A public health approach to monitoring HIV with resistance to HIV pre-exposure prophylaxis.

BACKGROUND: The risk of HIV pre-exposure prophylaxis (PrEP) failure with sufficient medication adherence is extremely low but has occurred due to transmission of a viral strain with mutations conferring resistance to PrEP components tenofovir (TDF) and emtricitabine (FTC). The extent to which such strains are circulating in the population is unknown. METHODS: We used HIV surveillance data to describe primary and overall TDF/FTC resistance and concurrent viremia among people living with HIV (PLWH). HIV genotypes conducted for clinical purposes are reported as part of HIV surveillance. We examined the prevalence of HIV strains with mutations conferring intermediate to high level resistance to TDF/FTC, defining primary resistance (predominantly K65R and M184I/V mutations) among sequences reported within 3 months of HIV diagnosis and total resistance for sequences reported at any time. We examined trends in primary resistance during 2010-2019 and total resistance among all PLWH in 2019. We also monitored resistance with viremia (≥1,000 copies/mL) at the end of 2019 among PLWH. RESULTS: Between 2010 and 2019, 2,172 King County residents were diagnosed with HIV; 1,557 (72%) had a genotypic resistance test within three months; three (0.2%) had primary TDF/FTC resistance with both K65R and M184I/V mutations. Adding isolated resistance for each drug resulted in 0.3% with primary TDF resistance and 0.8% with primary FTC resistance. Of 7,056 PLWH in 2019, 4,032 (57%) had genotype results, 241 (6%) had TDF/FTC resistance and 15 (0.4% of those with a genotype result) had viremia and TDF/FTC resistance. CONCLUSIONS: Primary resistance and viremia combined with TDF/FTC resistance are uncommon in King County. Monitoring trends in TDF/FTC resistance coupled with interventions to help ensure PLWH achieve and maintain viral suppression may help ensure that PrEP failure remains rare.

Detection and Response to an HIV Cluster: People Living Homeless and Using Drugs in Seattle, Washington.

INTRODUCTION: The HIV epidemic in King County, Washington has traditionally been highly concentrated among men who have sex with men, and incidence has gradually declined over 2 decades. In 2018, King County experienced a geographically concentrated outbreak of HIV among heterosexual people who inject drugs. METHODS: Data sources to describe the 2018 outbreak and King County's response were partner services interview data, HIV case reports, syringe service program client surveys, hospital data, and data from a rapid needs assessment of homeless individuals and people who inject drugs. In 2020, the authors examined the impact of delays in molecular sequence analyses and cluster member size thresholds, for identifying genetically similar clusters, on the timing of outbreak identification. RESULTS: In 2018, the health department identified a North Seattle cluster, growing to 30 people with related HIV infections diagnosed in 2008-2019. In total, 70% of cluster members were female, 77% were people who inject drugs, 87% were homeless, and 27% reported exchanging sex. Intervention activities included a rapid needs assessment, 2,485 HIV screening tests in a jail and other outreach settings, provision of 87,488 clean syringes in the outbreak area, and public communications. A lower cluster size threshold and more rapid receipt and analyses of data would have identified this outbreak 4-16 months earlier. CONCLUSIONS: This outbreak shows the vulnerability of people who inject drugs to HIV infection, even in areas with robust syringe service programs and declining HIV epidemics. Although molecular HIV surveillance did not identify this outbreak, it may have done so with a lower threshold for defining clusters and more rapid receipt and analyses of HIV genetic sequences.