Impact of STD Mobile Clinics on Syphilis Incidence among Underserved Residents of Houston, TX: The Effects of Time and Space

Background: In response to an outbreak of syphilis, the city of Houston deployed two mobile clinics to provide testing to residents in underserved areas during 2007.

Objective: This study assesses the impact of this response on the incidence of syphilis as this program rolled out during the 2007 year.

Methods: Data are analyzed as a 3-level growth curve model using HLM.6. Level 1 includes population covariates of Race, Age, Sex and Time. Syphilis surveillance data by zip code for 14 months (1-month pre and post response) are used at Level 1. The Level 2 predictor is the relative demography of the zip codes and the duration of mobile unit presence. Level 3 tests the main effects on syphilis incidence.

Results: Results show that incidence of syphilis decreases as a function of time (beta=0.16; p=0.00, Level 1). The percent of African America/Black residents affects the number of syphilis incidence (beta=0.05; p=0.00, Level 2). The duration of mobile unit presence is related to a decrease in the incidence of syphilis in an area. The temporal decrease in syphilis in an area is related to mobile clinic impact (beta=0.001; p=0.00, Level 3).

Discussion: This study demonstrates the effectiveness of mobile units in responding to outbreaks of STIs. Longer duration in an area seems to be more effective than shorter but more frequent visits.

Conclusions: Incorporating mobile clinic operations into case-related and targeted screening activities allows HIV/STD prevention programs to reach underserved populations of residents whose access to such services is limited.