In January 2019, the West Virginia Bureau for Public Health (BPH) detected an increase in HIV diagnoses among people who inject drugs (PWID) in Cabell County, which has experienced high rates of substance use disorder in recent years. Responding to HIV clusters and outbreaks is one of four pillars of the federal Ending the HIV Epidemic initiative and can be used to guide activities supporting the other pillars (diagnose, treat, prevent). BPH, Cabell-Huntington Health Department, and CDC collaborated to conduct a robust investigation and response.
We analyzed surveillance data, including HIV-1 polymerase data, reported to BPH through November 2019; links were identified at ≤0.005 nucleotide substitutions/site. Outbreak cases were defined as HIV diagnoses during January 1, 2018–October 9, 2019 among 1) PWID linked to Cabell County, 2) their sex or injecting partners, or 3) people with linked sequences. We estimated transmission rate and timing of infections via molecular clock phylogenetic analysis and identified suspected recent infections based on initial viral load and CD4+ cell count, report of last negative HIV test, or presence in a molecular cluster. State, federal, and local partners implemented a comprehensive response.
We identified 81 cases, a 2,285% increase above the 2015–2017 annual average of 2 cases. Most people were male (58%), aged 20-39 years (74%), and white (91%). Almost all (99%) were PWID; many (73%) reported unstable housing. In all, 69 (85%) had ≥1 measure of recent HIV infection. Among 45 people with an available HIV-1 sequence, 41 (91%) were in a large molecular cluster with 35/41 (85%) inferred transmissions occurring after January 1, 2018. Estimated transmission rate in the molecular cluster was 78 per 100 person-years. A comprehensive response featured activities from all four pillars (figure).
Evidence of rapid transmission in this outbreak—the largest relative increase over baseline in the United States since the large 2015 outbreak in rural Scott County, Indiana—galvanized robust collaboration among federal, state, and local partners. Response interventions supported diagnosis, treatment, and prevention (including expansion of preexposure prophylaxis and syringe services); many activities are now being expanded in other counties statewide. Cluster and outbreak response requires increased coordination and creativity to improve service delivery to vulnerable communities.