Table 1. ERGM specification for PWID contact network.

Parameter	Parameter Value
Edge	−8.384
Isolates	−9.308
Alternating-k-star	0.611
Alternating-k-triangle	1.707
Alternating-k-2-path	−0.563
Same location	2.111
Same gender	0.280
Same age<25	0.787
Same daily user freq.	0.429

Specification for the PWID contact network ERGM. The first five parameters model network structure while the last four model homophily effects: location (1, 2, 3), gender (M/F), age (less than 25, greater than 25), and injecting frequency (less than daily, at least daily). Positive homophily parameters indicate a propensity for two PWID to share a network tie when they have that attribute in common.