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Press Release

Finding Hidden and Lost HIV Patients in Los Angeles County: Mining Social Networks to Approach and Engage Them in Care
California HIV/AIDS Research Program
               University of California, Office of the President
               300 Lakeside Drive, 6th Floor
               Oakland, California 94612‑3550
               Tel (510) 987‑9855; Fax (510) 587-6325
Contact:  Dr. Lisa Loeb Stanga, California HIV/AIDS Research Program
Cell 415-806-2489, email


Finding Hidden and Lost HIV Patients
in Los Angeles County:  Mining Social Networks
to Approach and Engage Them in Care

(Los Angeles)  Sprinkled among every community are people who seem to know everyone. Influential and connected, they're the nexus of large and invisible social circles. 

Those are the people, realized Dr. Amy Rock Wohl, who may be able to help slow the spread of HIV in hard-to-reach populations – by linking their friends to care.

These hard to reach folks, the hidden and lost HIV patients, "have been the needle in the haystack for many years," said Wohl, particularly in Los Angeles County, where approximately 51% of persons living with HIV in 2013 were successfully receiving ongoing treatment. "We've had trouble bringing them into the clinic for the care they need.”

“A large proportion have a history of homelessness," said Wohl, formerly chief epidemiologist in the county’s Division of HIV and STD Programs "They're 'off the grid,' and wouldn't normally come to the attention of these more traditional care providers."  

The challenge was to work with well-connected individuals, enlist their help, and then motivate others in their social circle to join in.  "We used a social network approach," calling it Project Engage, said Wohl.

It is the first time this strategy, funded by the California HIV/AIDS Research Program and the U.S. Centers for Disease Control and Prevention, has been used to successfully identify hidden HIV-positive individuals who aren't getting treatment – the so-called “lost patients” – and get them the care they need.   

"We identified people who knew other people who were HIV-positive and not seeing a doctor -- and were willing to talk to their friends and acquaintances about the importance of being in care, and refer them to us," she said. 

The approach worked: 91% of the out-of-care patients got HIV care within a year, and 72% were still getting that care 6 months to one year later.  

“This tremendous success rate of getting people back into care is very important not only for their health but also because it has been estimated that nearly two-thirds of new HIV infections are transmitted by people who have been diagnosed with HIV but are not receiving consistent medical care”, said Dr. George Lemp, Director of the California HIV/AIDS Research Program at the University of California’s Office of the President.

Just like other informal social groups, hard-to-reach communities also have invisible internal networks.  Wohl wanted to harness this strength and use it to help reach the truly needy – such as homeless people living with untreated HIV, or people being released from jail and needing HIV care and medicine.  Such patients may need extra help to get their virus under control – and getting their viral loads down will help protect them from transmitting HIV to others.

To find them, Wohl's team worked closely with staff at HIV clinics and community-based organizations who are familiar with this population, and are comfortable working outdoors in public areas.  They enlisted a technique that sociologists and statisticians call “snowball sampling,” where research participants recruit other participants for a test or study.

They identified people with large social networks -- dubbed "seeds" -- who likely knew HIV-infected people who weren't getting care. They could serve as ambassadors for care, the team thought, recommending it to their friends and acquaintances.

These "seeds" were paid $40 when they completed a questionnaire, and another $40 if a person they referred, called an "alter," came in for a medical visit.  The "alter" also got paid. They were given $40 to take the questionnaire, and another $40 if they referred someone else who came in for care.

One man had an extraordinary knack of making friends and acquaintances. Of his large network, said Wohl, more than 59 people eventually enrolled in Project Engage for care. So he pocketed $2,360. 

But such people, while powerfully connected, are the exception, she said. "Most people only knew one or two people who were HIV positive and out of care, and who were willing to talk to and recruit those people," she said. The project was successful because the seeds led them to those one or two other hard-to-reach patients, who otherwise might not have gotten any personalized attention.  

Of the 112 people who came to Project Engage for care, about two-thirds (67 percent) were referred by "seeds," and one-third (33 percent) arrived through direct recruitment (such as posters in the community and direct contacts with staffers).

These patients had struggled with tough times. About 78 percent had been homeless in the six months before project enrollment, almost 50% had injected drugs during their lives, and 58 percent had been incarcerated within the past year.  Nearly all (89 percent) were poor, with annual incomes below $12,000. On average, they had been diagnosed with HIV for about 12 years.  While the participants had not received any HIV care for an average of 12 months , only 27% were virally suppressed at the time that project staff linked them to care.

After enrolling in Project Engage, just over two-thirds (69 percent) were linked to care within 3 months. The new enrollees were more socially disadvantaged than the "seeds" that recruited them, affirming the notion that these "seeds” have unique access to a population that isn't easily reached using standard approaches, said Wohl.

This type of recruitment takes a lot of time, she conceded. It also demands other resources, such as two full time outreach staff and one part-time project coordinator. And follow-up is important to keep people in care, through robust HIV clinic support services.

But the strategy worked. It succeeded in suppressing the levels of virus in these patients, the team found.  That reduces the risk that they’ll transmit it to others -- helping protect a vulnerable population. "We found hidden populations of HIV positive persons," said Wohl, “who may not have been accessed through more traditional recruiting venues."

The Los Angeles team has taken the lessons learned from this project and scaled it up into a "linkage-to-care" program across Los Angeles County.  “We have continued the great work from this research program in our newly launched HIV Linkage and Re-engagement Program (LRP),” said Sophia Rumanes, Chief of Direct Services at Los Angeles County Department of Public Health, Division of HIV and STD Programs.  “We now have eight Health Navigators that are helping individuals who have fallen out of consistent HIV medical care by linking them back into care, using the techniques that the Project Engage research showed can work.”

Results from the study were published this month in the Journal of Acquired Immune Deficiency Syndromes (75[2]:190-197, June 1, 2017) as “Project Engage: Snowball Sampling and Direct Recruitment to Identify and Link Hard-to-Reach HIV-Infected Persons Who Are Out of Care,” which can be accessed at