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Epidemiologic Notes and Reports Alternative Case-Finding Methods in a Crack-Related Syphilis Epidemic -- Philadelphia
Use of crack cocaine and exchange of drugs for sex have been identified as substantial contributors to the syphilis epidemic in Philadelphia and other locations in the United States (1-4). In Philadelphia, from 1985 through 1989, the number of reported cases of early syphilis (primary, secondary, and early latent stages) increased 551%, from 696 to 4528 cases per year. Among 2473 persons with early syphilis interviewed by the Philadelphia Department of Public Health (PDPH) from January through July 1990, 48% reported they or a sex partner* used crack cocaine, and 31% reported exchanging drugs or money for sex (not all of those interviewed answered both questions).
Traditional approaches to the control of syphilis that emphasize partner notification have not been effective in halting this epidemic. The partner notification approach requires public health workers to identify sex partners of a person with a sexually transmissible disease (e.g., syphilis) and then to contact these sex partners to provide examination and curative or preventive treatment. However, because persons who are involved in the exchange of drugs and/or money for sex often cannot or will not provide sufficient information about sex partners to enable public health authorities to locate those partners (2,4,5), alternative case-finding methods are needed. This report describes efforts by the PDPH to identify persons infected with Treponema pallidum by using serologic screening at locations where crack cocaine is used.
The alternative intervention used by PDPH included two components:
On June 25, 1990, an interview of the index patient, a bisexual female crack user with secondary syphilis, identified three sex partners, three high-risk associates***, and the location of a crack house (i.e., a setting where crack cocaine is sold and/or used). Subsequent reinterviews of the index patient and visits during which she accompanied PDPH staff to different neighborhoods identified two additional sex partners, 11 additional high-risk associates, and a second crack house. Examinations and interviews of these sex partners and high-risk associates identified a chain of infection involving 14 cases of early syphilis (two primary, four secondary, and eight early latent).
In addition, a syphilis patient who was not initially known to be linked to the first chain of infection identified a third crack house. Serologic screening of 21 persons at that crack house detected eight new cases of early latent syphilis. Four of these persons were linked (as sex partners or high-risk associates) with the patient who had identified the crack house and/or with three other persons with previously detected cases of early syphilis. For the other four persons, the only identified link with this second chain of infection was crack use at a common location.
The two chains of infection were linked through a high-risk associate of the original index patient; the associate was lost to follow-up before PDPH determined her infection status. Investigation of these two chains of infection resulted in preventive treatment (for possible incubating syphilis) of 19 sexually exposed persons. Screening Activity Team
In July 1990, the PDPH Sexually Transmitted Disease (STD) Control Program began to serologically screen persons at high-risk locations where crack is used or sold (including crack houses, drug-sale areas, brothels, prostitution strips, and shooting galleries (i.e., a setting where illegal drugs are injected)). Information about potential screening sites was provided by STD staff who elicited information about such sites during their field work and interviews with persons infected with syphilis.
From July 9 through October 9, 1990, the SAT worked an average of 3 hours each afternoon in the field. Blood was drawn from persons who voluntarily consented, and the serum samples were tested the following morning using the rapid plasma reagin (RPR) test. The SAT then returned to the field to offer examination and treatment (at the STD clinic) to persons with reactive serologic results and no history of treatment.
Of 372 persons screened, 100 (27%) tested reactive on the RPR card test (Figure 1). Of these, 44 were successfully treated for syphilis, 21 had been previously treated, and 33 were lost to follow-up; two had false-positive serologic results based on negative confirmatory testing using the microhemagglutination for T. pallidum test. Of the 44 newly treated persons, four (9%) had primary, six (14%) secondary, 32 (73%) early latent, and two (5%) late latent syphilis; one woman with secondary and one woman with early latent syphilis were brought to treatment in their eighth month of pregnancy. Reported by: AK Mellinger, MD, M Goldberg, A Wade, MA, PY Brown, GA Hughes, JP Lutz, W Harrington-Lyon, Philadelphia Dept of Public Health. Div of STD/HIV Prevention, Center for Prevention Svcs, CDC.
Editorial Note: Partner notification is an important part of efforts to control the spread of syphilis. However, in the current epidemic, many infected persons are users of illegal drugs who often cannot or will not provide sufficient information to allow STD staff to locate and offer examination and treatment to sex partners (2,4,5). The alternative case-finding method used by PDPH was based on serologic screening at locations identified during interviews of patients with early syphilis and was successful in identifying infected patients.
Partner notification permits preventive treatment of exposed persons before the onset of disease and, therefore, infectivity. In contrast, persons infected with syphilis who are identified through serologic screening usually have latent disease; many of these are already past the period of maximum infectivity. Nonetheless, the SAT identified a substantial number of persons with primary and secondary syphilis (3% of those tested), possibly because information obtained from patients with early-stage syphilis was used to target the locations for serologic screening. Detection and treatment of patients in these highly infectious stages are likely to be more effective in reducing disease transmission than detection and treatment of patients with latent syphilis.
The SAT was accepted at most high-risk locations except for some crack houses. When access was initially denied, occupants were invited outside, often with success. When efforts to contact crack house occupants failed, the SAT attempted to schedule a visit at a time more agreeable to the owner. This approach usually resulted in cooperation and access to occupants.
The SAT approach appeared to be more effective than other efforts to identify high-prevalence populations for targeted screening. For example, among men tested in gay bathhouses in 1975-76 in Los Angeles and Denver, overall prevalences of RPR reactivity were 20% and 4%, and of untreated syphilis were 3% and 1% (all with latent syphilis), respectively (8).
PDPH staff successfully obtained the cooperation of persons who, because of the illegal nature of their activities, might be expected to resist these efforts. Outreach efforts such as this could also increase awareness of the epidemic in the affected community. Increased awareness of the epidemic could enhance control efforts by prompting early self-identification of infected persons and result in high-risk persons adopting safer sexual practices.
Despite the brief (24 hours) time required to obtain test results, a substantial proportion (33%) of seroreactive persons could not be located for examination/treatment. Thus, targeted screening might be more effective if immediate RPR testing is performed at the time of phlebotomy, allowing treatment and partner notification interviews at that time for those persons who are seroreactive and considered likely to have untreated syphilis.
The high rate of infection among persons who had been targeted because of their proximity to sites of crack cocaine use reinforces evidence from other studies that suggest that crack and sites of crack use and sale play an important role in the syphilis epidemic. Efforts such as those of PDPH to use information about the dynamics of the epidemic as a basis for implementing interventions should be evaluated in other geographic areas. Evaluations of alternative case-finding methods should ideally assess their effectiveness in reducing syphilis transmission and their cost-effectiveness in identifying case-patients for curative or preventive treatment.
*A person who had sexual contact with the index patient at a time when transmission between the two (in either direction) could have occurred.
**Cluster investigation techniques are designed to identify persons (other than sex partners) at high risk for syphilis.
***Persons (other than sex partners) identified by cluster investigation techniques as having high risk for syphilis.
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