequences to detect molecular clusters indicating rapid transmission.
• Local analyses offer timeliness but are limited by available sequences, potentially missing clusters spanning multiple jurisdictions.
• This study evaluates the added value of national analyses for detecting clusters missed or partially identified by local efforts.

Purpose of the Study:

• To assess the benefits of national HIV sequence analysis in identifying transmission clusters.
• To determine how often local analyses miss or delay the detection of priority HIV clusters.
• To quantify the proportion of cluster members identifiable through local surveillance.

Main Methods:

• Reviewed national quarterly HIV sequence analyses from September 2021 to June 2023.
• Defined priority clusters as ≥5 diagnoses within 12 months and genetic distance ≤0.005 substitutions/site.
• Simulated local detection capabilities and calculated the proportion of cluster members identified locally.

Main Results:

• National analysis identified 149 priority clusters; 21% were missed by local analyses.
• Local analyses concurrently detected 61% of clusters, with 18% showing delayed detection (median 59 days).
• In concurrently detected clusters, an average of 91% of members were identified locally.

Conclusions:

• National HIV sequence analysis detects clusters missed by local efforts and identifies additional cases earlier.
• National cluster detection complements and enhances local surveillance activities.
• Integrating national and local analyses improves the comprehensive understanding of HIV transmission dynamics.