Assessment of a geographically targeted field intervention on gonorrhea incidence in two New York state counties

Background and Objectives: Using study findings that demonstrated the importance of core group members in gonorrhea transmission, in 1984, one New York State county changed its approach toward gonorrhea control by targeting its field intervention activities toward infected persons from a geographic core area. In late 1988, New York State experienced an epidemic increase in the number of syphilis casts. In response, the New York State sexually transmitted disease (STD) control program enacted a Syphilis Initiative, which required the diversion of field staff from gonorrhea to syphilis control activities for a 3-year period. Each of these events held the possibility of impacting gonorrhea incidence in this county. Goal of this Study: To evaluate the impact of core interventions on reducing gonorrhea incidence as compared to traditional nontargeted field intervention methods and to determine the influence on gonorrhea incidence of diverting field activities from gonorrhea to syphilis case finding. Study Design: A Poisson regression method was used to estimate gonorrhea incidence for a 22-year period in two similar counties: one county that used core intervention and one that applied traditional case-finding methods, The impact of core intervention was estimated in terms of the reduction in the gonorrhea incidence rate from the preintervention incidence rates. Results: After initiation of the core intervention, the relative risk of gonorrhea decreased by 61%. Between 30% to 40% of the total reported cases were interviewed for contacts annually during the intervention period. In the control county, the relative risk was reduced by 50% despite a significantly higher percentage of annual case interviews (60%-70%). In addition, a small change in the definition of core (from census tracts encompassing 50% of gonorrhea cases to 30%-35%) during the Syphilis Initiative led to a significant increase (16%) in the relative risk of gonorrhea. Conclusion: Targeting partner notification activities toward a geographic core area population appears effective in reducing the risk of gonorrhea, and it was more efficient because the overall percentage of casts interviewed was smaller than in a county using a nontargeted approach. Diversion of staff during a syphilis epidemic, combined with a narrowing of the geographic scope of the core intervention, was associated with an increase in gonorrhea incidence.