The Centers for Disease Control and Prevention (CDC) has published a report about the recent outbreak of HIV among heterosexual homeless people who inject drugs (PWID) in King County, Washington, which includes Seattle.

The opioid epidemic has apparently caused a rise in the national HIV infection rate among PWID in recent years, following nearly two decades of hard-fought declines. Meanwhile, Seattle’s homeless population has swelled as the city faces an affordable housing crisis.

Of the approximately 21,000 heterosexual women and men who inject drugs in King County, only 1% to 3% currently have HIV; of those, 80% are on antiretroviral treatment and have a fully suppressed viral load. About 79% of the heterosexual PWID population uses syringe services programs. The sharing of injection equipment has declined over time among local PWID. 

Publishing their findings in the Morbidity and Mortality Weekly Report, researchers described the findings from an investigation conducted by Public Health — Seattle & King County and the University of Washington.

Between February and mid-November 2018, investigators identified 14 related cases of HIV among heterosexual men and women who inject drugs and their sex partners. All of these individuals were homeless and living within about a 3-square-mile area. Using molecular surveillance—a cutting-edge type of HIV surveillance that relies on genetic analyses of the virus to determine whether certain individuals have related strains—the investigators found that these 14 individuals had HIV that was part of a related cluster of infections that had been diagnosed since 2008.

All told, between January and mid-November 2018, King County saw 27 diagnoses of HIV among heterosexual men and women who inject drugs. This represented a 3.9-fold increase compared with the seven diagnoses among members of this demographic in 2017.

The HIV diagnosis rate in the overall King County population declined by 51% between 2008 and 2017.

“This outbreak,” the study authors concluded, “highlights the vulnerability of persons who inject drugs, particularly those who also are living homeless, to outbreaks of HIV infection, even in areas with high levels of viral suppression and large syringe services programs.”

To read the report, click here.