Repeat Sexually Transmitted Diseases and Core Transmitters Kyle Bernstein, ScM. Johns Hopkins Bloomberg School of Public Health Baltimore City Health Department

Core Transmitters The reproductive rate equation –R=βcd When R>1  Epidemic transmission When R=1  Endemic Disease –Within the “core” R>1, outside R<1 Disease remains endemic outside the core through interactions within the core Thomas and Tucker, JID 1996

=x Conceptual model Risk of acquisition x Probability that partner is infected Transmission efficiency Rate of exposure to potentially infected partner PathogenPathogen virulence IndividualNumber of partners Acts per partner Host susceptibility Type of sex act Condom use PartnerPartner susceptibility Partner health seeking behavior Partner susceptibility Partner health seeking behavior NetworkCommunity structurePrevalence in community

Definitions of STD Core Group whose prevalence of GC >20% Sex workers Persons who have very many sexual contacts Very sexually active women and men who are asymptomatic when infectious Census tracts that are source of ≥50% of reported cases Those with high rates of partner acquisition GC transmitter Drug using sex workers recurrently infected with STDs Adolescent males in detention People with ≥ 5 sex partners per year People with cluster of high-risk behaviors Thomas and Tucker, JID 1996

Repeat STDs While effective treatment is available, GC re-infection is common and contributes disproportionately to overall GC morbidity Noble et al, STD, 1977 Brooks, et al, JID, 1978 Kinghorn, et al, STD, 1982 McEvoy and Le Furgy, STD, 1988 Ellen et al, JID, 1997 Fox et al, AJE 1999 Fortenberry, STD 1999

Repeaters as Core Advantages –Objective –Biologic Outcome –Fits well with transmission model –Correlates with high- risk behavior Disadvantages –Biologic outcome –Requires extensive data –May not represent those who sustain endemic disease

Repeaters and Baltimore-GC Mehta et al, STI 2003 –Retrospective clinical record review ( ) in two STD clinics 15.5% of individuals re-infected with GC (23.8% of total visits). Men - ≤ 25, ≥ 2 sex part in last month, and sex with CSW independent risk factors Female - ≥ 2 sex part in last month, “any” condom use, CSW independent risk factors Interactions- Generally coming to clinic as a contact was protective, except among high-risk clients (CSW)

Spatial Analysis of Repeaters Bernstein et al, AJE (In Press) –Retrospective morbidity record review ( ) for all GC reported in Baltimore City 9% of individuals re-infected with GC Repeaters more likely to be male, younger

Summary of Repeaters in Baltimore In Baltimore, repeaters compose a large proportion of the GC morbidity Traits of repeaters appear consistent with notions of core transmitters

How can interventions be targeted at repeaters? Geographic targeting –Resource and cost draining Partner delivered therapy –Regulatory barriers Active follow-up for all reported repeaters –Private sector cooperation required

The Baltimore Repeaters Project From Sept 2003 – Sept 2004 all GC cases reported from the two Baltimore City STD clinics with confirmed treatment will be re-assessed three months for re-infection –Urine sample PCR tested for GC/CT –Behavioral Interview Individual level Partner level Location of sexual partner recruitment –Por PCR typing to determine GC strain diversity and if individuals are re-infected with same strains

Program Implications At the clinic level, can demographic, clinical, or behavioral level information be found as predictors of repeat infection? Can these correlates be used to provide active follow-up and management of clients most likely to repeat? Can identification and treatment of repeaters who would not be diagnosed otherwise impact the area’s global burden of GC infections? Reduction of duration of infectivity  reduce R

Preliminary Results From Sept Feb 13, 2004 –250 individuals eligible –57 (22.8%) contacted and provided specimens 3 (5.3%) CT+ 2 (3.5%) GC + –43 (17.2%) refusals –63 (25.2%) UTL –15 (6%) Jail/Out of Jurisdiction –71 (28.4%) Open Cases –5 Additional clients GC + in follow-up window

Acknowledgments Glen Olthoff, Emily Erbelding, Jon Ellen, Jonathan Zenilman, Caroline Fichtenberg NIH Training Grant #T32 A Woodrow Wilson/Johnson & Johnson Women’s Health Dissertation Grant