Yuridia Leyva

Publication Date



Sharing needles and ancillary injection drug equipment places injection drug users (IDU) at risk for Hepatitis C Virus (HCV), a highly infectious blood-borne virus. A limited number of studies have analyzed the per-contact infectivity of HCV associated with the use of previously-used needles, but per-contact infectivity of ancillary injecting equipment has not been previously investigated. Our goal is to estimate the per-contact infectivity of HCV associated with (1) injecting with another person's previously-used needle, classified as receptive needle sharing (RNS), and (2) using another person's previously-used ancillary injecting equipment, such as cookers to melt drugs and cottons to strain impurities from the melted drugs, termed receptive equipment sharing (RES). Estimates of per-contact probabilities were calculated based on self-reported exposures to RNS and RES. A probabilistic exposure model was used on the UFO (yoU Find Out) dataset composed of 784 IDU under the age of 30 who were surveyed quarterly between 2003-2008 and 2010-2014. For each participant, we selected the first survey with an HCV seronegative status up through their next seropositive survey, leaving us with 505 subjects on whom to conduct the analysis. A marginal maximum likelihood estimate (MLE) considering only RNS gives a per-contact infectivity of HCV as 0.39% (95% CI: 0.188% - 0.679%). A joint MLE gives RNS as 0.44% (95% CI: 0.0001% - 0.600%) and RES as 0% (95% CI: 0.00% - 0.69%), thus needles are a much bigger cause of concern than equipment. Though both probabilities are small, 13% (65/505) of the subjects studied seroconverted to an HCV-postitive status. Strategies for reducing RNS, and RES to a lesser extent, are important for reducing the spread of HCV and its related maladies.

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Level of Degree


Department Name

Mathematics & Statistics

First Committee Member (Chair)

Erik Barry Erhardt

Second Committee Member

Kimberly Ann Page

Third Committee Member

Gabriel Huerta




Maximum Likelihood, HCV, Hepatitis C Virus, per-contact infectivity, UFO Study, injection drug use, bootstrap

Document Type