An HIV Outbreak Among Homeless People Who Inject Drugs in Seattle, 2018

HIV diagnoses among people who inject drugs have been falling in the United States — but a large outbreak in rural Indiana in 2014–2015 showed how vulnerable they remain. In 2018, Seattle proved that a big city with strong HIV programs is vulnerable too.

What was found

In August 2018, Public Health–Seattle & King County (PHSKC) identified a cluster of HIV cases among people living homeless, most of whom injected drugs.

Across King County, 27 HIV cases were diagnosed among women and MSW who inject drugs from January 1 into November 2018 — a 286% increase over the seven diagnosed in all of 2017.

How it came to light

1. In July 2018, a man living homeless in north Seattle went to an emergency department with fever and tested positive for acute HIV. He didn't inject drugs but had paid a woman for sex.
2. She was living homeless nearby, injected heroin, and had tested HIV-positive in June.
3. A disease intervention specialist's social media search linked her to a man who injected drugs, lived homeless, and had tested positive in July.
4. PHSKC also knew of three other recently diagnosed women who injected drugs and lived homeless in north Seattle, with no known links to the others.
5. Molecular analysis with HIV-TRACE — a program that uses the virus's genetic sequences to find related infections — showed that four recent cases, including those three women, had related strains, and tied the recent cases to earlier diagnoses from 2008–2017 and to two more found in September 2018.

By November 20, 2018, the cluster held 23 cases. Transmission had been going on, at least on and off, since 2008, and sped up in 2017–2018.

The transmission network, 2008–2018 (23 people, including sex partners and people with molecularly linked strains). A molecular link doesn't necessarily mean direct contact, and line lengths don't show how closely strains are related. CDC

The response

• August 3: a disease intervention specialist links the first three cases; four days later, PHSKC alerts medical and social service providers.
• Emergency departments: PHSKC contacted several, including the hospital nearest the patients. They asked providers to screen more people who inject drugs or live homeless, and at least three are building opt-out HIV screening programs. ED screening has found one cluster case.
• King County Jail, from August 20: opt-out HIV testing at health assessments 10–14 days after booking, and at booking when resources allow — one new case found, not linked to the cluster.
• Street outreach in north Seattle: testing, condoms and syringe services. By November 15 it had tested 534 people and found four related cases.
• Wider access to HIV testing and PrEP through the STD clinic, syringe programs and a mobile clinic for north Seattle women who trade sex or live homeless.
• A rapid assessment of what people who inject drugs or live homeless need, aiming to expand services including medication-assisted treatment.

Why it happened here

King County wasn't on CDC's list of the 5% of U.S. counties at highest risk of HIV or hepatitis C outbreaks among people who inject drugs. By most measures it was doing well:

Yet — like a recent outbreak in Massachusetts — Seattle's shows that this vulnerability is widespread. The authors point to:

• Gaps in services: the outbreak was concentrated where syringe and clinical services were limited.
• Overdose and homelessness: heroin overdose deaths in the county rose 264% from 2007 to 2018, and the number of residents living homeless rose 47% from 2007 to 2017. In a 2017 survey of syringe program users, 43% were living homeless and another 26% were unstably housed. A fast-growing group of people who inject drugs and live homeless — who find services especially hard to reach — created a new susceptibility to HIV.

Lessons

• Molecular surveillance works, if it's fast. Looking back, 10 related cases were diagnosed between December 2016 and August 2018, before the cluster was spotted. Faster analysis could have triggered an earlier response and perhaps prevented some infections. CDC has begun a national effort to expand molecular HIV analysis, and the federal Ending the HIV Epidemic plan makes it one of four central pillars.
• Reaching the most marginalized is hard. In mid-November 2018, seven of the 21 living people in the cluster weren't in HIV care; disease intervention specialists were searching for them to link them to a walk-in HIV clinic.
• Other health departments should check whether similar outbreaks are happening in their areas.

Sources

Based on Golden MR, Lechtenberg R, Glick SN, et al., "Outbreak of Human Immunodeficiency Virus Infection Among Heterosexual Persons Who Are Living Homeless and Inject Drugs — Seattle, Washington, 2018," MMWR volume 68, number 15, Centers for Disease Control and Prevention; a work of the United States government in the public domain. The report ends the 2018 count of 27 cases on November 15 in one place and November 30 in another, and puts the cluster's earlier (2008–2017) cases at eight in one place and nine in another; neither end date nor that count is given here.