Fig. 3

Public health interview continuum and network isolation. This figure shows the progress along the disease intervention specialist (DIS) interview continuum leading to isolation in the network. Upon receiving a positive test, the index case is contacted for public health interview. The interview has two parts, an assessment of risk and partner elicitation for contact tracing by a DIS; the index can refuse to disclose contacts. If the index agrees to disclose contacts then the DIS conducting the interview elicits all contacts who may be the source of infection or who may have acquired the infection from the index (“source” and “spread”). A DIS then determines whether there is enough identifying information on contacts to initiate the tracing process and attempts to locate contacts who have sufficient information so that they may be offered testing. Contact tracing for an index case can end at any point in this process, resulting in an index case having zero traced contacts. This chart depicts the contact tracing steps, the end result of contact tracing for each HIV index case (N = 569), and where constructing the network added context to HIV index cases with zero of their own traced partners by showing where the HIV index cases with zero of their own traced contacts were identified as persons of interest in HIV or syphilis contact tracing investigations conducted during the same time period in the same geographic area. Nearly half (273/569, 48%) of HIV indexes had no located contacts during contact tracing. However, by linking HIV and syphilis investigations from the same time period and area, 25 of these 273 (9%) indexes were identified by another network member which adds context to the local HIV epidemic and permits public health personnel to better understand transmission patterns