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HIV Epidemiology


HIV Epidemiology

Contact Information
Los Angeles County
Department of Public Health
HIV Epidemiology, DHSP                       600 S. Commonwealth Ave. Suite 1920
Los Angeles, CA 90005
Phone: (213) 351-8196
Fax: (213) 487-9386


        LAC's ZIP code level data/maps on HIV

HIV Epidemiology - Unlinked HIV Seroprevalence Surveys in Methadone Treatment Centers

Since 1981, when acquired immunodeficiency syndrome (AIDS) was recognized in the United States, approximately one third of AIDS cases reported to the CDC have been associated with injection drug use, either directly through sharing of drug-injection equipment or indirectly through sexual or perinatal transmission. CDC has conducted unlinked HIV seroprevalence surveys in a variety of clinical settings since 1987.

In 1988, the Unlinked HIV Seroprevalence Surveys in Drug Treatment Centers were implemented in order to obtain unbiased HIV prevalence estimates among clients at methadone treatment centers in Los Angeles County. For the past 10 years, the data collected for the unlinked seroprevalence study have proven invaluable in terms of monitoring trends of HIV prevalence among injection and illicit drugs users in Los Angeles County. HIV seroprevalence surveys conducted in this high-risk population provide critical information for planning the allocation of scarce HIV/AIDS resources and the development of funding priorities in Los Angeles County.


  1. To obtain unbiased estimates of HIV seroprevalence for clients in methadone treatment centers overall, and for subgroups defined by gender, age group, race/ethnicity, geographic location, risk exposure/behavior variables, and treatment modality.
  2. To monitor trends in HIV infection by demographic and risk exposure/behavior subgroups.
  3. To identify subgroups at highest risk for HIV infection and, therefore, in need of more comprehensive HIV/AIDS prevention programs.
  4. To supply data than can be used to target and evaluate HIV prevention programs.

Study Design:

The HIV Epidemiology Program in collaboration with West County Medical Clinic, Narcotics Prevention Project, and Western Pacific Panorama Medical Clinic conducts the unlinked seroprevalence study. Methadone treatment clients eligible for the unlinked serosurvey include those persons who: 1) are under evaluation for admission to drug treatment in which a routine blood test has been ordered and 2) have used illicit drugs or prescription drugs for non-prescribed use at least once in within the past 12 months. After laboratory results have been obtained for syphilis blood specimens, leftover serum is secured for unlinked HIV testing. The Los Angeles County Public Health Laboratory conducts HIV-antibody testing after all patient identifiers are removed from each tube of remnant serum. Results of the unlinked HIV tests are forwarded to the HIV Epidemiology Program and are matched to each client's demographic characteristics, risk behavior, and drug use obtained from client files maintained at each methadone site. HIV test results are linked to this information through use of an unique ID number common to all forms. Unbiased estimates of HIV prevalence in the methadone treatment centers are based on the sample of clients who accept and refuse confidential HIVtesting.

Contact Persons:

Mark Weber, Ph.D.

Bill Reidy, M.H.A.
Research Analyst

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